Symptoms
Output parameters do not appear to be initialized or return a wrong value when executing an ADO.NET command.
Resolution
This problem can occur for the following reasons: Output parameters are returned at the end of the data stream when using a DataReader object.The Direction property of the parameter is not set properly.
Symptoms
This sample in this article demonstrates how to retrieve an XML document from SQL Server 2000 by using a template file that contains parameters.More specifically, a query is issued against SQL Server 2000 by using an ActiveX Data Objects (ADO) 2.6 command stream. This query fetches the XML DataStream.
This sample reads the “products.xml” template file from disk and sets thecommand text for the ADODB.Command object for the query to run.
You must set the following properties for the Properties collection of the ADODB.Command object:Base Path. This property establishes the location of the template and the Extensible Style Sheet Language (XSL) files.Output Stream. This property designates where the resulting XML data stream will be piped.Dialect. The dialect defines the syntax and the general rules that the provider uses to parse the string or the stream. By setting the command language dialect, you specify how the Microsoft OLE DB Provider for SQL Server interprets the command text that is received from ADO. The dialect is specified by a globally unique identifier (GUID) and is set by using the Dialect property of the Command object.XSL. This property transforms the XML document.NOTE: Output Stream may be any object that supports an IStream or ISequentialStream interface. Objects that support the IStream interfaces are the ADODB.Stream object, the Microsoft Internet Information Services (IIS) 5.0 Response object, and a Microsoft XML (MSXML) DomDocument object.
Resolution
Create a new Standard EXE project in Visual Basic. Form1 is created by default.On the Project menu, click Components, and then add a reference to both Microsoft Internet Controls and Microsoft ActiveX Data Objects 2.6.Add a Web browser to the form, name it WebBrowser1, and then size it accordingly.Add a frame to the form, and place two option buttons in it. Name the first button optXSLYes with the caption XSL Yes, and then name the second button optXSLNo with the caption XSL No.Add two command buttons. Name the first button cmdTestIt with the caption Test, and then name the second button cmdExitProgram with the caption Exit.Paste the following Visual Basic code in the Code window of the form:
Option ExplicitConst DBGUID_DEFAULT As String = “{C8B521FB-5CF3-11CE-ADE5-00AA0044773D}” Private Sub cmdExitProgram_Click()Unload MeEndEnd SubPrivate Sub cmdTestIt_Click()Dim cn As New ADODB.ConnectionDim cmd As New ADODB.CommandDim cmdStream As New ADODB.StreamDim cmdOutput As New ADODB.StreamDim txtOutputFileName As String’ open the database connectioncn.Open “provider=sqloledb;data source=.;initial catalog=northwind;uid=sa;pwd=”‘ open the command stream that will eventually contain the templated querycmdStream.Open’ set the character set to asciicmdStream.Charset = “ascii”‘ set the command stream type to text, not binary.cmdStream.Type = adTypeText’ read the template file from disk into the command stream to executecmdStream.LoadFromFile App.Path & “\products.xml”‘ set the command connectionSet cmd.ActiveConnection = cn’ set the command’s command stream to hook the template query to the command you want to run.Set cmd.CommandStream = cmdStream’ set the command dialectcmd.Dialect = DBGUID_DEFAULT’ open the output stream to receive the results for the command execute.cmdOutput.Open’ set the base path for where the template file resides.’ Currently, this must point to a file on disk. Remote templates via’ http://…template.xml” are not allowed.cmd.Properties(“Base Path”) = App.Path’ set up the output stream that will receive the output of the command execute.cmd.Properties(“Output Stream”) = cmdOutput’ set the XSL to process if the user requested the output to be fixed.If optXSLYes Then’ set the file name for the XSL: this inherits the “base path” settingcmd.Properties(“XSL”) = “products.xsl”‘ set the file extension to “.htm”, mainly so the Web browser displays’ set the output as a table.Try with a “.xml” extension… what is displayed?txtOutputFileName = App.Path & “\queryout.htm”ElsetxtOutputFileName = App.Path & “\queryout.xml”End If’ execute the command stream with the settings specified above.cmd.Execute , , adExecuteStream’ position the stream back to the beginning: the “file position” in the’stream will be at the end of the stream.Writing to a stream will append’on the end and only while the output from the command execute generates.cmdOutput.Position = 0’save the output to a file, this is only needed to use the navigate on the Web browser controlcmdOutput.SaveToFile txtOutputFileName, adSaveCreateOverWrite’ Navigate/display the results of the command executes.WebBrowser1.Navigate txtOutputFileName’ close and clean-up the objects used.cmdOutput.ClosecmdStream.Closecn.CloseSet cmdOutput = NothingSet cmdStream = NothingSet cmd = NothingSet cn = NothingEnd Sub To create a template file, create a new text file, paste the following template into the file, and then save it with a name of products.xml:
