The GridView of ASP

Using System;
Using System.Collections.Generic;
Using System.Linq;
Using System.Web;
Using System.Web.UI;
Using System.Web.UI.WebControls;
Using System.Data;
Using DBHelper;

public partial class Student:System.Web.UI.Page
{
public string ID;
protected void Page_Load (object sender, EventArgs e)
{
if (! IsPostBack)
{
viewstate["SortOrder"] = "stu_id";
viewstate["Orderdire"] = "ASC";
Bind ();
}
}


protected void Gridview1_rowdeleting (object sender, Gridviewdeleteeventargs e)
{
String sqlstr = "Delete from t_student where stu_id= '" + gridview1.datakeys[e.rowindex]. Value.tostring () + "'";
Sqlhelper.exectenonquerytext (sqlstr, NULL);
Response.Write ("<script>alert (' Delete succeeded! ') </script> ");
Gridview1.editindex =-1;
Bind ();
}


protected void Gridview1_sorting (object sender, GridViewSortEventArgs e)
{
string spage = E.sortexpression;
if (viewstate["SortOrder"]. ToString () = = spage)
{
if (viewstate["Orderdire"]. ToString () = = "Desc")
{
viewstate["Orderdire"] = "ASC";
}
Else
{
viewstate["Orderdire"] = "Desc";
}
}
Else
{
viewstate["SortOrder"] = e.sortexpression;
}
Bind ();
}
protected void Gridview1_pageindexchanging (object sender, Gridviewpageeventargs e)
{
This. Gridview1.pageindex = E.newpageindex;
Bind ();
}

public void Bind ()
{
String sql = "SELECT * from T_student where 1=1";
DataTableCollection DC = sqlhelper.gettabletext (sql, NULL);
DataView view = dc[0]. DefaultView;
String sort = (string) viewstate["SortOrder"] + "" + (String) viewstate["Orderdire"];
View. sort = sort;
This. Gridview1.datasource = view;
Gridview1.datakeynames = new string[] {"stu_id"};//primary key
This. Gridview1.databind ();
}
protected void Button1_Click (object sender, EventArgs e)
{
Response.Write (ID);

}

protected void Checkbox1_checkedchanged (object sender, EventArgs e)
{
for (int i = 0; I <= gridview1.rows.count-1; i++)
{
CheckBox checkbox = (checkbox) Gridview1.rows[i]. FindControl ("CheckBox1");
if (checkbox.checked = = True)
{
Id=gridview1.rows[i]. Cells[0]. Text.tostring (). Trim ();
}
}
}
protected void button2_click (object sender, EventArgs e)
{
Response.Redirect ("student_detail.aspx?id=" +id);
}
protected void Button3_Click (object sender, EventArgs e)
{
Response.Redirect ("student_detail.aspx?stu_id=" + ID);
}
}

The GridView of ASP