How Can I Add Dynamically More Than One Columns Into The Gridview

public void load_dynamic_grid()
      {
          try
          {
               DataTable dt = new DataTable();
               string name = txtnm.Text;
      DataColumn dcol = new DataColumn(name, typeof(System.String));
      dt.Columns.Add(dcol);


          DataRow drow = dt.NewRow();


          drow[name] = "Rows" ;


          dt.Rows.Add(drow);


      foreach (DataColumn col in dt.Columns)
      {
          //Declare the bound field and allocate memory for the bound field.
          BoundField bfield = new BoundField();

          //Initalize the DataField value.
          bfield.DataField = col.ColumnName;

          //Initialize the HeaderText field value.
          bfield.HeaderText = col.ColumnName;

          //Add the newly created bound field to the GridView.
          gvAlumni.Columns.Add(bfield);
      }

      //Initialize the DataSource
      gvAlumni.DataSource = dt;

      //Bind the datatable with the GridView.
      gvAlumni.DataBind();
          }
          catch (Exception ex)
          {
              throw (ex);
          }

      }

      protected void btnSave_Click(object sender, EventArgs e)
      {
          load_dynamic_grid();
          txtnm.Text = "";
      }