Visual Basic Q&A

Symptoms
An application error occurs when calling the Print method of a form objectcontained within a form array.
Resolution
To work around this problem, define a non-array form variable and set thevariable to reference the form array element that you want to manipulate.Once this variable has been initialized, you can safely call the Printmethod of the newly defined Form variable, as shown in the example below:

Private Sub Form_Load()Dim MyForm As FormDim fl(1) As Form2Set fl(0) = New Form2Set MyForm = fl(0)MyForm.Show’Show the Form2 formMyForm.Print ‘Print the form to the screenEnd Sub

Symptoms
When loading a form created by the Data Form Wizard, you may receive one ofthe following error messages:

Run-time error ‘-214217900 (80040e14)’, “Syntax error in FROM clause”
-or-

Run-time error ‘-214217904 (80040e10)’, “No value given for one or morerequired parameters”
Resolution
If the data source for a form created by the Data Form Wizard containsa dash ‘-’ in its name or in the name of a field, it is required that thedata source name or field name be delimited by brackets in a SQL statement.The Data Form Wizard does not include brackets around these names.

Symptoms
A form containing a bound Data Control disables the Validate event when theform is unloaded.
Resolution
Microsoft has confirmed this to be an issue in the Microsoft productslisted at the beginning of this article. Microsoft is researching thisissue and will post new information here in the Microsoft Knowledge Base asit becomes available.

Symptoms
You have a data-bound CheckedListBox control on your Windows Form. When you click to select some items in the CheckedListBox control at runtime and then you add a new row to the DataTable control that is bound to the CheckedListBox control, all the check boxes on the control are cleared.
Note Check boxes are not cleared when the CheckedListBox control is not data-bound.
Resolution
This problem occurs because the CheckedListBox control is not designed for data binding.

Symptoms
This article discusses how to validate a user’s Microsoft Windows user nameand passwordin a Microsoft Visual Basic .NETor Microsoft Visual Basic 2005 application. This article includes a code sample that validates a userin a VisualBasic .NET or Visual Basic 2005 application.
After the VisualBasic .NET or Visual Basic 2005 application validates the user’s Windows user name and password, the application also verifies that the Windows user has administrative credentials. The applicationperforms the validation by doing the following:The application passes the user name and password to the LogonUser function.The LogonUser function validates the user name and password and returns True if the user name and the password are valid.If the user name and password are valid, the LogonUser function receives a handle to the token that represents the Windows user.The WindowsIdentity object uses this token to represent the Windows user in the application.The WindowsPrincipal object uses the WindowsIdentity object to verify that the Windows user has administrative credentials.If the Windows user has administrative credentials, the application permits the Windows user to continue. If the Windows user does not have administrative credentials, the Windows user cannot continue and must quit the Visual Basic .NET application.
Resolution
This step-by-step article describes how to verify a user’s Windows user name and password in an application that you create by using Visual Basic .NET. This article also describes how to provide functionality to a Windows user based on the user rights that have been granted to the Windows user account.

RequirementsThis article assumes that you are familiar with the following topics: Windows applicationsVisual Basic .NET or Visual Basic 2005 programmingThe following list outlines the recommended hardware, software, network infrastructure, and service packs that you need:Microsoft Visual Studio .NET or Microsoft Visual Studio 2005Microsoft .NET FrameworkMicrosoft Windows Platform Software Development Kit (SDK)
Create a Visual Basic .NET or Visual Basic 2005 applicationTo create an application that verifies the user name and password, follow these steps: Start Visual Studio .NET or Visual Studio 2005.On the File menu, point to New, and then click Project. The New Project dialog box appears.Under Project Types, click Visual Basic Projects.
Note In Visual Studio 2005, click Visual Basic under Project Types.Under Templates, click Windows Application.In the Name box, type MyApp, and then click OK. By default, a Windows Form that is named Form1 is created.
Designthe Windows Form to implement validationYou can design the Windows Form to accept the user name and password at runtime by using TextBox controls. Then, you can make the application verify the Windows user’s user rights when the Windows user clicks a Button control. To do this, follow these steps: On the View menu, click Toolbox.In the Toolbox, double-click the TextBox control two times to add two TextBox controls to the Form1 form. By default, the TextBox1 TextBox control and the TextBox2 TextBox control are added to the Form1 form.Position the TextBox controls so that the TextBox2 TextBox control is below the TextBox1 TextBox control and is vertically aligned to the TextBox1 TextBox control.Right-click the TextBox2 TextBox control, and then click Properties.In the Properties window, set the PasswordChar property to *.In the Toolbox, double-click the Button control to add a Button control to the Form1 form. By default, the Button1 Button control is added to the Form1 form.Right-click the Button1 Button control, and then click Properties.In the Properties window, set the Text property to Validate User.In Solution Explorer, right-click MyApp, point to Add, and then click Add New Item. The Add New Item – MyApp dialog box appears.Under Templates, click Windows Form, and then click Open. By default, a Windows Form that is named Form2 is created.Add a Button control to the Form2 form. By default, the Button1 Button control is added to the Form2 form.Right-click the Button1 Button control, and then click Properties.In the Properties window, set the Text property to Add Numbers.In the Toolbox, double-click the Label control to add a Label control to the Form2 form. By default, the Label1 Label control is added to the Form2 form.Right-click the Label1 Label control, and then click Properties.In the Properties window, set the Size property to 200, 56.Double-click the Button1 Button control, and then add the following code to the Button1_Click event handler:

Dim firstnum, secondnum, result As Integerfirstnum = InputBox(“Enter the first number”)secondnum = InputBox(“Enter the second number”)result = firstnum + secondnumMessageBox.Show(“The sum of the two numbers is:” & result)
Write code to validate the Windows user in your Visual Basic .NET applicationYou can use the LogonUser Win32 API to verify the user name and password. The LogonUser function is declared in the Advapi32.dll library. You can call the LogonUser function from your Visual Basic .NET application by using the Declare statement.
You must pass the domain name, the user name, and the password to the LogonUser function. The LogonUser function validates the user by using these parameters and then returns a Boolean value. If the function succeeds, you receive a handle to a token that represents the Windows user. The WindowsIdentity object uses this token to represent the Windows user in your Visual Basic .NET or Visual Basic 2005 application. The WindowsPrincipal object uses this WindowsIdentity object to verify the Windows user’s user rights.
To write code that implements validation in your Visual Basic .NET or Visual Basic 2005 application, follow these steps: In Solution Explorer, right-click Form1.vb, and then click View Code.Add the following code at the top of the Form1 form:

