i can'n perform record update using RowUpdating in gridview?

Question

 

my code like there

 

and also file are atteched with db script and table code:

Please Any One Can Help Me.... 

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protected void gridStud_RowUpdating(object sender, GridViewUpdateEventArgs e)

{

LinkButton btn = (LinkButton)gridStud.Rows[e.RowIndex].FindControl("linkUpdate");

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", bal.studentId);

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

if (rd1.Checked)

{

cmd.Parameters.AddWithValue(bal.gender, "Male");

}

else

{

cmd.Parameters.AddWithValue(bal.gender, "Female");

}

cmd.Parameters.AddWithValue("brithDate", bal.brithDate);

cmd.Parameters.AddWithValue("emailid", bal.emailid);

cmd.Parameters.AddWithValue("mobilenumber", bal.mobilenumber);

c.ExecuteNonQueryByCommand(cmd);

gridStud.EditIndex = -1;

binddata();

}