LINQ to DataTable，查找重复的行 [英] LINQ to DataTable, finding duplicate rows

问题描述

使用以下DataTable：

Using the following DataTable:

    Dim d As New DataTable()
    d.Columns.Add("Product", GetType(System.String))
    d.Columns.Add("Value", GetType(System.Double))

    d.Rows.Add(New Object() {"OAP1", 100.0})
    d.Rows.Add(New Object() {"EPP4", 100})
    d.Rows.Add(New Object() {"OAP1", 150.25})
    d.Rows.Add(New Object() {"OAPIN", 200.0})

我试图使用LINQ来确定是否有不止一种任何类型的产品。在SQL中，这可以像下面这样工作：

I'm trying to use LINQ to identify if there are more than one of any type of product. In SQL, this would work something like:

SELECT Product FROM SOME_TABLE HAVING COUNT(*) > 1

我不能为我的生活在LINQ中如何做到这一点。我正在跟随一个这样做的人：

I can't for the life of me work out how to do this in LINQ. I was following someone who did something like this:

    Dim q = From row In d.AsEnumerable()
            Group row By New { column1 = row("Product"), column2 = row("Value") }
            Into grp
            Where grp.Count() > 1
            Select row

    For Each item In q
        ' 'q' is not declared. It may be inaccessible due to its protection level.
    Next

但是当我尝试使用q时，我收到错误。任何关于我如何使这项工作的想法？

But I get an error when I try to actually use 'q'. Any ideas on how I can make this work?

推荐答案

尝试这个

Dim duplicates = d.AsEnumerable().GroupBy(Function(i) i.Field(Of String)("Product")).Where(Function(g) g.Count() > 1).Select(Function(g) g.Key)

For Each dup In duplicates
Next

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