Imports System.Security.PrincipalImports System.Security.PermissionsImports System.Runtime.InteropServicesImports System.EnvironmentLocate the following code:

End ClassAdd the following code before the code that you located in step 3:

‘The LogonUser function tries to log on to the local computer ‘by using the specified user name. The function authenticates ‘the Windows user with the password provided.Private Declare Auto Function LogonUser Lib “advapi32.dll” (ByVal lpszUsername As [String], _ByVal lpszDomain As [String], ByVal lpszPassword As [String], _ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _ByRef phToken As IntPtr) As Boolean’The FormatMessage function formats a message string that is passed as input.<DllImport(“kernel32.dll”)> _Public Shared Function FormatMessage(ByVal dwFlags As Integer, ByRef lpSource As IntPtr, _ByVal dwMessageId As Integer, ByVal dwLanguageId As Integer, ByRef lpBuffer As [String], _ByVal nSize As Integer, ByRef Arguments As IntPtr) As IntegerEnd Function’The CloseHandle function closes the handle to an open object such as an Access token.Public Declare Auto Function CloseHandle Lib “kernel32.dll” (ByVal handle As IntPtr) As BooleanLocate the following code:

End ClassAdd the following code before the code that you located in step 5:

‘The GetErrorMessage function formats and then returns an error message’that corresponds to the input error code.Public Shared Function GetErrorMessage(ByVal errorCode As Integer) As StringDim FORMAT_MESSAGE_ALLOCATE_BUFFER As Integer = &H100Dim FORMAT_MESSAGE_IGNORE_INSERTS As Integer = &H200Dim FORMAT_MESSAGE_FROM_SYSTEM As Integer = &H1000Dim msgSize As Integer = 255Dim lpMsgBuf As StringDim dwFlags As Integer = FORMAT_MESSAGE_ALLOCATE_BUFFER Or FORMAT_MESSAGE_FROM_SYSTEM Or FORMAT_MESSAGE_IGNORE_INSERTSDim lpSource As IntPtr = IntPtr.ZeroDim lpArguments As IntPtr = IntPtr.Zero’Call the FormatMessage function to format the message.Dim returnVal As Integer = FormatMessage(dwFlags, lpSource, errorCode, 0, lpMsgBuf, _msgSize, lpArguments)If returnVal = 0 ThenThrow New Exception(“Failed to format message for error code ” + errorCode.ToString() + “. “)End IfReturn lpMsgBufEnd FunctionIn Solution Explorer, right-click Form1.vb, and then click View Designer.Double-click the Button1 Button control, and then add the following code to the Button1_Click event handler:

Dim tokenHandle As New IntPtr(0)TryDim UserName, MachineName, Pwd As String’The MachineName property gets the name of your computer.MachineName = System.Environment.MachineNameUserName = TextBox1.TextPwd = TextBox2.TextDim frm2 As New Form2Const LOGON32_PROVIDER_DEFAULT As Integer = 0Const LOGON32_LOGON_INTERACTIVE As Integer = 2tokenHandle = IntPtr.Zero’Call the LogonUser function to obtain a handle to an access token.Dim returnValue As Boolean = LogonUser(UserName, MachineName, Pwd, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, tokenHandle)If returnValue = False Then’This function returns the error code that the last unmanaged function returned.Dim ret As Integer = Marshal.GetLastWin32Error()Dim errmsg As String = GetErrorMessage(ret)frm2.Show()frm2.Label1.Text = errmsgfrm2.Button1.Visible = FalseElse’Create the WindowsIdentity object for the Windows user account that is’represented by the tokenHandle token.Dim newId As New WindowsIdentity(tokenHandle)Dim userperm As New WindowsPrincipal(newId)’Verify whether the Windows user has administrative credentials.If userperm.IsInRole(WindowsBuiltInRole.Administrator) Thenfrm2.Button1.Text = “Add Numbers”frm2.Label1.Text = “Click this button to add two numbers”frm2.Show()Elsefrm2.Label1.Text = ” You do not have administrative credentials.”frm2.Button1.Visible = Falsefrm2.Show()End IfEnd If’Free the access token.If Not System.IntPtr.op_Equality(tokenHandle, IntPtr.Zero) ThenCloseHandle(tokenHandle)End IfCatch ex As ExceptionMessageBox.Show(“Exception occurred. ” + ex.Message)End Try
Verify that your Visual Basic .NET application worksTo verify that the validation has completed correctly, follow these steps: On the Build menu, click Build Solution.On the Debug menu, click Start.In the TextBox1 box, type a user name.In the TextBox2 box, type a password.Click Validate User.

Symptoms
To sum the fields in a Microsoft Windows Forms DataGrid control and then to display the calculated totals in a footer, you must first create a user control that inherits from the System.Windows.Forms.DataGrid class. Then you must handle the events that are raised when a cell in this user control is changed.
You must disable the default sorting feature of the DataGrid control to prevent the footer row from being sorted. To implement custom sorting for your DataGrid control, you must handle the MouseDown event.
You must also disable the footer row of the DataGrid control to prevent users from editing the cells of the footer row. To provide data for the event that prevents users from editing the cells of the DataGrid control, you must define an event arguments class, and then you must define a class that contains methods to paint and to disable the footer row.
To sum the fields and to display the calculated totals in a footer, build the DataGrid control, add an instance of the DataGrid control to a Windows Application project, bind the DataGrid control to the related data, and then build and run the application.
Resolution
This step-by-step article describes how to sum the fields in a Windows Forms DataGrid control by using Microsoft Visual Basic .NET. This article also describes how to customize the Windows Forms DataGrid control to display the calculated totals in a footer.

