Getting Error: object reference not set to an instance of an

public partial class update_admin_profile : System.Web.UI.Page

{

string s1 = ConfigurationManager.ConnectionStrings["db"].ToString();

protected void Page_Load(object sender, EventArgs e)

{

if (!Page.IsPostBack)

{

BindRepeater();

string s2 = Session["userid"].ToString();

}

}

private void BindRepeater()

{

string s2 = Session["userid"].ToString();

int i = Convert.ToInt32(s2);

SqlConnection SqlCnn = new SqlConnection(s1);

SqlCommand SqlCmd = new SqlCommand("select * from mla_registration where user_id='" + i + "'", SqlCnn);

SqlDataAdapter SqlAd1 = new SqlDataAdapter(SqlCmd);

DataSet ds = new DataSet();

SqlAd1.Fill(ds, "mla_registration");

repeater1.DataSource = ds;

repeater1.DataBind();

}

protected void RepterDetails3_ItemCommand(object source, RepeaterCommandEventArgs e)

{

LinkButton lnkUpdate = (LinkButton)e.Item.FindControl("lnkUpdate");

LinkButton lnkCancel = (LinkButton)e.Item.FindControl("lnkCancel");

LinkButton lnkEdit = (LinkButton)e.Item.FindControl("lnkEdit");

Label lbl_id = (Label)e.Item.FindControl("lbl_id");

Label lblfirstname = (Label)e.Item.FindControl("lblfirstname");

Label lbllastname = (Label)e.Item.FindControl("lbllastname");

Label lbluser = (Label)e.Item.FindControl("lbluser");

Label lblemail = (Label)e.Item.FindControl("lblemail");

Label lblgender = (Label)e.Item.FindControl("lblgender");

Label lbldob = (Label)e.Item.FindControl("lbldob");

Label lblphone = (Label)e.Item.FindControl("lblphone");

Label lbladdress = (Label)e.Item.FindControl("lbladdress");

TextBox txtfirstname = (TextBox)e.Item.FindControl("txtfirstname");

TextBox txtlastname = (TextBox)e.Item.FindControl("txtlastname");

TextBox txtuser = (TextBox)e.Item.FindControl("txtuser");

TextBox txtemail = (TextBox)e.Item.FindControl("txtemail");

TextBox txtgender = (TextBox)e.Item.FindControl("txtgender");

TextBox txtdob = (TextBox)e.Item.FindControl("txtdob");

TextBox txtphone = (TextBox)e.Item.FindControl("txtphone");

TextBox txtaddress = (TextBox)e.Item.FindControl("txtaddress");

if (e.CommandName == "edit")

{

lnkCancel.Visible = true;

lnkUpdate.Visible = true;

lnkEdit.Visible = false;

lblfirstname.Visible = false;

txtfirstname.Visible = true;

lbllastname.Visible = false;

txtlastname.Visible = true;

lbluser.Visible = false;

txtuser.Visible = true;

lblemail.Visible = false;

txtuser.Visible = true;

lblgender.Visible = false;

txtgender.Visible = true;

lbldob.Visible = false;

txtdob.Visible = true;

lblphone.Visible = false;

txtphone.Visible = true;

lbladdress.Visible = false;

txtaddress.Visible = true;

}

if (e.CommandName == "cancel")

{

BindRepeater();

}

if (e.CommandName == "update")

{

string s2 = Session["userid"].ToString();

int i = Convert.ToInt32(s2);

SqlConnection SqlCnn = new SqlConnection(s1);

SqlCommand SqlCmd = new SqlCommand("update mla_registration set firstname=@firstname,lastname=@lastname,username=@username,email=@email,gender=@gender,dob=@dob,phoneno=@phoneno,address=@address where user_id=@user_id", SqlCnn);

SqlCmd.Parameters.Add("@firstname", SqlDbType.VarChar).Value = txtfirstname.Text;

SqlCmd.Parameters.Add("@lastname", SqlDbType.VarChar).Value = txtlastname.Text;

SqlCmd.Parameters.Add("@username", SqlDbType.VarChar).Value = txtuser.Text;

SqlCmd.Parameters.Add("@email", SqlDbType.VarChar).Value = txtemail.Text;

SqlCmd.Parameters.Add("@gender", SqlDbType.VarChar).Value = txtgender.Text;

SqlCmd.Parameters.Add("@dob", SqlDbType.VarChar).Value = txtdob.Text;

SqlCmd.Parameters.Add("@phoneno", SqlDbType.VarChar).Value = txtphone.Text;

SqlCmd.Parameters.Add("@address", SqlDbType.VarChar).Value = txtaddress.Text;

SqlCmd.Parameters.Add("@user_id", SqlDbType.VarChar).Value = e.CommandArgument;

try

{

SqlCnn.Open();

SqlCmd.ExecuteNonQuery();

}

catch (Exception ex)

{

ex.Message.ToString();

}

finally

{

if (SqlCnn.State == ConnectionState.Open)

SqlCnn.Close();

}

BindRepeater();

}

}

kindly help me to sort this issue...

i have used session concept for viewing the details..

for viewing, no problem..

getting error while updating...