public event ErrorEventHandler Error

Public Event Error As ErrorEventHandler

void reportViewer1_Error(object sender, Telerik.Reporting.ErrorEventArgs args)
{
    if (args.Exception is System.Exception) // check for a specific exception
    {
        var message = args.Exception.Message;
        // do something with the message and/or the 
    }
}

Private Sub reportViewer1_Error(sender As Object, args As Telerik.Reporting.ErrorEventArgs)
    If TypeOf args.Exception Is System.Exception Then
        ' check for a specific exception
        ' do something with the message and/or the 
        Dim message = args.Exception.Message
    End If
End Sub