using datatable how to add column name maually

<asp:gridview id="GridView1" runat="server" autogeneratecolumns="false" onrowdatabound="GridView1_RowDataBound" xmlns:asp="#unknown">
     <columns>
          <asp:templatefield headertext="Course">
               <itemtemplate>
               DO Something!
               </itemtemplate>
          </asp:templatefield>
     </columns>
     <columns>
          <asp:templatefield headertext="Batchid">
               <itemtemplate>
               DO Something!
               </itemtemplate>
          </asp:templatefield>
     </columns>
     <columns>
          <asp:templatefield headertext="Rate">
               <itemtemplate>
               DO Something!
               </itemtemplate>
          </asp:templatefield>
     </columns>
</asp:gridview>

DataTable Dt = new DataTable();
DataColumn Dc = new DataColumn("Course");
DataColumn Dc1 = new DataColumn("Batchid");
DataColumn Dc2 = new DataColumn("Rate");
Dt.Columns.Add(Dc);
Dt.Columns.Add(Dc1);
Dt.Columns.Add(Dc2);

DataRow dr = Dt.NewRow();
dr["Course"] = "MCA";
dr["Batchid"] = "111";
dr["Rate"] = "A";
Dt.AcceptChanges();

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;


namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            DataTable dt = new DataTable("mydatatable");
            DataColumn dc = new DataColumn("TextColumn", Type.GetType("System.String"));
            dt.Columns.Add(dc);
            dc = new DataColumn("IntegerColumn", Type.GetType("System.Int32"));
            dt.Columns.Add(dc);
            dc = new DataColumn("DecimalColumn", Type.GetType("System.Decimal"));
            dt.Columns.Add(dc);

            foreach (DataColumn c in dt.Columns)
            { 
                Console.WriteLine(c.ColumnName.ToString());
            }
            Console.ReadKey();
        }
    }
}

DataTable table = new DataTable();
table.Columns.Add("Name", typeof(int));
table.Columns.Add("Age", typeof(string));