使用DataGridView更新数据时出错Update 无法找到 TableMapping['Table'] 或 DataTable“Table”。
为什么会这样，求大神帮忙
Public Class Form1
    Dim connstr As String = "Data Source=pc-20140831ptoa;Initial Catalog=student;Integrated Security=True"
    Dim conn As New SqlConnection(connstr)
    Dim da3 As SqlDataAdapter
    Dim ds3 As DataSet
    Public cb As SqlCommandBuilder       '定义为全局变量

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Dim sql2 = "select* from 课程权重 where 教师编号=1001 "
        Dim cmd2 As New SqlCommand(sql2, conn)
 da3 = New SqlDataAdapter(sql2, conn)
        ds3 = New DataSet()
        da3.Fill(ds3, "课程权重")

        DataGridView1.DataSource = ds3.Tables("课程权重")
End Sub
 Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
 'Try
        If ds3.HasChanges Then
           
            da3.Update(ds3.GetChanges)
           
            DataGridView1.CurrentCell = DataGridView1.Rows(0).Cells(0)
            MessageBox.Show("修改成功！")
        Else
            DataGridView1.CurrentCell = DataGridView1.Rows(0).Cells(0)
            MessageBox.Show("无修改的内容！")
        End If
        ' Catch ex As Exception
        '  MessageBox.Show("修改出错！")
        ' End Try
    End Sub
为什么会说找不到数据表呢，我是定义的全局啊，为什么就没有传过来，急啊！求大神帮忙

要疯了一直找不到原因，第一次用写，还多都不懂求大神帮忙啊