In a VB.net application, retrieving variables from a database, if the value was null, it would cause the error, “Conversion from type ‘DBNull’ to type ‘String’ is not valid”.  A work-around to stop this error was to create a function that would evaluate the imported database variable for a null value as an object then convert it to a string for use without error in your code.

Here is the VB.net code:


Function checkNull(Byval variable as object) as String
If IsDBNull(varialbe) Then
Return("")
Else
Return (variable)
End If
End Function


Conversion from type ‘DBNull’ to type ‘String’ is not valid is a post from: WebPaws.com

Inside a modalpopupextender panel, you need to add and set the UseSubmitBehavior to false for the OK/Cancel controls to be enabled with postback to behave outside of the ajax control.

Example:

<asp:LinkButton ID="OkButton" runat="server" Text="Button Text" UseSubmitBehavior="false" PostBackUrl="product.aspx?id=3" />


You can also use OnClick in the button to perform an action outside of ajax with UseSubmitBehavior=”false”.

Allow page redirect from an asp:linkbutton in an Ajax ModalPopupExtender is a post from: WebPaws.com