Consulta con un Gridview

' Gambas class file
PUBLIC rs AS Result
PRIVATE SUB updateFieldValue(filtro AS String)
DIM intRow AS Integer = 0
DIM strType AS String = ""
IF (NOT MDB.Connect()) THEN ME.Close()
rs = MDB.cn.Exec("SELECT * FROM alumno" & filtro)
IF rs.Available THEN
rs.MoveFirst
GridAlumnos.Columns.Count = 7
GridAlumnos.Rows.Count = rs.Count
FOR EACH rs
GridAlumnos[intRow, 0].Text = rs!No_control
GridAlumnos[intRow, 1].Text = rs!Nombre
GridAlumnos[intRow, 2].Text = rs!Apellidos
GridAlumnos[intRow, 3].Text = rs!Grado
GridAlumnos[intRow, 4].Text = rs!Grupo
GridAlumnos[intRow, 5].Text = rs!Direccion
GridAlumnos[intRow, 6].Text = rs!Telefono
INC intRow
NEXT
GridAlumnos.Row = intRow - 1
ENDIF
CATCH
Message.Error(Error.Class.Name & ": " & Error.Where & ": " & Error.Text)
END

PUBLIC SUB Form_Open()
updateFieldValue("")
END

'Boton de buscar
PUBLIC SUB ToolButton1_Click()
updateFieldValue(" WHERE No_control = '" & TextBox1.Text & "'")

END

'Boton mostrar todos los registros
PUBLIC SUB Button1_Click()
updateFieldValue("")
END