<?xml version=’1.0′ ?><root xmlns:sql=”urn:schemas-microsoft-com:xml-sql”><sql:header><sql:param name=”ProdName”>%</sql:param></sql:header><sql:query>SELECT*FROMProductsWHEREProductName like ‘%’ + @ProdName + ‘%’ORDER BYProductNameFOR XML AUTO</sql:query></root> As an option, create a file named products.xsl with the following code to transform the output:
<?xml version=’1.0′ ?><xsl:stylesheet xmlns:xsl=”http://www.w3.org/TR/WD-xsl”><xsl:template match=”/”><html><head><title>MSDN ADO Product Sample with SQL Server 2000 Features</title><base href=”http://localhost/3tier/” /></head><body><table border=”0″ cellPadding=”1″ cellSpacing=”1″width=”100%”style=”COLOR:black;FONT-FAMILY:Arial;FONT-SIZE:12pt.;FONT-WEIGHT:500″><tr bgColor=”#336699″ align=”center”><TD><P ><STRONG><FONT color=”white” size=”2″>Product ID:</FONT></STRONG></P></TD><TD><P ><STRONG><FONT color=”white” size=”2″>Product Name:</FONT></STRONG></P></TD><TD><P ><STRONG><FONT color=”white” size=”2″>Unit Price:</FONT></STRONG></P></TD><TD><P ><STRONG><FONT color=”white” size=”2″>Units In Stock:</FONT></STRONG></P></TD><TD><P ><STRONG><FONT color=”white” size=”2″>Restock Level:</FONT></STRONG></P></TD><TD><P ><FONT color=”white” size=”2″><STRONG>Units On Order:</STRONG></FONT></P></TD></tr><xsl:for-each select=”root/Products”><tr style=”COLOR: black; FONT-FAMILY: Arial; FONT-SIZE: 0.8em; FONT-WEIGHT: 500″><td bgColor=”#F0F0F0″><xsl:value-of select=”@ProductID”/></td><td bgColor=”#F0F0F0″><xsl:value-of select=”@ProductName”/></td><td bgColor=”#F0F0F0″><xsl:value-of select=”@UnitPrice”/></td><td bgColor=”#F0F0F0″><xsl:value-of select=”@UnitsInStock”/></td><td bgColor=”#F0F0F0″><xsl:value-of select=”@ReorderLevel”/></td><td bgColor=”#F0F0F0″><xsl:value-of select=”@UnitsOnOrder”/></td></tr></xsl:for-each></table></body></html></xsl:template></xsl:stylesheet>
Symptoms
If you run an ADODB command stream and specify SQL SELECT with the FOR XML AUTO clause, an XML document stream is fetched from SQL Server and displayed in the Visual Basic Intermediate window.
You must set the following properties for the Properties collection of the ADODB.Command object: Output Stream. This property designates where the resulting XML data stream will be piped.Dialect. The dialect defines the syntax and the general rules that the provider uses to parse the string or the stream. By setting the command language dialect, you specify how the Microsoft OLE DB Provider for SQL Server interprets the command text that is received from ActiveX Data Objects (ADO). The dialect is specified by a globally unique identifier (GUID) and is set by using the Dialect property of the Command object.
Resolution
Create a new Visual Basic Standard EXE. Form1 is created by default. On the Project menu, select References, and then set a reference to Microsoft ActiveX Data Objects 2.6.Place a CommandButton on Form1, and then place the following code in its click event:
Note You must change User ID=<username> and Password=<strong password> to the correct values before you run this code. Make sure that the User ID has the appropriate permissions to perform this operation on the database.
Private Sub Command1_Click()Dim sConn As StringDim sQuery As StringDim outStrmsConn = “Provider=SQLOLEDB;Data Source=.;Initial Catalog=Northwind;User ID=<username>;Password=<strong password>;”Dim adoConn As ADODB.ConnectionSet adoConn = New ADODB.ConnectionadoConn.ConnectionString = sConnadoConn.CursorLocation = adUseClientadoConn.OpenDim adoCmd As ADODB.CommandSet adoCmd = New ADODB.CommandSet adoCmd.ActiveConnection = adoConnsQuery = “<ROOT xmlns:sql=’urn:schemas-microsoft-com:xml-sql’>”sQuery = sQuery & “<sql:query>SELECT * FROM PRODUCTS FOR XML AUTO</sql:query>”’sQuery = sQuery & “</ROOT>”Dim adoStreamQuery As ADODB.StreamSet adoStreamQuery = New ADODB.Stream’Open the command stream so it may be written toadoStreamQuery.Open’Set the input command stream’s text with the query stringadoStreamQuery.WriteText sQuery, adWriteChar’Reset the position in the stream, otherwise it will be at EOS.adoStreamQuery.Position = 0′Set the command object’s command to the input stream set above.Set adoCmd.CommandStream = adoStreamQuery’Set the dialect for the command stream to be a SQL query.adoCmd.Dialect = “{5D531CB2-E6Ed-11D2-B252-00C04F681B71}”‘Create the output stream to stream the results into.Set outStrm = CreateObject(“ADODB.Stream”)outStrm.Open’Set command’s output stream to the output stream just opened.adoCmd.Properties(“Output Stream”) = outStrm’Execute the command, thus filling the output stream.adoCmd.Execute , , adExecuteStream’Position the output stream back to the beginning of the stream.outStrm.Position = 0′Create temporary string.Dim str As String’Assign the stream’s output to the temp string to format.str = outStrm.ReadText(-1)’Add a cr/lf pair for each row in the result stream.str = Replace(str, “><”, “>” & vbCrLf & “<”)Debug.Print strGoTo ByeRecError:Debug.Print Err.Number & “: ” & Err.DescriptionBye:Set adoCmd = NothingIf adoConn.State = adStateOpen ThenadoConn.CloseEnd IfSet adoConn = NothingEnd Sub Specify either the SQL 2000 Server or, if the server is on your local machine, use the period symbol (.) or (local). Note that the Immediate window of Visual Basic displays the results.