Well of course that won’t work if all your values are integers and you are trying to set the value to “Bill Smith”.

 

But my problem was a bit more complicated.

 

I was building a web user control (aka ASCX) that was a “Location” dropdown.  The control basically contains a dropdown, and all the necessary logic to populate the dropdown, and I was trying to use this control inside the EditTemplate of a GridView.

 

To make things more complicated, in this case, I didn’t JUST want all the Locations, I also wanted to add a “Please Select” item to the list, with a value of 0.

 

But I kept getting the error above when the value was supposed to be 0.

 

I stepped through my code to try to find out what was going on.  I believe the issue is this:

 

On load, on value set, and on databind I call my “Populate” method.  This method sees if there are items in the dropdown.  If not, it gets a list from the database and binds to the dropdown.  It also checks if there is a “Please Select” item, and adds it if there isn’t one.

 

But still when Dropdown’s “DataBound” event was fired the last time, my manually added item had been removed.

 

So what I think what is happening is that :

1) I set the dropdown DataSource to a collection of business objects

2) I add the “Please Select” item

3) The dropdown is told to databind itself by the Gridview.

4) The dropdown says… “Oh, I do have a datasource, so I’m going to ditch my current list and rebind to that old collection”

5) The dropdown says “Holy shnikies, I am supposed to bind to value “0”, but I don’t have one!!”

 

I think there are 2 possible solutions.

 

1) I created an adapter class that only has Id and Description properties that are going to be used by the control, and I wrote a function to take my collection of business objects and build a collection of Adapters (adding my “Please Select”) to the list of adapters.  To see what I am talking about I will post this code below.

 

2) Manually add items to the dropdown instead of databinding, so that when the control is told to databind, it doesn’t have a datasource to use.

 

 

Here is my adapter code:

            '**** In my populate method
            Me.LocationsDropdown.DataSource = LocationAdapter.LocationsToAdapters(locations)
            Me.LocationsDropdown.DataTextField = "LocationDescriptionWithActiveAttribute"
            Me.LocationsDropdown.DataValueField = "LocationId"
            Me.LocationsDropdown.DataBind()



'*************************************
'*************************************




    Private Class LocationAdapter
        Public ciLocationId As Integer
        Public csLocationDescriptionWithActiveAttribute As String
        Public Property LocationId() As Integer
            Get
                Return ciLocationId
            End Get
            Set(ByVal value As Integer)
                Me.ciLocationId = Value
            End Set
        End Property

        Public Property LocationDescriptionWithActiveAttribute() As String
            Get
                Return csLocationDescriptionWithActiveAttribute
            End Get
            Set(ByVal value As String)
                Me.csLocationDescriptionWithActiveAttribute = Value
            End Set
        End Property

        Public Sub New(ByVal loc As Location)
            Me.LocationId = loc.LocationId
            Me.LocationDescriptionWithActiveAttribute = loc.LocationDescriptionWithActiveAttribute
        End Sub
        Public Sub New(ByVal Id As Integer, ByVal Desc As String)
            Me.LocationId = Id
            Me.LocationDescriptionWithActiveAttribute = Desc
        End Sub

        Public shared Function LocationsToAdapters(ByVal locations As List(Of Location)) As List(Of LocationAdapter)
            Dim adapters As New List(Of LocationAdapter)
            adapters.Add(New LocationAdapter(0, "--Location"))
            For Each loc As Location In locations
                adapters.Add(New LocationAdapter(loc))
            Next
            Return adapters
        End Function

    End Class