RequirementsThis article assumes that you are familiar with the following topics: The Windows Forms DataGrid controlData binding by using Windows Forms and Microsoft ADO.NETHandling and raising events
The following list outlines the recommended hardware, software, network infrastructure, and service packs that you need:Microsoft Windows 2000, Microsoft Windows XP, or Microsoft Windows Server 2003Microsoft Visual Studio .NET
Create a Windows Control Library projectStart Visual Studio .NET.On the File menu, point to New, and then click Project. The New Project dialog box appears.Under Project Types, click Visual Basic Projects.Under Templates, click Windows Control Library.In the Name box, type DataGridControl, and then click OK. By default, a user control that is named UserControl1 is created.On the View menu, click Solution Explorer.In Solution Explorer, right-click UserControl1.vb, and then click Rename.Rename the UserControl1.vb file as DataGridControlVB.vb.
Inherit from the Windows Forms DataGrid control, and then add variables, properties, and methodsIn Solution Explorer, right-click DataGridControlVB.vb, and then click View Code.Import the required namespaces, and then declare a delegate for the event that disables the cells of the DataGrid control. To do this, add the following code at the top of the code window:

Imports SystemImports System.CollectionsImports System.ComponentModelImports System.DrawingImports System.DataImports System.Data.SqlClientImports System.Windows.FormsImports System.Text’ Declare a delegate for the event that disables the cells of the DataGrid control.Public Delegate Sub DataGridDisableCellEventHandler _(ByVal sender As System.Object, ByVal e As DataGridDisableCellEventArgs)Locate the following code:

Public Class UserControl1Inherits System.Windows.Forms.UserControlMake your Windows Forms DataGrid control inherit from the System.Windows.Forms.DataGrid class. To do this, replace the code that you located in step 3 with the following code:

Public Class DataGridControlVBInherits System.Windows.Forms.DataGridAdd the following variable declarations after the code that you added in step 4:

‘ Declare private variables for your DataGrid control.Private RowCount As IntegerPrivate ColCount As IntegerPrivate SortedColNum As IntegerPrivate Ascending As BooleanPrivate CellValueChanged As BooleanPrivate SourceTable As StringPrivate MyDataView As DataViewPrivate MyDataSet As DataSetPrivate MyDataRow As DataRowPrivate SummaryCols As ArrayListPrivate CurrentDataGridCellLocation As DataGridCellPrivate WithEvents MyDataTable As DataTablePrivate Shared FooterBackColor As BrushPrivate Shared FooterForeColor As BrushLocate the following code comment in the “Windows Form Designer generated code” area:

‘Add any initialization after the InitializeComponent() callPerform custom initialization in the constructor of your Windows Forms DataGrid control. To do this, replace the code comment that you located in step 6 with the following code:

RowCount = 0ColCount = 0CellValueChanged = FalseAscending = FalseMyDataRow = NothingMyDataTable = New DataTable(“NewTable”)CurrentDataGridCellLocation = New DataGridCellSummaryCols = New ArrayListLocate the following code:

#End RegionAdd the following property definitions after the code that you located in step 8:

Public WriteOnly Property GridDataSet() As DataSetSet(ByVal Value As DataSet)MyDataSet = ValueEnd SetEnd PropertyPublic Property SummaryColumns() As ArrayListGetReturn SummaryColsEnd GetSet(ByVal Value As ArrayList)SummaryCols = ValueEnd SetEnd PropertyPublic Property DataSourceTable() As StringGetReturn SourceTableEnd GetSet(ByVal Value As String)SourceTable = ValueEnd SetEnd PropertyPublic Shared Property FooterColor() As BrushGetReturn FooterBackColorEnd GetSet(ByVal Value As Brush)FooterBackColor = ValueEnd SetEnd PropertyPublic Shared Property FooterFontColor() As BrushGetReturn FooterForeColorEnd GetSet(ByVal Value As Brush)FooterForeColor = ValueEnd SetEnd PropertyDisable the default sorting feature of the DataGrid control to prevent the footer row from being sorted. To do this, and to bind the custom DataGrid control to the related data, add the following code after the code that you added in step 9:

Public Sub BindDataGrid()MyDataTable = MyDataSet.Tables(0)MyDataView = MyDataTable.DefaultViewMe.DataSource = MyDataViewDim TableStyle As DataGridTableStyle = New DataGridTableStyleTableStyle.MappingName = SourceTable’ Add a Boolean data type column to the DataTable object.’ You can use this column during your custom sorting.MyDataTable.Columns.Add(“ID”, System.Type.GetType(“System.Boolean”))MyDataTable.Columns(“ID”).DefaultValue = FalseMyDataTable.Columns(“ID”).ColumnMapping = MappingType.HiddenColCount = MyDataTable.Columns.Count’ Create a footer row for the DataTable object.MyDataRow = MyDataTable.NewRow()’ Set the footer value as an empty string for all columns that contains string values.Dim MyIterator As IntegerFor MyIterator = 0 To ColCount – 1If (MyDataTable.Columns(MyIterator).DataType.ToString() = “System.String”) ThenMyDataRow(MyIterator) = “”End IfNext’ Add the footer row to the DataTable object.MyDataTable.Rows.Add(MyDataRow)RowCount = MyDataTable.Rows.Count’ Add a MyDataGridTextBox control to each cell of the DataGrid control.Dim TempDataGridTextBox As MyDataGridTextBoxFor MyIterator = 0 To ColCount – 2TempDataGridTextBox = New MyDataGridTextBox(MyIterator)TempDataGridTextBox.HeaderText = MyDataTable.Columns(MyIterator).ColumnNameTempDataGridTextBox.MappingName = MyDataTable.Columns(MyIterator).ColumnNameAddHandler TempDataGridTextBox.DataGridDisableCell, _New DataGridDisableCellEventHandler(AddressOf SetEnableValues)’ Disable the default sorting feature of the DataGrid control.TableStyle.AllowSorting = FalseTableStyle.GridColumnStyles.Add(TempDataGridTextBox)NextMe.TableStyles.Add(TableStyle)Me.DataSource = MyDataViewMyDataView.ApplyDefaultSort = FalseMyDataView.AllowNew = False’ Set the value of the footer cell.Dim MyCell As DataGridCell = New DataGridCellMyCell.RowNumber = MyDataTable.Rows.Count – 1′ Calculate the value for each of the cells in the footer.Dim MyArray(2) As StringDim MyString As StringFor Each MyString In SummaryColsMyArray = MyString.Split(“,”c)MyCell.ColumnNumber = Convert.ToInt32(MyArray(0))Me(MyCell) = MyDataTable.Compute(MyArray(1), “ID is null”).ToString()NextEnd Sub
Handle the events that are raised when a cell in the DataGrid control is changedYou must handle the ColumnChanged event of the DataTable object, and then you must handle the CurrentCellChanged event of the DataGrid control to track when a cell value in the DataGrid control is changed. To do this, follow these steps: Handle the ColumnChanged event of the DataTable object. To do this, add the following code after the code that you added in step 10 of the “Inherit from the Windows Forms DataGrid control, and then add variables, properties, and methods” section:

