关于datacolumnchanging的使用

[amice]

我想在datacolumnchanging方法中添加校验的代码，但是该段代码并未执行，问什么呢？
Private Sub btnmodify_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnmodify.Click
Dim dtuser As DataTable = New DataTable("dbuserinfor")
AddHandler dtuser.ColumnChanging, AddressOf columnchangeing
Me.BindingContext(DataSet11, "dbuserinfor").EndCurrentEdit()
Dim sqlcmdbd As SqlClient.SqlCommandBuilder = New SqlClient.SqlCommandBuilder(sqldauser)
sqldauser.Update(DataSet11, "dbuserinfor")
DataSet11.DBUserInfor.AcceptChanges()
End Sub

Protected Sub columnchangeing(ByVal sender As System.Object, ByVal e As System.Data.DataColumnChangeEventArgs)
If e.ProposedValue Is Nothing Then
MsgBox("value is nothing")
End If
End Sub

[ruanyuping]

rt