主题：请求指点，代码优化

原代码：

CurrentTable.DataTable.DataCols.Add("存在",Gettype(String),255)
For Each dr1 As DataRow In CurrentTable.DataTable.DataRows
    Dim dr2 As DataRow = DataTables("hushu").Find("NSRSBH =  '" & dr1("NSRSBH") & "'")
    If dr2 IsNot Nothing Then
        dr1("存在") = dr2("NSRMC")
    End If
Next

自己优化后代码：

CurrentTable.DataTable.DataCols.Add("存在",Gettype(String),255)
Dim lst1 As New List(of DataRow)
For Each dr1 As DataRow In CurrentTable.DataTable.DataRows
    Dim dr2 As DataRow = DataTables("hushu").Find("NSRSBH =  '" & dr1("NSRSBH") & "'")
    If dr2 IsNot Nothing Then
        'dr1("存在") = dr2("NSRMC")
        lst1.Add(dr2)
    End If
Next
For Each dr1 As DataRow In CurrentTable.DataTable.DataRows
    For Each dr As DataRow In lst1
        dr1("存在") = dr("NSRMC")
    Next
Next

优化前17万行数据运行102秒，优化后基本无法运行。请求指点！