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我很难加入 2 个数据表，结果是加入了数据表。

第一个数据表（标签）保存包括打印机标识的数据。第二个数据表（打印机）保存打印机引用（id > unc）

我想拥有一个数据表作为最终结果（加入），其中包含来自第一个数据表的所有数据以及第二个数据表的字段（unc）。

这就是我一直在尝试的：（注意固定路径是为了方便......）

Sub Main()

    Dim ds1 As new DataSet

    ds1.ReadXml("C:\Program Files (x86)\[COMPANY]\ASW2XML\BICOLOR_a07bfc62-501e-4444-9b6e-3b9d3550e1a4.xml")

    Dim ds2 As New DataSet

    Dim li As string()

    li = IO.File.ReadAllLines("C:\Program Files (x86)\[COMPANY]\ASW2XML\printers.dat")

    Dim printers As New DataTable("Printers")

    printers.Columns.Add("REPRT2")
    printers.Columns.Add("REPRT3")

    For Each s In li.ToList

        Dim dr As DataRow = printers.NewRow

        dr.Item(0) = s.Split("=")(0)
        dr.Item(1) = s.Split("=")(1)

        printers.Rows.Add(dr)

    Next

    printers.AcceptChanges

    Dim labels As DataTable = ds1.Tables(0)

    Dim joined As new DataTable("data")

        'Dim lnq = From label In labels.AsEnumerable Join printer In printers.AsEnumerable On label("REPRT") Equals printer("REPRT2") Select printer
        'Dim lnq = From l In labels Group Join p In printers On l Equals p("REPRT2") Into Group From p In Group Select label = l, ppath = If(p Is Nothing, "(Nothing)", p("REPRT3"))
        Dim lnq = labels.AsEnumerable().Where(Function(o)printers.Select("REPRT2 =" & o.Item("REPRT").ToString).Length = 0)

        joined = lnq.CopyToDataTable


End Sub

感谢您的帮助和启发！

grtz -S-

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3 回答 3

1

你试过http://msdn.microsoft.com/en-us/library/system.linq.enumerable.join.aspx

将您的数据表作为 IEnumerable 的扩展（就像您所做的那样使用 list ），并且加入 linq 可以使其轻松工作。

然后将连接的表发送到您想要的任何目的地。

于 2012-06-01T20:48:10.203 回答
1

我认为评论会更难理解，所以我把它移到了一个帖子中。

我写了一些结构来帮助你理解 Join 的工作原理：

structure Label
    Public printerId as long
    Public driver as Strring
end structure

structure Printer
    Public unc as string
end structure

如果您将标签和打印机设置为 DataTable（而不是下面的结构），您应该有类似的内容：

 function DoJoin() as datatable 
    'You might remove as datatable in query declaration
    dim query as datatable = Labels.Join(Printers, Function(aLabel) aLabel, _
    function(aPrinter) aPrinter.unc, _
    function(aLabel, aPrinter) New With  
    { .printerID = aLabel.printerId, .driver = aLabel.Driver, _
      .unc = aPrinter.unc
    })
    return query 
end function

However I wote it this morning in notepad, so you might have to adjust this. I just want to add that you must have the same type of container in order to use join (eg : example in Join at msdn they used 2 Lists.), that are compatible with Linq obects (datatable I do not know).

于 2012-06-04T14:43:37.400 回答
0

我决定以“硬”的方式来做，并遍历父表中的所有行。这对于少量记录来说非常快，我不知道在大量记录上运行它是否会大大降低使用 Linq 解决方案的速度......

这是我正在使用 atm 的代码：

Sub Main()

    Dim ds As new DataSet

    ds.ReadXml("C:\Program Files (x86)\[COMPANY]\ASW2XML\BICOLOR_a07bfc62-501e-4444-9b6e-3b9d3550e1a4.xml")

    Dim labels As DataTable = ds.Tables(0)
    Dim printers As DataTable = GetPrinters

    labels.Columns.Add("REPRT2").SetOrdinal(labels.Columns.IndexOf("REPRT")+1) 'insert new column after key column
    labels.CaseSensitive=False
    labels.AcceptChanges

    For Each dr As DataRow In labels.Rows

        Dim p As String = String.Empty

        Try
            p = printers.Select("ID='" & dr("REPRT") & "'")(0).Item("PATH").ToString
        Catch ex As Exception

        End Try

        dr("REPRT2") = p

    Next

    labels.AcceptChanges

End Sub

Function GetPrinters As DataTable

    Dim printers As New DataTable("Printers")

    Dim li As string()

    li = IO.File.ReadAllLines("C:\Program Files (x86)\[COMPANY]\ASW2XML\printers.dat")

    printers.Columns.Add("ID")
    printers.Columns.Add("PATH")

    For Each s In li.ToList

        Dim dr As DataRow = printers.NewRow

        dr.Item(0) = s.Split("=")(0)
        dr.Item(1) = s.Split("=")(1)

        printers.Rows.Add(dr)

    Next

    printers.AcceptChanges

    Return printers

End Function
于 2012-06-02T09:34:26.427 回答