i can'n perform edit and delete operation?

Question

code like this

using System;
using System.Web.UI.HtmlControls;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using GridFun.BE;
using GridFun.DAL;
using GridFun.Common;
using System.Data.SqlClient;
using System.Data;

public partial class Student : System.Web.UI.Page
{

    studentDAL dal = new studentDAL();
    studentBE bal= new studentBE();

    protected void Page_Load(object sender, EventArgs e)
    {

        if (!IsPostBack)
        {
            //bal = new studentBE();
            //dal = new studentDAL();
            //gridStud.DataSource = dal.getdata();
            //gridStud.DataBind();
            binddata();
        }
    }

    public void binddata()
    {
        gridStud.DataSource = dal.getdata();
        gridStud.DataBind();
    }

    protected void BtnAdd_Click(object sender, EventArgs e)
    {
        dal = new studentDAL();
        bal = new studentBE();
        bal.name = txtStudentName.Text;
        if (RadioButton1.Checked)
        {
            bal.gender = "Male";
        }
        else
        {
            bal.gender = "Female";
        }
        bal.brithDate = Convert.ToDateTime(TextCalendar.Text);
        bal.emailid = txtEmail.Text;
        bal.mobilenumber = txtMobile.Text;
        bal.status = 1;
        bal.createdOn = DateTime.Now;
        bal.modifiedOn = DateTime.Now;
        dal.addStudent(bal);
        Response.Redirect("Student.aspx");
    }


    protected void gridStud_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        LinkButton btn = (LinkButton)gridStud.Rows[e.RowIndex].FindControl("linkUpdate");

        if (btn.CommandName == "UPDATE")
        {
            int studentId = Convert.ToInt32(gridStud.DataKeys[e.RowIndex].Value.ToString());

            TextBox txtStudName = (TextBox)gridStud.Rows[e.RowIndex].FindControl("txtStud");
            RadioButton rd1 = (RadioButton)gridStud.Rows[e.RowIndex].FindControl("RadioButton3");
            RadioButton rd2 = (RadioButton)gridStud.Rows[e.RowIndex].FindControl("RadioButton4");

            TextBox txtBirthdate = (TextBox)gridStud.Rows[e.RowIndex].FindControl("txtDate");
            TextBox txtEmail = (TextBox)gridStud.Rows[e.RowIndex].FindControl("txtEmail");
            TextBox txtMobile = (TextBox)gridStud.Rows[e.RowIndex].FindControl("txtmob");




                    studentCommon c = new studentCommon();
                    SqlCommand cmd = new SqlCommand("studIUD");
                    cmd.CommandType = CommandType.StoredProcedure;

                    cmd.Parameters.AddWithValue("StatementType", "UPDATE");

                    // cmd.Parameters.AddWithValue("studentId", studentId);

                    cmd.Parameters.AddWithValue("name", txtStudName);

                    if (rd1.Checked)
                    {
                        cmd.Parameters.AddWithValue("gender", "Male");
                    }
                    else {
                        cmd.Parameters.AddWithValue("gender", "Female");
                    }




                    cmd.Parameters.AddWithValue("brithDate", txtBirthdate);
                    cmd.Parameters.AddWithValue("emailid", txtEmail);
                    cmd.Parameters.AddWithValue("mobilenumber", txtMobile);

                    c.ExecuteNonQueryByCommand(cmd);
               gridStud.EditIndex = -1;
               gridStud.DataBind();
        }
    }
    protected void gridStud_RowEditing(object sender, GridViewEditEventArgs e)
    {
        gridStud.EditIndex = e.NewEditIndex;
        //gridStud.DataBind();
        binddata();
    }
    protected void gridStud_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        gridStud.PageIndex = e.NewPageIndex;
        gridStud.DataBind();
    }
    protected void gridStud_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        studentDAL stuDal = new studentDAL();

            int studid = Convert.ToInt32(gridStud.DataKeys[e.RowIndex].Values["studentId"].ToString());
            stuDal.deleteStudent(studid);

    }

    protected void gridStud_RowDataBound(object sender, GridViewRowEventArgs e)
    {

        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            try
            {

                HiddenField hidenGender = (e.Row.FindControl("HiddenGender") as HiddenField);
                if (hidenGender.Value != "")
                {

                    RadioButton rb1 = (RadioButton)e.Row.Cells[0].FindControl("RadioButton3");
                    RadioButton rb2 = (RadioButton)e.Row.Cells[0].FindControl("RadioButton4");
                    if (rb1 != null && rb2 != null)
                    {
                        if (hidenGender.Value == "Male")
                        {
                            rb1.Checked = true;
                        }
                        else
                        {
                            rb2.Checked = true;
                        }
                    }


                }

            }
            catch (Exception ex)
            {

                throw;
            }

        }
    }
}