PLINQ AsParallel错误与数据表

Question

I am trying to use AsParallel with the datatable

using System.Linq;


var row = from r0w1 in dt.AsEnumerable().AsParallel()
          join r0w2 in curdt.AsEnumerable().AsParallel()
          on r0w1.Field<string>("B") equals r0w2.Field<string>("cr_B")
          join r0w3 in tbmdt.AsEnumerable().AsParallel()
          on r0w1.Field<string>("B") equals r0w3.Field<string>("tb_B") into ps
          from r0w3 in ps.DefaultIfEmpty()
          select new string[] { serial_number++.ToString() }
          .Concat(r0w1.ItemArray.Concat
          (r0w2 != null ? r0w2.ItemArray.Skip(1) : new object[] { "", "", "", "" })
          .Concat(r0w3 != null ? r0w3.ItemArray.Skip(1) : new object[] { "", "", "", "" })).ToArray();

But I am getting an error here

system.data.enumerablerowcollection<system.data.datarow> does not contain a definition for 'Asparallel'

I am using visual studio 2008. Do I need any extra library for this ?

Answer 1

Bad idea to use AsParallel in inner statements. You won't speed up DB querying.

Put it in the end, if you need to operate collection:

var row = from r0w1 in dt
          join r0w2 in curdt
          on r0w1.Field<string>("B") equals r0w2.Field<string>("cr_B")
          join r0w3 in tbmdt.AsEnumerable().AsParallel()
          on r0w1.Field<string>("B") equals r0w3.Field<string>("tb_B") into ps
          from r0w3 in ps.DefaultIfEmpty()
          select new string[] { serial_number++.ToString() }
          .Concat(r0w1.ItemArray.Concat
          (r0w2 != null ? r0w2.ItemArray.Skip(1) : new object[] { "", "", "", "" })
          .Concat(r0w3 != null ? r0w3.ItemArray.Skip(1) : new object[] { "", "", "", "" })).AsParallel();

Answer 2

You can't use AsParallel (or any linq extension methods as far as I know) on the DataRow class. You can use it on DataTable though, and then just use DataTable.Rows .

Also using AsParallel won't really do anything in your case, only do it when you need to query on different elements of a collection simultaneously when order, or intermediate results aren't needed.