How to add column in datagridview ( C# )

I have a code :

public DataTable Select_Category()
        {
            dt_category = ds.GetTable("SELECT * FROM itc_category");
            DataTable ndt = new DataTable();
            ndt.Columns.Add("id");
            ndt.Columns.Add("Cat Name");

            for (int i = 0; i < dt_category.Rows.Count; ++i)
            {
                ndt.Rows.Add(new object[] {
                   (i+1).ToString(),
                   dt_category.Rows[i]["cat_name"].ToString()
               });
            }
            return ndt;
        }

Code (markup):

with result below:
I have two columns
id and Cat Name

but I would like have 4 columns as shown below
id , Cat Name , Select , ComboBox

how to write code for two columns ?
Select ( checkbox ) and ComboBox

Please reply me solution.
thanks

 

Easy

public DataTable Select_Category()
        {
            dt_category = ds.GetTable("SELECT * FROM itc_category");
            DataTable ndt = new DataTable();
            ndt.Columns.Add("id");
            ndt.Columns.Add("Cat Name");
             ndt.Columns.Add("Select");
            ndt.Columns.Add("ComboBox");
            for (int i = 0; i < dt_category.Rows.Count; ++i)
            {
                ndt.Rows.Add(new object[] {
                   (i+1).ToString(),
                   dt_category.Rows[i]["cat_name"].ToString(),.....
               });
            }
            return ndt;
        }

Code (markup):

 

Thats the right answer.
Thanks echipvina.