Chris May

Dropdown1 has a SelectedValue which is invalid because it does not exist in the list of items.

'Dropdown1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value

This error has been a real pain to deal with. I finally have a work around and a guess at the underlying problem, and because I see that people are having this same problem I thought I would do a little writeup about it.

Obviously, if you look at the actual error message, there are cases when you can get this message and the problem is easy to solve. e.g. you have a dropdown populated with EmploID values and you try to databind with:

Value='<%# Bind("EmployeeName") %>

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

Categories: Programming | .Net | ASP.Net

Sunday, May 07, 2006 1:45:48 PM (Central Standard Time, UTC-06:00)

Comments [6] |

Thursday, August 23, 2007 11:22:22 AM (Central Standard Time, UTC-06:00)

Thanks for the suggestion. Manually binding the items in the DropDownList fixed this for me.

I had a State DropDownList in a MultiView that displayed the above error after editing one record and then re-selecting another record from a GridView via an edit command button.

So instead of this:
With ddlState
.Items.Clear()
.DataSource = ds
.DataValueField = "StateCode"
.DataTextField = "State"
.DataBind()
End With

I did this:
With ddlState
.Items.Clear()
For Each dr As MyWS.dsState.StateRow In ds.State.Rows
.Items.Add(New ListItem(dr.State.ToString, dr.StateCode.ToString))
Next
End With

Ken Palmer | kenpalmerAT NOSPAMhotmail dot com

Thursday, March 13, 2008 2:37:11 PM (Central Standard Time, UTC-06:00)

We had this happen to us too. Nothing changed. Was working fine. Did an IIS Reset and it fixed the problem. VERY weird. Thoughts?

Rob | rdalimonAT NOSPAMfideliscare dot org

Sunday, May 04, 2008 4:22:45 AM (Central Standard Time, UTC-06:00)

haha loved these lines :
) 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!!"

explained a lot to me.. was having the same problem in binding a datalist in expression web.... placing static options in the drop down would solve the problem but (100 records >< ) I need to learn how to code, and i can't understand much code in asp.net (just started yesterday)

anyway thanks!

JASnipes

Sunday, May 04, 2008 9:07:48 AM (Central Standard Time, UTC-06:00)

Glad I could help JASnipes

Chris | chrisAT NOSPAMchristophermayinc dot com

Thursday, July 10, 2008 4:48:19 PM (Central Standard Time, UTC-06:00)

I am having a similar issue, except that I believe I can solve it if I can figure out how to access the selectedvalue in the code behind.

I have two dropdowns that are visible under one condition and not under another. If I remove the selected value code runs well, of course when the visible one is displayed it does not select the needed element. So I believe if I could just trigger the selected value from the code behind when the visible condition is met I would be fine.

Can you guide me to which ever object, method, sqldatabind - what ever it may be called that will let me access the same value that would be placed in the BIND("something") call from a SqlDataSource select stored procedure.

Thanks so much for any direction!

swninetails | swninetailsAT NOSPAMhotmail dot com

Wednesday, August 27, 2008 9:30:59 PM (Central Standard Time, UTC-06:00)

Hi Chris,

I believe an easier solution is to search through the dropdownlist on databind, and select a default entry if your item isn't in the list for some reason.

Details here:

http://blog.evonet.com.au/post/dropdownlist1-has-a-SelectedValue-which-is-invalid-because-it-does-not-exist-in-the-list-of-items.aspx

Cheers,
Bartek

Bartek Marnane

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'Dropdown1' has a SelectedValue which is invalid because it does not exist in the list of items.Parameter name: value

'Dropdown1' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value