Editable Unbound Gridview in ASP.Net

private System.Data.DataTable Populate_GridView()
  {
      string qry = "SELECT     tbl_Emp_Master.Emp_ID, tbl_Emp_Master.Emp_Name, tbl_Emp_Master.Login_ID,  tbl_Emp_Master.BU_Code, tbl_Emp_Master.DM_Code, " +
                          " tbl_Emp_Master.Emp_Role, tbl_Emp_Role.[Role_Desc], tbl_BU.BU_Name, tbl_DM.DM_Name " +
                      " FROM         tbl_DM INNER JOIN " +
                          " tbl_BU ON tbl_DM.BU_Code = tbl_BU.BU_Code INNER JOIN " +
                          " tbl_Emp_Master INNER JOIN " +
                          " tbl_Emp_Role ON tbl_Emp_Master.Emp_Role = tbl_Emp_Role.Emp_Role ON tbl_DM.DM_Code = tbl_Emp_Master.DM_Code AND  " +
                          " tbl_BU.BU_Code = tbl_Emp_Master.BU_Code";
      SqlCon.Open();
      SqlDataAdapter adp = new SqlDataAdapter(qry, SqlCon);
      System.Data.DataTable dt = new System.Data.DataTable();
      System.Data.DataRow dr = dt.NewRow();
      dt.Rows.InsertAt(dr, 0);
      adp.Fill(dt);
      SqlCon.Close();
      return dt;
  }
  private void View_Table()
  {
      System.Data.DataTable dt = Populate_GridView();
      GridView1.DataSource = dt;
      GridView1.EditIndex = -1;
      GridView1.DataBind();
      ((LinkButton)GridView1.Rows[0].Cells[0].Controls[0]).Text = "Insert";
  }

  protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
  {
      SqlCommand cmd = new SqlCommand();
      cmd.CommandText = "UPDATE tbl_Emp_Master SET Emp_ID= '" + e.NewValues[0].ToString() + "', Emp_Name ='" + e.NewValues[1].ToString() + "', Login_ID='" + e.NewValues[2].ToString() + "', BU_Code='" + e.NewValues[3].ToString() + "', DM_Code='" + e.NewValues[4].ToString() + "', Emp_Role='" + e.NewValues[5].ToString() + "' " +
                       "WHERE  Emp_ID= '" + e.NewValues[0].ToString() + "'";
      cmd.Connection = SqlCon;
      SqlCon.Open();
      cmd.ExecuteNonQuery();
      SqlCon.Close();
      View_Table();

  }
  protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
  {
      System.Data.DataTable dt = Populate_GridView();
      GridView1.DataSource = dt;
      GridView1.EditIndex = e.NewEditIndex; //Enable Edit Mode for Selected Row
      GridView1.DataBind();
      ((LinkButton)GridView1.Rows[0].Cells[0].Controls[0]).Text = "Insert";
  }
  protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
  {
      View_Table();
  }