‘ Handle the DataTable object’s ColumnChanged event’ to track whether the value in a cell has changed.Private Sub MyDataTable_ColumnChanged(ByVal sender As Object, _ByVal e As System.Data.DataColumnChangeEventArgs) Handles MyDataTable.ColumnChangedDim Row As Integer, Col As IntegerRow = 0Col = 0′ Determine the row that contains the changed cell.Dim TempDataRow As DataRowFor Each TempDataRow In MyDataTable.RowsIf (TempDataRow.Equals(e.Row)) ThenCurrentDataGridCellLocation.RowNumber = RowCellValueChanged = TrueExit ForRow = Row + 1End IfNext’ Determine the column that contains the changed cell.Dim TempDataColumn As DataColumnFor Each TempDataColumn In MyDataTable.ColumnsIf (TempDataColumn.Equals(e.Column)) ThenCurrentDataGridCellLocation.ColumnNumber = ColCellValueChanged = TrueExit ForCol = Col + 1End IfNextEnd SubHandle the CurrentCellChanged event of the DataGrid control. To do this, add the following code after the code that you added in step 1:

‘ Handle the CurrentCellChanged event of the DataGrid control.Private Sub DataGridControlVB_CurrentCellChanged(ByVal sender As Object, _ByVal e As System.EventArgs) Handles MyBase.CurrentCellChangedIf (CellValueChanged = True) ThenDim MyCell As DataGridCell = New DataGridCellMyCell.RowNumber = MyDataTable.Rows.Count – 1′ Calculate the value for each cell in the footer.Dim MyArray(2) As StringDim MyString As StringFor Each MyString In SummaryColsMyArray = MyString.Split(“,”)MyCell.ColumnNumber = Convert.ToInt32(MyArray(0))Me(MyCell) = MyDataTable.Compute(MyArray(1), “ID is null”).ToString()NextEnd IfCellValueChanged = FalseEnd Sub
Handle the MouseDown event of the DataGrid control to implement custom sortingBecause you have disabled the default sorting feature of the DataGrid control, you must perform custom sorting when a user clicks a column header. You must handle the MouseDown event of the DataGrid control to implement custom sorting.
To do this, add the following event handler after the code that you added in step 2 of the “Handle the events that are raised when a cell in the DataGrid control is changed” section:

‘ Handle the MouseDown event to perform custom sorting.Private Sub DataGridControlVB_MouseDown(ByVal sender As Object, _ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDownDim MyHitTestInfo As DataGrid.HitTestInfoMyHitTestInfo = Me.HitTest(e.X, e.Y)Dim ColName As StringIf (MyHitTestInfo.Type = DataGrid.HitTestType.ColumnHeader) ThenDim ColNum As Integer = MyHitTestInfo.ColumnIf (ColNum <> -1) ThenColName = MyDataTable.Columns(ColNum).ColumnName’ Perform custom sorting. To do this, always sort the Boolean data type column in’ ascending order so that the footer row stays at the end.Dim MyChar() As Char = {“↑”c, “↓”c}Dim NewString As String = _Me.TableStyles(0).GridColumnStyles(SortedColNum).HeaderText.TrimEnd(MyChar).Trim()Me.TableStyles(0).GridColumnStyles(SortedColNum).HeaderText = NewStringIf (Ascending = True) ThenMyDataView.Sort = “ID Asc,” + ColName + ” desc”Ascending = FalseMe.TableStyles(0).GridColumnStyles(ColNum).HeaderText = _Me.TableStyles(0).GridColumnStyles(ColNum).HeaderText + ” ↑”SortedColNum = ColNumElseMyDataView.Sort = “ID Asc,” + ColName + ” asc”Ascending = TrueMe.TableStyles(0).GridColumnStyles(ColNum).HeaderText = _Me.TableStyles(0).GridColumnStyles(ColNum).HeaderText + ” ↓”SortedColNum = ColNumEnd IfEnd IfEnd IfEnd Sub
Disable the footer row of the DataGrid controlTo disable the footer row of the DataGrid control, add the following code after the code that you added in the “Handle the MouseDown event of the DataGrid control to implement custom sorting” section:

‘ Disable the footer row of the DataGrid control.Public Sub SetEnableValues(ByVal sender As Object, ByVal e As DataGridDisableCellEventArgs)If (e.Row = RowCount – 1) Thene.EnableValue = FalseElsee.EnableValue = TrueEnd IfEnd Sub
Define an event arguments class that provides data for the DataGridDisableCell eventTo define an event arguments class that provides data for the DataGridDisableCell event, follow these steps: In the Form1.vb file, locate the following code:

End ClassAdd the following code after the code that you located in step 1:

