主题：填充代码

Dim Fjs As List(Of String) = DataTables("表A").GetUniqueValues("", "房间号")
For Each Fj As String In Fjs
    Dim dr1 As DataRow = DataTables("表A").Find("房间号 = '" & Fj & "'","_Identify Desc")
    Dim dr2 As DataRow = DataTables("表A").AddNew()
    dr2("年月") = e.Form.Controls("TextBox1").Value
    dr2("房间号") = Fj
    dr2("上月读数") = dr1("本月读数")
Next

出错的原因留着你自己找，解决办法好好想想。

没想出办法？

改这句：

Dim Fjs As List(Of String) = DataTables("表A").GetUniqueValues("房间号 Is Not Null", "房间号")

自己做个判断呀。

Dim Exergue As String = e.Form.Controls("TextBox1").Value
Dim r As DataRow = DataTables("表A").Find("年月 = '" & Exergue & "'")
If r IsNot Nothing Then
    MessageBox.Show("表中已存在 " & Exergue,"提示",MessageBoxButtons.Ok,MessageBoxIcon.Information)
    Return
End If
Dim Fjs As List(Of String) = DataTables("表A").GetUniqueValues("房间号 Is Not Null", "房间号")
For Each Fj As String In Fjs
    Dim dr1 As DataRow = DataTables("表A").Find("房间号 = '" & Fj & "'","_Identify Desc")
    Dim dr2 As DataRow = DataTables("表A").AddNew()
    dr2("年月") = Exergue
    dr2("房间号") = Fj
    dr2("上月读数") = dr1("本月读数")
Next