How to create a dynamic LINQ join extension method

Question

There was a library of dynamic LINQ extensions methods released as a sample with Visual Studio 2008. I\'d like to extend it with a join method. The code below fail

Answer 1

Here is some sample code showing a join on multiple columns. Using a datatable and datarows you need to always access fields via the indexer.

  DataTable t1 = new DataTable();
  t1.Columns.Add("FundId", typeof(int));
  t1.Columns.Add("Date", typeof(DateTime));
  t1.Columns.Add("CodeA", typeof(string));
  t1.Rows.Add(1, new DateTime(2010, 01, 01), "A1");
  t1.Rows.Add(2, new DateTime(2010, 01, 01), "A2");
  t1.Rows.Add(3, new DateTime(2010, 01, 01), "A3");

  DataTable t2 = new DataTable();
  t2.Columns.Add("FundId", typeof(int));
  t2.Columns.Add("Date", typeof(DateTime));
  t2.Columns.Add("CodeB", typeof(string));
  t2.Rows.Add(1, new DateTime(2010, 01, 01), "B1");
  t2.Rows.Add(2, new DateTime(2010, 01, 01), "B2");
  t2.Rows.Add(3, new DateTime(2010, 01, 01), "B3");

  IQueryable outerTable = t1.AsEnumerable().AsQueryable();
  IEnumerable innerTable = t2.AsEnumerable();

  var query = outerTable.Join
    (
      innerTable, 
      "new(get_Item(0) as FundId, get_Item(1) as Date)",
      "new(get_Item(0) as FundId, get_Item(1) as Date)",
      "new(outer.get_Item(0) as FundId, outer.get_Item(2) as CodeA, inner.get_Item(2) as CodeB)"
    );