‘ Define a custom event arguments class that inherits from the EventArgs class.Public Class DataGridDisableCellEventArgsInherits EventArgsPrivate MyCol As IntegerPrivate MyRow As IntegerPrivate MyEnableValue As BooleanPublic Sub New(ByVal Row As Integer, ByVal Col As Integer)MyRow = RowMyCol = ColMyEnableValue = TrueEnd SubPublic Property Column() As IntegerGetReturn MyColEnd GetSet(ByVal Value As Integer)MyCol = ValueEnd SetEnd PropertyPublic Property Row() As IntegerGetReturn MyRowEnd GetSet(ByVal Value As Integer)MyRow = ValueEnd SetEnd PropertyPublic Property EnableValue() As BooleanGetReturn MyEnableValueEnd GetSet(ByVal Value As Boolean)MyEnableValue = ValueEnd SetEnd PropertyEnd Class
Define a class that contains methods to paint and to disable the footer rowTo define a class that contains methods to paint and to disable the footer row, add the following code after the code that you added in step 2 of the “Define an event arguments class that provides data for the DataGridDisableCell event” section:

Public Class MyDataGridTextBoxInherits DataGridTextBoxColumn’ Declare an event for the DataGridDisableCellEventHandler delegate that you have defined.Public Event DataGridDisableCell As DataGridDisableCellEventHandlerPrivate MyCol As Integer’ Save the column number of the column to add the MyDataGridTextBox control to.Public Sub New(ByVal Column As Integer)MyCol = ColumnEnd Sub’ Override the Paint method to set colors for the footer row.Protected Overloads Overrides Sub Paint(ByVal g As System.Drawing.Graphics, _ByVal bounds As System.Drawing.Rectangle, ByVal source As System.Windows.Forms.CurrencyManager, _ByVal rowNum As Integer, ByVal backBrush As System.Drawing.Brush, _ByVal foreBrush As System.Drawing.Brush, ByVal alignToRight As Boolean)’ Initialize the event arguments by using the number’ of the current row and the current column.Dim e As New DataGridDisableCellEventArgs(rowNum, MyCol)’ Raise the DataGridDisableCell event.RaiseEvent DataGridDisableCell(Me, e)’ Set the foreground color and the background color for the footer row.If Not e.EnableValue ThenIf DataGridControlVB.FooterColor Is Nothing _Or DataGridControlVB.FooterFontColor Is Nothing ThenbackBrush = Brushes.WhiteforeBrush = Brushes.BlackElsebackBrush = DataGridControlVB.FooterColorforeBrush = DataGridControlVB.FooterFontColorEnd IfEnd If’ Call the Paint event of the DataGridTextBoxColumn class.MyBase.Paint(g, bounds, source, rowNum, backBrush, foreBrush, alignToRight)End Sub’ Override the Edit method to disable the footer row.Protected Overloads Overrides Sub Edit(ByVal source As System.Windows.Forms.CurrencyManager, _ByVal rowNum As Integer, ByVal bounds As System.Drawing.Rectangle, ByVal readOnlyFlag As Boolean, _ByVal instantText As String, ByVal cellIsVisible As Boolean)Dim e As DataGridDisableCellEventArgs = Nothing’ Initialize the event arguments by using the number’ of the current row and the current column.e = New DataGridDisableCellEventArgs(rowNum, MyCol)’ Raise the DataGridDisableCell event.RaiseEvent DataGridDisableCell(Me, e)’ Call the Edit event of the DataGridTextBoxColumn’ class for all rows other than the footer row.If e.EnableValue ThenMyBase.Edit(source, rowNum, bounds, readOnlyFlag, instantText, cellIsVisible)End IfEnd SubEnd Class
Save the DataGridControlVB.vb file, and then build the DataGrid controlOn the File menu, click Save DataGridControlVB.vb As. The Save File As dialog box appears.Click the arrow next to the Save button, and then click Save with Encoding. You receive a message to replace the existing DataGridControlVB.vb file.Click Yes. The Advanced Save Options dialog box appears.In the Encoding box, select Unicode (UTF-8 with signature) – Codepage 65001, and then click OK.On the Build menu, click Build DataGridControl to build the DataGridControl.dll assembly.
Create a Windows Application project that uses the DataGrid controlIn Solution Explorer, right-click the DataGridControl solution, point to Add, and then click New Project. The Add New Project dialog box appears.Under Project Types, click Visual Basic Projects.Under Templates, click Windows Application.In the Name box, type TestApplication, and then click OK. By default, a Windows Form that is named Form1 is created.In Solution Explorer, right-click TestApplication, and then click Set as StartUp Project.On the View menu, click Toolbox.Do one of the following, depending on the version of Visual Studio .NET that you have:If you are using Visual Studio .NET 2003, click Add/Remove Toolbox Items on the Tools menu. If you are using Visual Studio .NET 2002, click Customize Toolbox on the Tools menu.The Customize Toolbox dialog box appears.On the .NET Framework Components tab, click Browse. The Open dialog box appears.Locate and then click the DataGridControl.dll assembly that you created in step 5 of the “Save the DataGridControlVB.vb file, and then build the DataGrid control” section.Click Open, and then click OK. The DataGridControlVB control is added to the Toolbox.In the Toolbox, double-click the DataGridControlVB control to add the DataGridControlVB1 control to the Form1 form.Click Form1.On the View menu, click Properties Window to view the Properties window for the Form1 form.Set the Size property to 450, 200.In the Design view of the Form1 form, click the DataGridControlVB1 control.On the View menu, click Properties Window to view the Properties window for the DataGridControlVB1 control.Set the Size property to 420, 115.
Bind the custom DataGrid control to the related dataIn Solution Explorer, right-click Form1.vb, and then click View Code.Import the required namespaces. To do this, add the following code at the top of the code window:

Imports System.DataImports System.Data.SqlClientLocate the following code:

Public Class Form1Inherits System.Windows.Forms.FormAdd the following variable declarations after the code that you located in step 3:

Dim MyConnString As StringDim MyDataSet As DataSet = NothingDim MyDataAdapter As SqlDataAdapter = NothingDim MyConn As SqlConnectionBind the DataGrid control to the related data. To do this, add the following code after the “Windows Form Designer generated code” area.
Note In the following code, replace <ServerName> with the appropriate value for an instance of Microsoft SQL Server:

