how to Execute update command

yeah the reason you r getting error is
1. you r not opening the connection
2. if you r opening the connection then Why u r storing cmd1.ExecuteNonQuery() in int i ?

the you r executing get stores in variable i and you are not executing it.

Simply remove int i just write




SqlCommand cmd1 = new SqlCommand();
SqlConnection con = new SqlConnection(@"Data Source=.\sqlexpress;Initial Catalog=DB;Integrated Security=True;Pooling=False");
protected void Page_Load(object sender, EventArgs e)
{
cmd1.Connection = con;
con.Open();
string tea_que, tea_ans;
using (cmd1 = new SqlCommand("SELECT que , ans FROM Que1 WHERE que_id =27", con))
{
using (SqlDataReader reader = cmd1.ExecuteReader())
{
while (reader.Read())
{
tea_que = (string)reader["que"];//for fetching values from table
tea_ans = (string)reader["ans"];
TextBox1.Text = tea_que;
TextBox2.Text = tea_ans;
}
}
//con.Close();
}
}

protected void update_Click(object sender, EventArgs e)
{
try
{
cmd1 = new SqlCommand("UPDATE Que1 SET que='" + TextBox1.Text + "',ans='" + TextBox2.Text + "' WHERE que_id='" + Label5.Text + "'", con);
cmd1.Parameters.Add("@que_id12",SqlDbType.Int).Value= Label5.Text;
cmd1.Parameters.Add("@que",SqlDbType.VarChar).Value= TextBox1.Text;
cmd1.Parameters.Add("@que_ans",SqlDbType.VarChar).Value= TextBox2.Text;
con.Open();
/*********** Dont store value in int i if you ll do it will not execute your code.***************
cmd1.ExecuteNonQuery();
con.Close();
Response.Write("changed");
TextBox1.Text = "";
TextBox2.Text = "";
}
catch (Exception e1)
{
Label3.Text = "not updated successfully"+e1;
}
}

cmd1 = new SqlCommand("UPDATE Que1 SET que='" + TextBox1.Text + "',ans='" + TextBox2.Text + "' WHERE que_id='" + Label5.Text + "'", con);
                cmd1.Parameters.Add("@que_id12",SqlDbType.Int).Value= Label5.Text;
                cmd1.Parameters.Add("@que",SqlDbType.VarChar).Value= TextBox1.Text;
                cmd1.Parameters.Add("@que_ans",SqlDbType.VarChar).Value= TextBox2.Text;

underlined que-id is int "+ label.text+"

First of all don't name your variables like conn1, cmd2, Label8, it's bad practice.
Many articles, chapters and so on have been written about it.

Also if there is no special reason for using single SqlCommand for entire class.

Convert string values to numeric, because:

object os = "5";
object on = 5;

are not same thing.

Use try/catch/finally block and close connection there. If necessary read about it.

For your basic problem try this:

protected void update_Click(object sender, EventArgs e)
{
    string updateQuery = "UPDATE Que1 SET que=@que, ans=@que_ans WHERE que_id=@que_id";

    try
    {
        using(SqlCommand cmd = new SqlCommand(updateQuery , con))
        {
             cmd.Parameters.Add("@que_id",SqlDbType.Int).Value = int.Parse(Label5.Text);
             cmd.Parameters.Add("@que",SqlDbType.VarChar).Value = TextBox1.Text;
             cmd.Parameters.Add("@que_ans",SqlDbType.VarChar).Value = TextBox2.Text;
              
             if(con.State != ConnectionState.Open)
             {
                 con.Open();
             }

             cmd.ExecuteNonQuery();
               
             Response.Write("changed");
             TextBox1.Text = string.Empty;
             TextBox2.Text = string.Empty;
         }
     }
     catch (Exception ex)
     {
        //Seriously adopt standard naming convention ;)
        Label3.Text = string.Format("Not updated successfully {0}",ex);
     }
     finally
     {
        if(con.State != ConnectionState.Closed)
        {
            con.Close();
        }
     }
}

I hope this helps.