Question

I have a DataGrid bound to a DataView which, among other columns has, an ID Column and ParentID Column, I need the user to be able to specify a ParentID using using a DropDownList (ComboBox).

Now, I have already added the DropDownList to the DataGrid like this:

<Columns>
    [...]
    <asp:TemplateColumn HeaderText="Parent" >
        <ItemTemplate>
            <asp:DropDownList ID="ddlParentID" 
                              runat="server" 
                              DataValueField="ID"
                              DataTextField="Short_Description"
                              Width="100%"
                              DataSource="<%# dsDV %> ">
            </asp:DropDownList>
        </ItemTemplate>
    </asp:TemplateColumn>
</Columns>

In the code-behind I have the following a method:

Protected dsDV As New DataView
Protected Sub PopulateDropDownList()
    Dim conn As SqlClient.SqlConnection = New SqlClient.SqlConnection(myConnString)
    Dim comm As SqlClient.SqlCommand = New SqlClient.SqlCommand("SELECT * FROM myTable", conn)
    comm.CommandType = CommandType.Text
    Dim myTableTable As New DataTable
    conn.Open()

    myTableTable.Load(comm.ExecuteReader)
    Me.dsDV = myTableTable.DefaultView
End Sub

That PopulateDropDownMethod is called on the form Load Event but, albeit DDLs do show, they show empty, as if no DataBinding is being made.

How can I properly bind the DDL with a dataSource in the codebehind? Or, if that’s not the issue, how do I properly fill the DDL?

Update 1

After the first answer I went ahead and tried this (still no luck):

Protected Sub dg_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) Handles dgData.ItemDataBound
    If e.Item.ItemType = ListItemType.Item Or e.Item.ItemType = ListItemType.AlternatingItem Then
        Dim ddl As DropDownList = CType(e.Item.Cells(3).FindControl("ddlParentID"), DropDownList)
        Me.PopulateDropDownList(ddl)
    End If
End Sub

Protected dsDV As New DataView
Protected Sub PopulateDropDownList(ddl As DropDownList)
    Dim conn As SqlClient.SqlConnection = New SqlClient.SqlConnection(myConnString)
    Dim comm As SqlClient.SqlCommand = New SqlClient.SqlCommand("SELECT * FROM myTable", conn)
    comm.CommandType = CommandType.Text
    Dim myTableTable As New DataTable
    conn.Open()

    myTableTable.Load(comm.ExecuteReader)
    ddl.DataSource = myTableTable.DefaultView
    ddl.DataBind()
End Sub

Note that I also removed the call to PopulateDropDownList from the Form Load Event handler.

Answer 1

I don’t why but taking the binding code from the aspx to the aspx.vb fixed the issue, so it all looks like this now:

<asp:TemplateColumn HeaderText="Parent" >
    <ItemTemplate>
        <asp:DropDownList ID="ddlParentID" runat="server" Width="100%" >
        </asp:DropDownList>
    </ItemTemplate>
</asp:TemplateColumn>

And for the code-behind, for each row:

Dim ddl As DropDownList = CType(e.Item.Cells(3).FindControl("ddlParentID"), DropDownList)
ddl.DataValueField = "ID"
ddl.DataTextField = "Short_Description"
ddl.DataSource = myTable.DefaultView
ddl.DataBind()