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.LoadDim SqlString As String = “SELECT * FROM discounts”MyConnString = “server=<ServerName>;Integrated Security=SSPI;database=pubs”MyConn = New SqlConnection(MyConnString)MyDataAdapter = New SqlDataAdapter(SqlString, MyConn)MyDataSet = New DataSetTryMyDataAdapter.Fill(MyDataSet, “discounts”)’ Specify the dataset that you want your DataGrid control to use.DataGridControlVB1.GridDataSet = MyDataSet’ Specify the source table that you want your DataGrid control to use.DataGridControlVB1.DataSourceTable = “discounts”‘ Add the columns that you want to sum to an array list. Use the following format:’ “<ColumnNumber>,summing expression”Dim Summary As New ArrayListSummary.Add(“2,sum(lowqty)”)Summary.Add(“3,sum(highqty)”)’ Map the array list to the SummaryColumns property of your DataGrid control.DataGridControlVB1.SummaryColumns = Summary’ Set the foreground color and the background color for the footer row.DataGridControlVB1.FooterColor = Brushes.BlueVioletDataGridControlVB1.FooterFontColor = Brushes.White’ Bind the DataGrid control to the related data.DataGridControlVB1.BindDataGrid()’ Dispose the data adapter, and then close the connection.Catch DatabaseException As SqlExceptionMessageBox.Show(“Database exception: ” & DatabaseException.Message)Catch OtherException As ExceptionMessageBox.Show(OtherException.Message)FinallyMyDataAdapter.Dispose()MyConn.Dispose()End TryEnd Sub
Complete code listingDataGridControlVB.vb

