What does the @ in front of a parameter name do?

Question

What does the @ sign does when inserted in front of parameters SQL query?

for example:

using (SqlCommand cmd = new SqlCommand("INSERT INTO [User] values (@Forename, @Surname, @Username, @Password)", con))
{
    cmd.Parameters.AddWithValue("@Forename", txtForename.Text);
    cmd.Parameters.AddWithValue("@Surname", txtSurname.Text);
    cmd.Parameters.AddWithValue("@UserName", txtUsername.Text);
    cmd.Parameters.AddWithValue("@Password", txtPassword.Text);

    cmd.ExecuteNonQuery();
}

Answer 1

That's just what indicates that it is a parameter name in the query - as opposed to trying to use a field from the column.

It's not clear whether it's strictly needed when constructing the SqlParameter object, but I think it makes sense to be consistent :)