主题：如何只更新符合要求的行内容

表B的DataColChanged

If e.DataCol.Name = "电话号码" Then
    Dim dr As DataRow = DataTables("表A").Find("车号 = '" & e.DataRow("车号") & "' And 电话号码 Is Null")
    If dr IsNot Nothing Then
        dr("电话号码") = e.DataRow("电话号码")
    End If
End If

按钮代码：

For Each r As Row In Tables("表A").Rows
    For Each r1 As Row In Tables("表B").Rows
        If r("车号") = r1("车号") AndAlso r("电话号码") = "" Then
            r("电话号码")  = r1("电话号码")
        End If
    Next
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