主题：求教:判断某列相同编号的最大值

 如此代码，测试有效，自己修改。

Dim ls As New List(Of String)
For Each dr As DataRow In DataTables("表A").DataRows
    Dim name As String = dr("第一列").substring(0, dr("第一列").indexof("-"))
    If ls.Contains(name) = False Then
        ls.Add(name)
        Dim fdr As DataRow = DataTables("表A").Find("第一列 like '" & name & "-*'", "第一列 desc")
        fdr("第二列") = "有效"
    End If
Next

Dim ls As New List(Of String)
Dim idx As New List(Of Integer)
For Each dr As DataRow In DataTables("表A").DataRows
    Dim name As String = dr("第一列").substring(0, dr("第一列").indexof("-"))
    If ls.Contains(name) = False Then
        ls.Add(name)
        Dim fdr As DataRow = DataTables("表A").Find("第一列 like '" & name & "-*'", "第一列 desc")
        idx.Add(fdr("_Identify"))       
        fdr("第二列") = "有效"
    Else If idx.Contains(dr("_Identify")) = False Then
        dr("第二列") = "无效"
    End If
Next

 恩恩确实是写错了，没有注意之后的情况。已经修改。

 还有更好的方便，不过，够用就好了。

呵呵，确实，这次可以了。

Dim ls As New List(Of String)
Dim idx As New List(Of Integer)
For Each dr As DataRow In DataTables("表A").DataRows
    Dim name As String = dr("第一列").substring(0, dr("第一列").indexof("-"))
    If ls.Contains(name) = False Then
        ls.Add(name)
        Dim fdr As DataRow = DataTables("表A").Find("第一列 like '" & name & "-*'", "第一列 desc")
        idx.Add(fdr("_Identify"))      
        dr("第二列") = "无效"
        fdr("第二列") = "有效"
    Else If idx.Contains(dr("_Identify")) = False Then
        dr("第二列") = "无效"
    End If
Next

 再精简一下代码就这样。

Dim prev As String = "-"
For Each dr As DataRow In DataTables("表A").Select("", "第一列 desc")
    If dr("第一列") Like prev.SubString(0, prev.IndexOf("-")) & "-*" = False Then
        dr("第二列") = "有效"
        prev = dr("第一列")
    Else
        dr("第二列") = "无效"
    End If
Next