How To Execute SQL Parameterized Stored Procedures by Using the ODBC .NET Provider and Visual Basic .NET (309486)

SUMMARY

This step-by-step describes how to call a parameterized SQL Server stored procedure using the ODBC .NET Managed Provider and Visual Basic .NET.

Although executing a parameterized stored procedure using the ODBC .NET Provider is slightly different from executing the same procedure using the SQL or the OLE DB Provider, there is one important difference -- the stored procedure must be called using the ODBC CALL syntax rather than the name of the stored procedure. For additional information on this CALL syntax, see the page entitled "Procedure Calls" in the ODBC Programmer's Reference in the MSDN Library.

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Call Syntax Examples

1. Here is an example of the call syntax for an actual stored procedure in the Northwind sample database that expects one input parameter:

   {CALL CustOrderHist (?)}
   					

2. Here is an example of the call syntax for a stored procedure that expects one input parameter and returns one output parameter and a return value. The first placeholder represents the return value:

   {? = CALL Procedure1 (?, ?)
   					

3. The ODBC .NET Managed Provider, like the OLE DB Provider, processes parameters by ordinal position (zero-based) and not by name.

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1. If you have not already done so, download and install the ODBC .NET Managed Provider from the following Microsoft Web site:

   http://www.microsoft.com/downloads/release.asp?ReleaseID=35715

2. Start Visual Studio .NET, and then create a new Visual Basic .NET Windows Application.
3. On the Project menu, click Add Reference. On the .Net tab, double-click Microsoft.Data.ODBC.dll to add a reference to the Microsoft.Data.ODBC namespace.
4. At the very top of the code window, add the following statement:

   Imports Microsoft.Data.ODBC
   					

5. Add a command button to the default form from the Toolbox.
6. Double-click the command button to switch to the code window for the button Click event. Paste the following code in the Click event procedure, adjusting the SQL Server connection string as necessary:

           Dim cn As OdbcConnection
   
           Try
               cn = New OdbcConnection("Driver={SQL Server};Server=(local);Database=Northwind;Trusted_Connection=Yes")
   
               Dim cmd As OdbcCommand = New OdbcCommand("{call CustOrderHist (?)}", cn)
   
               Dim prm As OdbcParameter = cmd.Parameters.Add("@CustomerID", OdbcType.Char, 5)
               prm.Value = "ALFKI"
   
               cn.Open()
   
               Dim dr As OdbcDataReader = cmd.ExecuteReader()
   
               While dr.Read
                   Console.WriteLine(dr.GetString(0))
               End While
               dr.Close()
   
           Catch o As OdbcException
   
               MsgBox(o.Message.ToString)
   
           Finally
   
               cn.Close()
   
           End Try
   					

7. Run the project. This code calls the "CustOrderHist" stored procedure, passing in the CustomerID as a single input parameter, and returns a resultset. In the Output window, you should see the list of products ordered by Northwind customer ALFKI.

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1. Using Query Analyzer, create the following stored procedure in the Northwind sample database. This stored procedure accepts a CustomerID as an input parameter and returns a list of orders placed by the customer, returns the average freight per order paid by that customer as an output parameter, and returns the number of orders placed by the customer as a return value.

   CREATE PROCEDURE usp_TestParameters
   @CustID CHAR(5),
   @AvgFreight MONEY OUTPUT
   AS
   SELECT @AvgFreight = AVG(Freight) FROM Orders WHERE CustomerID = @CustID
   SELECT * FROM Orders WHERE CustomerID = @CustID
   RETURN @@ROWCOUNT
   					

2. Repeat steps 1 through 6 above, substituting the following code in the Click event procedure of the command button:

           Dim cn As OdbcConnection
   
           Try
               cn = New OdbcConnection("Driver={SQL Server};Server=(local);Database=Northwind;Trusted_Connection=Yes")
   
               Dim cmd As OdbcCommand = New OdbcCommand("{? = call usp_TestParameters (?, ?)}", cn)
   
               Dim prm As OdbcParameter = cmd.Parameters.Add("@RETURN_VALUE", OdbcType.Int)
               prm.Direction = ParameterDirection.ReturnValue
   
               prm = cmd.Parameters.Add("@CustomerID", OdbcType.Char, 5)
               prm.Value = "ALFKI"
   
               prm = cmd.Parameters.Add("@AvgFreight", OdbcType.Double)
               prm.Direction = ParameterDirection.Output
   
               cn.Open()
   
               Dim dr As OdbcDataReader = cmd.ExecuteReader()
   
               While dr.Read
                   Console.WriteLine(dr.GetString(0))
               End While
               dr.Close()
   
               Console.WriteLine("Average Freight (output param): {0}", cmd.Parameters(2).Value)
               Console.WriteLine("Order Count (return value): {0}", cmd.Parameters(0).Value)
   
   
           Catch o As OdbcException
   
               MsgBox(o.Message.ToString)
   
           Finally
   
               cn.Close()
   
           End Try
   					

3. Run the project. This code calls the "usp_TestParameters" stored procedure that we created in step 1 above, passing in the CustomerID as a single input parameter, and returns a resultset, an output parameter and a return value. In the Output window, you should see the list of orders placed by Northwind customer ALFKI, the average freight the customer paid per order, and the count of orders.

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1. The ADO syntax that is usually used to call stored procedures, where the name of the procedure alone is provided as the CommandText, cannot be used with the ODBC .NET Managed Provider.
2. When a stored procedure returns a resultset, the output parameter(s) and return value are not available until the resultset has been accessed and closed. For example, if we omitted the line "dr.Close()" in the second sample above, we would be unable to retrieve the values for the output parameter and the return value.
3. The ODBC .NET Managed Provider, like the OLE DB Provider, processes parameters by ordinal position (zero-based) and not by name.
4. The ODBC .NET Managed Provider does not ship with Visual Studio .NET, but must be downloaded separately.

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