session variable for username - asp.net

Question

Hey I am creating a forum where users can login and post ocmments in a forum, I want the username as a session variable so I can get it when they post a comment and insert the username in the db and also to display a hello user message.
Below is my login code:
protected void Button1_Click(object sender, EventArgs e)
{
DataSet ds = new DataSet();
localhost.Service1 myws = new localhost.Service1();
ds = myws.GetUsers();
foreach (DataRow row in ds.Tables[0].Rows)
if (txtusername.Text == System.Convert.ToString(row["username"]) &&
txtpassword.Text == System.Convert.ToString(row["password"]))
{
System.Web.Security.FormsAuthentication.RedirectFromLoginPage(txtusername.Text, false);
}
else
Label3.Text = "Invalid Username/Password";
}
Do I declare the session variable here?
Like:
Session["username"] = "username";
Also not sure what to type to get the value username from the db
Thanks

Answer 1

You don't need to use a session. Once you call the FormsAuthentication.RedirectFromLoginPage method, inside the target page you could access the currently connected user from the authentication cookie that was emitted by this method using User.Identity.Name.
protected void Page_Load(object sender, EventArgs e)
{
if (User.Identity.IsAuthenticated)
{
string username = User.Identity.Name;
// ...
}
}
To learn more about how Forms Authentication works in ASP.NET I invite you to read the following article.

Answer 2

You are already using forms authentication (FormsAuthentication.RedirectFromLoginPage(txtusername.Text, false)) which is great. Consequently, you don't need to store the username is session as it's already available via User.Identity.Name, as Darin noted.
I have written two tutorials on forms authentication you might find useful:
An Overview of Forms Authentication
Forms Authentication Configuration and Advanced Topics
Additionally, consider using Membership. Membership is a subsystem built into ASP.NET that handles user accounts and provides an API for creating accounts, deleting accounts, etc. In short, you don't have to write all that code yourself. And with the login Web controls, creating new accounts, signing users in, resetting passwords, and so on, are all quite simple and involve zero to little code. For more information see my Membership tutorials.
Happy Programming!