Imports SystemImports System.CollectionsImports System.ComponentModelImports System.DrawingImports System.DataImports System.Data.SqlClientImports System.Windows.FormsImports System.Text’ Declare a delegate for the event that disables the cells of the DataGrid control.Public Delegate Sub DataGridDisableCellEventHandler _(ByVal sender As System.Object, ByVal e As DataGridDisableCellEventArgs)Public Class DataGridControlVBInherits System.Windows.Forms.DataGrid’ Declare private variables for your DataGrid control.Private RowCount As IntegerPrivate ColCount As IntegerPrivate SortedColNum As IntegerPrivate Ascending As BooleanPrivate CellValueChanged As BooleanPrivate SourceTable As StringPrivate MyDataView As DataViewPrivate MyDataSet As DataSetPrivate MyDataRow As DataRowPrivate SummaryCols As ArrayListPrivate CurrentDataGridCellLocation As DataGridCellPrivate WithEvents MyDataTable As DataTablePrivate Shared FooterBackColor As BrushPrivate Shared FooterForeColor As Brush#Region ” Windows Form Designer generated code “Public Sub New()MyBase.New()’This call is required by the Windows Form Designer.InitializeComponent()RowCount = 0ColCount = 0CellValueChanged = FalseAscending = FalseMyDataRow = NothingMyDataTable = New DataTable(“NewTable”)CurrentDataGridCellLocation = New DataGridCellSummaryCols = New ArrayListEnd Sub’UserControl1 overrides dispose to clean up the component list.Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)If disposing ThenIf Not (components Is Nothing) Thencomponents.Dispose()End IfEnd IfMyBase.Dispose(disposing)End Sub’Required by the Windows Form DesignerPrivate components As System.ComponentModel.IContainer’NOTE: The following procedure is required by the Windows Form Designer’It can be modified using the Windows Form Designer.’Do not modify it using the code editor.<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()components = New System.ComponentModel.ContainerEnd Sub#End RegionPublic WriteOnly Property GridDataSet() As DataSetSet(ByVal Value As DataSet)MyDataSet = ValueEnd SetEnd PropertyPublic Property SummaryColumns() As ArrayListGetReturn SummaryColsEnd GetSet(ByVal Value As ArrayList)SummaryCols = ValueEnd SetEnd PropertyPublic Property DataSourceTable() As StringGetReturn SourceTableEnd GetSet(ByVal Value As String)SourceTable = ValueEnd SetEnd PropertyPublic Shared Property FooterColor() As BrushGetReturn FooterBackColorEnd GetSet(ByVal Value As Brush)FooterBackColor = ValueEnd SetEnd PropertyPublic Shared Property FooterFontColor() As BrushGetReturn FooterForeColorEnd GetSet(ByVal Value As Brush)FooterForeColor = ValueEnd SetEnd PropertyPublic Sub BindDataGrid()MyDataTable = MyDataSet.Tables(0)MyDataView = MyDataTable.DefaultViewMe.DataSource = MyDataViewDim TableStyle As DataGridTableStyle = New DataGridTableStyleTableStyle.MappingName = SourceTable’ Add a Boolean data type column to the DataTable object.’ You can use this column during your custom sorting.MyDataTable.Columns.Add(“ID”, System.Type.GetType(“System.Boolean”))MyDataTable.Columns(“ID”).DefaultValue = FalseMyDataTable.Columns(“ID”).ColumnMapping = MappingType.HiddenColCount = MyDataTable.Columns.Count’ Create a footer row for the DataTable object.MyDataRow = MyDataTable.NewRow()’ Set the footer value as an empty string for all columns that contains string values.Dim MyIterator As IntegerFor MyIterator = 0 To ColCount – 1If (MyDataTable.Columns(MyIterator).DataType.ToString() = “System.String”) ThenMyDataRow(MyIterator) = “”End IfNext’ Add the footer row to the DataTable object.MyDataTable.Rows.Add(MyDataRow)RowCount = MyDataTable.Rows.Count’ Add a MyDataGridTextBox control to each cell of the DataGrid control.Dim TempDataGridTextBox As MyDataGridTextBoxFor MyIterator = 0 To ColCount – 2TempDataGridTextBox = New MyDataGridTextBox(MyIterator)TempDataGridTextBox.HeaderText = MyDataTable.Columns(MyIterator).ColumnNameTempDataGridTextBox.MappingName = MyDataTable.Columns(MyIterator).ColumnNameAddHandler TempDataGridTextBox.DataGridDisableCell, _New DataGridDisableCellEventHandler(AddressOf SetEnableValues)’ Disable the default sorting feature of the DataGrid control.TableStyle.AllowSorting = FalseTableStyle.GridColumnStyles.Add(TempDataGridTextBox)NextMe.TableStyles.Add(TableStyle)Me.DataSource = MyDataViewMyDataView.ApplyDefaultSort = FalseMyDataView.AllowNew = False’ Set the value of the footer cell.Dim MyCell As DataGridCell = New DataGridCellMyCell.RowNumber = MyDataTable.Rows.Count – 1′ Calculate the value for each of the cells in the footer.Dim MyArray(2) As StringDim MyString As StringFor Each MyString In SummaryColsMyArray = MyString.Split(“,”c)MyCell.ColumnNumber = Convert.ToInt32(MyArray(0))Me(MyCell) = MyDataTable.Compute(MyArray(1), “ID is null”).ToString()NextEnd Sub’ Handle the DataTable object’s ColumnChanged event’ to track if the value in a cell has changed.Private Sub MyDataTable_ColumnChanged(ByVal sender As Object, _ByVal e As System.Data.DataColumnChangeEventArgs) Handles MyDataTable.ColumnChangedDim Row As Integer, Col As IntegerRow = 0Col = 0′ Determine the row that contains the changed cell.Dim TempDataRow As DataRowFor Each TempDataRow In MyDataTable.RowsIf (TempDataRow.Equals(e.Row)) ThenCurrentDataGridCellLocation.RowNumber = RowCellValueChanged = TrueExit ForRow = Row + 1End IfNext’ Determine the column that contains the changed cell.Dim TempDataColumn As DataColumnFor Each TempDataColumn In MyDataTable.ColumnsIf (TempDataColumn.Equals(e.Column)) ThenCurrentDataGridCellLocation.ColumnNumber = ColCellValueChanged = TrueExit ForCol = Col + 1End IfNextEnd Sub’ Handle the CurrentCellChanged event of the DataGrid control.Private Sub DataGridControlVB_CurrentCellChanged(ByVal sender As Object, _ByVal e As System.EventArgs) Handles MyBase.CurrentCellChangedIf (CellValueChanged = True) ThenDim MyCell As DataGridCell = New DataGridCellMyCell.RowNumber = MyDataTable.Rows.Count – 1′ Calculate the value for each of the cells in the footer.Dim MyArray(2) As StringDim MyString As StringFor Each MyString In SummaryColsMyArray = MyString.Split(“,”)MyCell.ColumnNumber = Convert.ToInt32(MyArray(0))Me(MyCell) = MyDataTable.Compute(MyArray(1), “ID is null”).ToString()NextEnd IfCellValueChanged = FalseEnd Sub’ Handle the MouseDown event to perform custom sorting.Private Sub DataGridControlVB_MouseDown(ByVal sender As Object, _ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDownDim MyHitTestInfo As DataGrid.HitTestInfoMyHitTestInfo = Me.HitTest(e.X, e.Y)Dim ColName As StringIf (MyHitTestInfo.Type = DataGrid.HitTestType.ColumnHeader) ThenDim ColNum As Integer = MyHitTestInfo.ColumnIf (ColNum <> -1) ThenColName = MyDataTable.Columns(ColNum).ColumnName’ Perform custom sorting. To do this, always sort the Boolean data type column in’ ascending order so that the footer row stays at the end.Dim MyChar() As Char = {“↑”c, “↓”c}Dim NewString As String = _Me.TableStyles(0).GridColumnStyles(SortedColNum).HeaderText.TrimEnd(MyChar).Trim()Me.TableStyles(0).GridColumnStyles(SortedColNum).HeaderText = NewStringIf (Ascending = True) ThenMyDataView.Sort = “ID Asc,” + ColName + ” desc”Ascending = FalseMe.TableStyles(0).GridColumnStyles(ColNum).HeaderText = _Me.TableStyles(0).GridColumnStyles(ColNum).HeaderText + ” ↑”SortedColNum = ColNumElseMyDataView.Sort = “ID Asc,” + ColName + ” asc”Ascending = TrueMe.TableStyles(0).GridColumnStyles(ColNum).HeaderText = _Me.TableStyles(0).GridColumnStyles(ColNum).HeaderText + ” ↓”SortedColNum = ColNumEnd IfEnd IfEnd IfEnd Sub’ Disable the footer row of the DataGrid control.Public Sub SetEnableValues(ByVal sender As Object, ByVal e As DataGridDisableCellEventArgs)If (e.Row = RowCount – 1) Thene.EnableValue = FalseElsee.EnableValue = TrueEnd IfEnd SubEnd Class’ Define a custom event arguments class that inherits from the EventArgs class.Public Class DataGridDisableCellEventArgsInherits EventArgsPrivate MyCol As IntegerPrivate MyRow As IntegerPrivate MyEnableValue As BooleanPublic Sub New(ByVal Row As Integer, ByVal Col As Integer)MyRow = RowMyCol = ColMyEnableValue = TrueEnd SubPublic Property Column() As IntegerGetReturn MyColEnd GetSet(ByVal Value As Integer)MyCol = ValueEnd SetEnd PropertyPublic Property Row() As IntegerGetReturn MyRowEnd GetSet(ByVal Value As Integer)MyRow = ValueEnd SetEnd PropertyPublic Property EnableValue() As BooleanGetReturn MyEnableValueEnd GetSet(ByVal Value As Boolean)MyEnableValue = ValueEnd SetEnd PropertyEnd ClassPublic Class MyDataGridTextBoxInherits DataGridTextBoxColumn’ Declare an event for the DataGridDisableCellEventHandler delegate that you have defined.Public Event DataGridDisableCell As DataGridDisableCellEventHandlerPrivate MyCol As Integer’ Save the column number of the column to add the MyDataGridTextBox control to.Public Sub New(ByVal Column As Integer)MyCol = ColumnEnd Sub’ Override the Paint method to set colors for the footer row.Protected Overloads Overrides Sub Paint(ByVal g As System.Drawing.Graphics, _ByVal bounds As System.Drawing.Rectangle, ByVal source As System.Windows.Forms.CurrencyManager, _ByVal rowNum As Integer, ByVal backBrush As System.Drawing.Brush, _ByVal foreBrush As System.Drawing.Brush, ByVal alignToRight As Boolean)’ Initialize the event arguments with the number’ of the current row and the current column.Dim e As New DataGridDisableCellEventArgs(rowNum, MyCol)’ Raise the DataGridDisableCell event.RaiseEvent DataGridDisableCell(Me, e)’ Set the foreground color and the background color for the footer row.If Not e.EnableValue ThenIf DataGridControlVB.FooterColor Is Nothing _Or DataGridControlVB.FooterFontColor Is Nothing ThenbackBrush = Brushes.WhiteforeBrush = Brushes.BlackElsebackBrush = DataGridControlVB.FooterColorforeBrush = DataGridControlVB.FooterFontColorEnd IfEnd If’ Call the Paint event of the DataGridTextBoxColumn class.MyBase.Paint(g, bounds, source, rowNum, backBrush, foreBrush, alignToRight)End Sub’ Override the Edit method to disable the footer row.Protected Overloads Overrides Sub Edit(ByVal source As System.Windows.Forms.CurrencyManager, _ByVal rowNum As Integer, ByVal bounds As System.Drawing.Rectangle, ByVal readOnlyFlag As Boolean, _ByVal instantText As String, ByVal cellIsVisible As Boolean)Dim e As DataGridDisableCellEventArgs = Nothing’ Initialize the event arguments with the number’ of the current row and the current column.e = New DataGridDisableCellEventArgs(rowNum, MyCol)’ Raise the DataGridDisableCell event.RaiseEvent DataGridDisableCell(Me, e)’ Call the Edit event of the DataGridTextBoxColumn’ class for all rows other than the footer row.If e.EnableValue ThenMyBase.Edit(source, rowNum, bounds, readOnlyFlag, instantText, cellIsVisible)End IfEnd SubEnd ClassForm1.vbNote In the following code, replace <ServerName> with the appropriate value for an instance of Microsoft SQL Server.

