Protected Sub ddlnik_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ddlnik.SelectedIndexChanged
        Call konek_sql_server()
        cmd_sql_server = New SqlCommand("select siswa.nik,siswa.nama,siswa.fakultas,siswa.jurusan,nilai.nilai1,nilai.nilai2,nilai.nilai3 from siswa inner join nilai on nilai.nik =siswa.nik where siswa.nik like @nik + '%'", conn_sql_server)
        cmd_sql_server.Parameters.AddWithValue("@nik", ddlnik.SelectedItem)
        da_sql_server = New SqlDataAdapter(cmd_sql_server)
        dt = New DataTable()
        da_sql_server.Fill(dt)
        gv_siswa.DataSource = dt
        gv_siswa.DataBind()

    End Sub

When I select the Items Nothing Happened To Gridview..

Anyone can help me?...