Return LINQ query to DataTable .NET 3.5?

问题

I want to query two DataTables (populated by parsing Excel files) using LINQ and join them on a matching field, "UPC", as follows:

Dim query = From c In dt.AsEnumerable() _
Join r In dtUnits.AsEnumerable() _
On c.Field(Of String)("UPC") Equals r.Field(Of String)("UPC") _
Select New With {.UPC = r.Field(Of String)("UPC")}

Additionally, I want to copy this LINQ query result to a DataTable. I found a method CopyToDataTable(), but it is in .NET 4.5, and our server only supports .NET 3.5.

What can I do to emulate this functionality in VB .NET 3.5?

Thank you!

回答1:

CopyToDataTable is already there since .NET 35. But the problem is that you want to create a DataTable "from the scratch" from an anonymous type. That doesn't work.

CopyToDataTable is an extension for IEnumerable<DataRow> only. So you either have to select one DataRow from your joined DataTables:

Dim query = From c In dt.AsEnumerable() _
            Join r In dtUnits.AsEnumerable() _
            On c.Field(Of String)("UPC") Equals r.Field(Of String)("UPC") _
            Select c
Dim table = query.CopyToDataTable()

or use this ObjectShredder which uses reflection, hence is not the most efficient way(C# implementation).

回答2:

Take a look at this article:

http://codecorner.galanter.net/2009/12/17/grouping-ado-net-datatable-using-linq/

You can use .toDataTable method, but only if your LINQ Query returns actual DataTable rows. For a custom type you can use attached to the article code to perform the same.