出现对象‘Refresh’的方法‘IAdadc错误’，怎么才能解决？

Private Sub cmdFind_Click()     '查询
    Dim strSQL, sTmp As String
    Dim strSno, sSno As String
    Dim strSname, sSname As String
    Dim strSClass, sSclass As String
    strSno = Trim(txtSno.Text)
    strSname = Trim(txtSname.Text)
    strSname = Trim(txtClass.Text)
    strSQL = "select Sno,Sname,Sdept,Sclass,Cno,Cname,Grade from V_StudentCourseGrade"
    sSno = ""
    If ckbSno.Value = 1 Then
        sSno = " Sno = '" + strSno + "'"
    End If
    sSname = ""
    If ckbSname.Value = 1 Then
        sSname = " Sname like '% " + strSname + " % '"
    End If
    If ckbClass.Value = 1 Then
        sSclass = " S.Sclass = '" + strClass + "'"
    End If
    sTmp = ""
    If sSno <> "" Then
        If sSname <> "" Then
            sTmp = sSno + " and " + sSname
            If sSclass <> "" Then
                sTmp = sTmp + "and" + sSclass
            End If
        Else
            If sSclass <> "" Then
                sTmp = sSno + "and" + sSclass
            Else
                sTmp = sSno
            End If
        End If
    Else
        If sSname <> "" Then
            If sSclass <> "" Then
                sTmp = sSname + "and" + sSclass
            Else
                sTmp = sSname
            End If
        Else
            sTmp = sSclass
        End If
    End If
        If Trim(sTmp) <> "" Then
        strSQL = strSQL + "where" + sTmp
        End If
        gradeADO.ConnectionString = getConnString
        gradeADO.RecordSource = strSQL
        gradeADO.Refresh
End Sub