Public ReadOnly Property SheetTabIndex As Integer

Dim instance As SheetTabDoubleClickEventArgs
Dim value As Integer
 
value = instance.SheetTabIndex

public int SheetTabIndex {get;}

private void fpSpread1_SheetTabDoubleClick(object sender, FarPoint.Win.Spread.SheetTabDoubleClickEventArgs e)
{
    if(e.SheetTabIndex == 0)
    {
        e.Cancel = true;
    }
}

Private Sub FpSpread1_SheetTabDoubleClick(ByVal sender As Object, ByVal e As FarPoint.Win.Spread.SheetTabDoubleClickEventArgs)
Handles FpSpread1.SheetTabDoubleClick
    If e.SheetTabIndex = 0 Then
        e.Cancel = True
    End If
End Sub