CREATE TABLE Kisi
(
	id int, 
	AdSoyad varchar(20),
	DogumTarihi date
)

<asp:GridView ID="GridView1" runat="server" OnRowDataBound="OnRowDataBound">
</asp:GridView>

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.BindGrid();
    }
}
 
private void BindGrid()
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        string query = "SELECT id, AdSoyad, DogumTarihi FROM Kisi";
        using (SqlCommand cmd = new SqlCommand(query))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    GridView1.DataSource = dt;
                    GridView1.DataBind();
                }
            }
        }
    }
}


protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        e.Row.Cells[2].Text = Convert.ToDateTime(e.Row.Cells[2].Text).ToString("dd, MMM yyyy");
    }
}