Execute Query from another function - asp.net

Question

I want to execute a query on a button click event.
But that query is written in another function.
Here is my code, and it's not working. What is my problem?
namespace MCE_Member_Registration
{
public partial class registration_form_view : System.Web.UI.Page
{
SqlConnection conn = new SqlConnection("ConnectionString");
SqlCommand cmd;
protected void Page_Load(object sender, EventArgs e)
{
createform();
}
protected void createform() {
NameValueCollection nvc = Request.Form;
surname.Text = nvc["txt_surname"];
cmd.CommandText = "Insert into mce_applicants_information values(N'" + nvc["txt_surname"] + "')";
}
protected void confirm_Click(object sender, EventArgs e)
{
conn.Open();
cmd.ExecuteNonQuery();
conn.Close();
}
}
}

Answer 1

I'm not sure if this solves your problem. But if you really need another method to create your command, let it return it.
protected SqlCommand GetCommand()
{
SqlCommand cmd = new SqlCommand("Insert into blahblah values(blahblah)", connection);
return cmd;
}
protected void Button1_Click() {
connection.Open();
GetCommand().ExecuteNonQuery();
connection.Close();
}
Note that this is not best-practise due to several reasons. The connection should be closed even if an exception occured so use using statement instead. But that would be a problem in this approach since the connection is a field.
So i would prefer the all-in-one method approach which also uses parameters tro prevent sql-injection attacks:
protected void Button1_Click()
{
ExecuteBlahBlahCommand("blahblah");
}
private void ExecuteBlahBlahCommand(string blaColumnVal)
{
const string sql = "Insert into blahblah values(#blaColumn)";
using (var con = new SqlConnection(connectionString))
using (var cmd = new SqlCommand(sql, con))
{
cmd.Parameters.AddWithValue("#blaColumn", blaColumnVal);
con.Open();
cmd.ExecuteNonQuery();
}
}

Answer 2

I suggest you to use CommandText property and not contructor, because instance of cmd is created before this code, so you adjust your property
protected void CreateQuery() {
cmd.CommandText = "Insert into blahblah values(blahblah)";
}
protected void Button1_Click() {
connection.Open();
CreateQuery();
cmd.ExecuteNonQuery();
connection.Close();
}

Answer 3

Answering the question itself - Any variable you declare inside a function cannot be seen outside that function. You need to declare the SqlCommand in the correct scope...
For instance:
SqlCommand cmd;
protected void CreateQuery()
{
cmd = new SqlCommand("Insert into blahblah values(blahblah),connection)";
}
protected void Button1_Click()
{
CreateQuery();
connection.Open();
cmd.ExecuteNonQuery();
connection.Close();
}
This will declare the variable in the class level, and be accessible to all other methods in that class.
I'll just mention that #Tim Schmelter's answer is a good solution that might better suit your needs.