vb.net 至少一个参数没有被指定值

Question

       Dim Name_CN As String = Name_CN_TextBox.Text  

Dim Personal_guid

    Personal_guid = Message_Oprations.DataGridView1.CurrentRow.Cells(14).Value.ToString

    cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\todd.ge\Documents\Visual Studio 2010\Projects\9.16\WindowsApplication4\information.mdb;Persist Security Info=False")
    cn.Open()
    Dim sql4 As String = "update Personal_table set Name_CN = '" & Name_CN & "' where  Job_guid ='" & Personal_guid & "'"
    cm = New OleDbCommand(sql4, cn)
    cm.ExecuteNonQuery()
    cn.Close()
    cn.Open()

已经单个测试过，Name_CN和Personal_guid都有值