BUG: The Text property of a data-bound ComboBox returns an incorrect value when you set the value in code

Visual Basic .NET

ComboBox1.SelectedIndex = -1
ComboBox1.Text = "My Text"
				

Visual C# .NET

ComboBox1.SelectedIndex = -1;
ComboBox1.Text = "My Text";
				

Back to the top

Steps to Reproduce the Behavior

1. Create a new Visual Basic .NET or Visual Basic 2005 Windows application.
   
   By default, Form1 is created.
2. Add an \fbox command, add a TextBox control, and then add a Button control to Form1.
3. Open a Code window on Form1.
4. Paste the following code into the Code window below the Windows Form Designer Generated Code section:

       Private Sub Form1_Load(ByVal sender As System.Object, _
           ByVal e As System.EventArgs) Handles MyBase.Load
           ' Create a DataTable on which to bind the ComboBox.
           Dim myDT As New DataTable()
   
           Dim myCOL1 As DataColumn = New DataColumn()
           Dim myCOL2 As DataColumn = New DataColumn()
   
           myCOL1.ColumnName = "ContactName"
           myCOL2.ColumnName = "ContactID"
   
           myCOL1.DataType = System.Type.GetType("System.String")
           myCOL2.DataType = System.Type.GetType("System.Int32")
   
           myDT.Columns.Add(myCOL1)
           myDT.Columns.Add(myCOL2)
   
           ' Populate the DataTable.
           Dim myDR As DataRow
   
           myDR = myDT.NewRow
           myDR.Item(0) = "North"
           myDR.Item(1) = 0
           myDT.Rows.Add(myDR)
   
           myDR = myDT.NewRow()
           myDR.Item(0) = "South"
           myDR.Item(1) = 1
           myDT.Rows.Add(myDR)
   
           myDR = myDT.NewRow()
           myDR.Item(0) = "East"
           myDR.Item(1) = 2
           myDT.Rows.Add(myDR)
   
           ' Bind the ComboBox.
           ComboBox1.DataSource = myDT
           ComboBox1.DisplayMember = "ContactName"
           ComboBox1.ValueMember = "ContactID"
       End Sub
   
       Private Sub Button1_Click(ByVal sender As System.Object, _
         ByVal e As System.EventArgs) Handles Button1.Click
           ComboBox1.Text = "Hello!"
           MessageBox.Show(ComboBox1.Text)
       End Sub
   					

   Note You must change the code in Visual Basic 2005. By default, Visual Basic creates two files for the project when you create a Windows Forms project. If the form is named Form1, the two files that represent the form are named Form1.vb and Form1.Designer.vb. You write the code in the Form1.vb file. The Windows Forms Designer writes the code in the Form1.Designer.vb file. The Windows Forms Designer uses the partial keyword to divide the implementation of Form1 into two separate files. This behavior prevents the designer-generated code from being interspersed with your code.
   
   For more information about the new Visual Basic 2005 language enhancements, visit the following Microsoft Developer Network (MSDN) Web site:
   http://msdn2.microsoft.com/en-us/library/ms379584(vs.80).aspx (http://msdn2.microsoft.com/en-us/library/ms379584(vs.80).aspx)
   For more information about partial classes and the Windows Forms Designer, visit the following MSDN Web site:
   http://msdn2.microsoft.com/en-us/library/ms171843.aspx (http://msdn2.microsoft.com/en-us/library/ms171843.aspx)
5. Run the application, and then click the Button control.
   
   The Text property value that is returned is equal to the selected item in the ComboBox, and is not equal to the value that was set programmatically.

Back to the top