Imports System.DataImports System.Data.SqlClientPublic Class Form1Inherits System.Windows.Forms.FormDim MyConnString As StringDim MyDataSet As DataSet = NothingDim MyDataAdapter As SqlDataAdapter = NothingDim MyConn As SqlConnection#Region ” Windows Form Designer generated code “Public Sub New()MyBase.New()’This call is required by the Windows Form Designer.InitializeComponent()’Add any initialization after the InitializeComponent() callEnd Sub’Form overrides dispose to clean up the component list.Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)If disposing ThenIf Not (components Is Nothing) Thencomponents.Dispose()End IfEnd IfMyBase.Dispose(disposing)End Sub’Required by the Windows Form DesignerPrivate components As System.ComponentModel.IContainer’NOTE: The following procedure is required by the Windows Form Designer’It can be modified using the Windows Form Designer.’Do not modify it using the code editor.Friend WithEvents DataGridControlVB1 As DataGridControl.DataGridControlVB<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()Me.DataGridControlVB1 = New DataGridControl.DataGridControlVBCType(Me.DataGridControlVB1, System.ComponentModel.ISupportInitialize).BeginInit()Me.SuspendLayout()”DataGridControlVB1′Me.DataGridControlVB1.DataMember = “”Me.DataGridControlVB1.DataSourceTable = NothingMe.DataGridControlVB1.HeaderForeColor = System.Drawing.SystemColors.ControlTextMe.DataGridControlVB1.Location = New System.Drawing.Point(0, 0)Me.DataGridControlVB1.Name = “DataGridControlVB1″Me.DataGridControlVB1.Size = New System.Drawing.Size(420, 115)Me.DataGridControlVB1.TabIndex = 0”Form1′Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)Me.ClientSize = New System.Drawing.Size(442, 173)Me.Controls.Add(Me.DataGridControlVB1)Me.Name = “Form1″Me.Text = “Form1″CType(Me.DataGridControlVB1, System.ComponentModel.ISupportInitialize).EndInit()Me.ResumeLayout(False)End Sub#End RegionPrivate Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.LoadDim SqlString As String = “SELECT * FROM discounts”MyConnString = “server=<ServerName>;Integrated Security=SSPI;database=pubs”MyConn = New SqlConnection(MyConnString)MyDataAdapter = New SqlDataAdapter(SqlString, MyConn)MyDataSet = New DataSetTryMyDataAdapter.Fill(MyDataSet, “discounts”)’ Specify the dataset that you want your DataGrid control to use.DataGridControlVB1.GridDataSet = MyDataSet’ Specify the source table that you want your DataGrid control to use.DataGridControlVB1.DataSourceTable = “discounts”‘ Add the columns that you want to sum to an array list in the following format:’ “<ColumnNumber>,summing expression”Dim Summary As New ArrayListSummary.Add(“2,sum(lowqty)”)Summary.Add(“3,sum(highqty)”)’ Map the array list to the SummaryColumns property of your DataGrid control.DataGridControlVB1.SummaryColumns = Summary’ Set the foreground color and the background color for the footer row.DataGridControlVB1.FooterColor = Brushes.BlueVioletDataGridControlVB1.FooterFontColor = Brushes.White’ Bind the DataGrid control to the related data.DataGridControlVB1.BindDataGrid()’ Dispose the data adapter, and then close the connection.Catch DatabaseException As SqlExceptionMessageBox.Show(“Database exception: ” & DatabaseException.Message)Catch OtherException As ExceptionMessageBox.Show(OtherException.Message)FinallyMyDataAdapter.Dispose()MyConn.Dispose()End TryEnd SubEnd Class
Build and then run your applicationOn the Build menu, click Build Solution.On the Debug menu, click Start.
The Form1 form appears. Your custom DataGrid control is present on the Form1 form. The footer row of the DataGrid control contains the sums of the values of the fields that you specified to sum. You cannot edit the footer row. However, when you change the value in any one of the cells, the corresponding footer cell is updated.