When editing a row in a GridView, I need a DropDownList whose list of available values depends on other column(s) in the row (let's just say the "type" of the record for now); that is, different options will be listed depending on which row is being edited.

I got it working after a fashion by adding an otherwise-unneeded DataKeyName to the GridView, but this is causing me grief elsewhere and anyway it feels too circuitous, so I'm looking for a better way. Here's how I'm currently doing it:

In .aspx file:

  ...
  
    ...
    
      
      
      
        
          
        
      
    
  
  ...

I wanted the SelectParameter to be a ControlParameter with ControlID="gvDct" and PropertyName="SelectedDataKey.Values[dctType]", but for unknown reasons that didn't work (the parameter values were null), so I added this bit to the .vb code-behind file to populate the row-specific parameter for the data source of the DropDownList:

Protected Sub sdsDctParent_Selecting(ByVal sender As Object, _
          ByVal e As System.Web.UI.WebControls.SqlDataSourceSelectingEventArgs)
  e.Command.Parameters(0).Value = gvDct.DataKeys(gvDct.EditIndex).Item(1)
End Sub

So, when I start editing a row in the GridView, the DropDownList is bound, which causes the SqlDataSource SelectCommand to execute, which fires the OnSelecting code where I provide the parameter value from the row being edited (EditIndex) so that I get the appropriate population of values in the DropDownList.

Is there a "better" way? The most important aspect for me is to avoid adding the DataKeyName, because that is causing me a too-many-parameters problem on the stored procedure I'm using to delete a row from the GridView.