using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace System.Web.UI.WebControls
{
    public static class Methods
    {
        public static void RenderConfiguration(this GridView grid)
        {
            grid.GridLines = GridLines.Both;
            grid.CellPadding = 5;
            grid.CellSpacing = 6;
            grid.Width = new Unit("100%");
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace WebApplicationForms
{
    public partial class About : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                GridView1.RenderConfiguration(); // chamando configuração padrão!
                GridView1.DataSource = new object[]{
                    new {Id = 1, Nome = "GridView 1"},
                    new {Id = 2, Nome = "GridView 2"},
                    new {Id = 3, Nome = "GridView 3"},
                    new {Id = 4, Nome = "GridView 4"},
                    new {Id = 5, Nome = "GridView 5"}
                };
                GridView1.DataBind();
            }
        }
    }
}