Input string not in a correct format?

hi i need some help... i keep getting this error " Conversion from string not in correct format"
 is there something wrong with my coding? thanks for all help in advance
 
Dim a As Integer
        a = Int32.Parse(Label1.Text)

        Dim sqlStr As String = " SELECT * from Topic where [forumID] = '" + a + "' "

...