I have run into this problem many times where a form that has controls bound to a bindingsource. Sometimes after a build if the form is currently displayed or after making some kind of change you open the form in the designer it will throw errors telling you that the binding source is either not declared or not assigned. Closing the form and recompiling ussually make this go away and the form can be opened in the designer.

I found an interesting solution/cause of this error. It has to do with where you set the datasource for the bindingsource.

If you set the datasource in the forms load event then this error can occurr.

Code Snippet

Private Sub form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

bindingsource1.datasource=dataset1.table1

End Sub

If you set the datasource before calling the .show method the error does nothappen.

Code Snippet

Dim Form As New Form1

With Form1

.BiddingSource1.DataSource = dataset1.table1

form1.show

End With

I have no idea why this is but it has stopped this annoying problem in all my projects.

Just an FYI for all as I have searched for an answer to this and found nothing on the net.