How to edit or delete database record using grid view?

Description:
Grid view operation is easy to edit the data but i saw in the forum section some of the .Net Beginner struggle to Update or delete values using grid view operation. we update or delete record detail in the database using grid view data key values.

How to Update record using Grid view?
We have stored lots of record in the table and each record identified with help of primary key field. Here is the same logic applied we update each record based on the primary key value of that selected record. we have set primary key field of table as Gridview Data Key Name. After user click edit link and enter values click update button this time we update values of the selected record using Grid View Data Key value in the RowUpdating event.

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {

        GridViewRow row = GridView1.Rows[e.RowIndex];
        string eno;

        eno = GridView1.DataKeys[e.RowIndex].Value.ToString();

        TextBox empname = (TextBox)row.FindControl("txtempname");
        TextBox sal = (TextBox)row.FindControl("txtsal");

        sqlcon.Open();
        sqlcmd = new SqlCommand("update emp set empname='" + empname.Text +"',sal='" + sal.Text +"' where eno='" + eno + "'" , sqlcon);
        sqlcmd.CommandType = CommandType.Text;        
        sqlcmd.ExecuteNonQuery();
        sqlcon.Close();
        GridView1.EditIndex = -1;
        GridData();
    }

protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        String eno;
        eno = GridView1.DataKeys[e.RowIndex].Value.ToString();
        sqlcmd = new SqlCommand("delete from emp where eno='" + eno +"'", sqlcon);
        sqlcon.Open();
        sqlcmd.CommandType = CommandType.Text;        
        sqlcmd.ExecuteNonQuery();
        sqlcon.Close();
        GridData();		//Common method for refresh grid
    }

GridView1.PageIndex = e.NewPageIndex;
// GridData() is a Common method for refresh grid check attached source code
GridData();