I use Sample II:

public DataTable ToDataTable(System.Data.Linq.DataContext ctx, object query)
{
     if (query == null)
     {
          throw new ArgumentNullException("query");
     }

     IDbCommand cmd = ctx.GetCommand(query as IQueryable);
     SqlDataAdapter adapter = new SqlDataAdapter();
     adapter.SelectCommand = (SqlCommand)cmd;
     DataTable dt = new DataTable("sd");

     try
     {
          cmd.Connection.Open();
          adapter.FillSchema(dt, SchemaType.Source); 
          adapter.Fill(dt);
     }
     finally
     {
          cmd.Connection.Close();
     }
     return dt;
}

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