Visual Basic Q&A

Symptoms
In many applications there is a function to search and highlight keywordsin a text window. The RichTextBox control in Visual Basic can be madeto provide this functionality, as shown in the sample code below.
Resolution
Start a new project in Visual Basic. Form1 is created by default.Place a Command button and a RichTextBox on Form1. Set the Text propertyof the RichTextBox to “This is an example of finding text in a richtext box.”Add the following code to the General Declarations section of Form1:

Option ExplicitPrivate Sub Command1_Click()HighlightWords RichTextBox1, “text”, vbRedEnd SubPrivate Function HighlightWords(rtb As RichTextBox, _sFindString As String, _lColor As Long) _As IntegerDim lFoundPos As Long’Position of first character’of matchDim lFindLength As Long’Length of string to findDim lOriginalSelStart As LongDim lOriginalSelLength As LongDim iMatchCount As Integer’Number of matches’Save the insertion points current location and lengthlOriginalSelStart = rtb.SelStartlOriginalSelLength = rtb.SelLength’Cache the length of the string to findlFindLength = Len(sFindString)’Attempt to find the first matchlFoundPos = rtb.Find(sFindString, 0, , rtfNoHighlight)While lFoundPos > 0iMatchCount = iMatchCount + 1rtb.SelStart = lFoundPos’The SelLength property is set to 0 as’soon as you change SelStartrtb.SelLength = lFindLengthrtb.SelColor = lColor’Attempt to find the next matchlFoundPos = rtb.Find(sFindString, _lFoundPos + lFindLength, , rtfNoHighlight)Wend’Restore the insertion point to its original’location and lengthrtb.SelStart = lOriginalSelStartrtb.SelLength = lOriginalSelLength’Return the number of matchesHighlightWords = iMatchCountEnd Function Choose Start from the Run menu, or press the F5 key to start theproject. Click the Command button and you should see that bothoccurrences of the word “text” are now shown in red.

Symptoms
If you programmatically set the Text property for a data-bound member of the ComboBox control, the value typed in the text box portion of the ComboBox is displayed as expected. However, the Text property and the SelectedIndex property incorrectly return the value of the last item that was selected in the list box instead of returning the value typed in the text box.
When you type in the ComboBox at runtime, Text property returns the typed value, and SelectedIndex returns a value of -1.
Resolution
To resolve this problem, set the SelectedIndex property to -1 before you set the Text property for a data-bound member of the ComboBox, as in the following examples. Visual Basic .NET

ComboBox1.SelectedIndex = -1ComboBox1.Text = “My Text” Visual C# .NET

ComboBox1.SelectedIndex = -1;ComboBox1.Text = “My Text”; NOTE: Do not use the Text property to select a data-bound member of the ComboBox. You must locate the item in the list that you want to show, and then set the SelectedIndex to the index of the item. You do not have to set the Text property.
For example, if you bind the DisplayMember property and the ValueMember property of the ComboBox to a list that contains the numbers 1 through 10, and you want the ComboBox to display the number 5 in the text box and show 5 as selected in the list, you must set the SelectedIndex property to 5.

Symptoms
When you programmatically select the content of a text box, and the selected content resides in the area that you cannot see of the TEXTBOX control, then the text in the text box does not scroll automatically to display the selected text. Also, when you move to the TEXTBOX control by pressing TAB, the selected text does not appear automatically when the text box receives the focus.
Resolution
To work around this problem, you can use the ScrollToCaret method of the TEXTBOX control. This method scrolls the content of the control to the current caret position.
Copy the following code to the textBox1_Enter event:
Visual Basic Code

textBox1.ScrollToCaret()Visual C# Code

textBox1.ScrollToCaret();

Symptoms
A Standard EXE or UserControl form contains a second UserControl. The second UserControl contains a text box and a data control. You close all the forms and then open the second UserControl. When you attempt to change the DataSource property of the text box in the property window, the UserControl immediately closes or an application error occurs that causes Visual Basic to stop responding.
Resolution
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

Symptoms
Pressing the ESC key while the cursor is in the SQL text box of theGeneral Tab in the property page of the Remote Data Control causes a blankGeneral tab. When you click the Colors tab and then click the General tabagain, an application error occurs and Visual Basic ends. The SQL text boxcan be empty or contain characters. Clicking the Cancel button on thewindow correctly closes the window. This behavior only occurs under theWindows 95 operating system.To work around this behavior, programmatically set the properties ofremote data control or use the Properties window of the Remote Data Objectto set the properties.
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 Baseas it becomes available.

Symptoms
The Microsoft DataGrid Control 6.0 (OLEDB) does not return the contents ofan edited cell.
Using the CellText properties of the Column object returns the originalvalue of the text currently in the cell and not the text the user hasedited. This behavior differs from the Data Bound Grid Control that returnsthe value of the user-edited text.
This scenario may be problematic for a developer who would like to validatethe contents of the cell before the contents are placed in the recordset.
Resolution
The DataGrid control provides a window handle to the cell being edited.Using this handle and the GetWindowText API, the developer can get thecontents of the edited cell before the contents are saved in the recordset.