MVC Query string Session

Query String :
while redirecting from controller we can pass Query string as follows:
return Redirect("/Customer/CustomerHome?username=" + username);

Now to use Query String on respective page use below code 
<h4>Welcome @Request.QueryString["username"]</h4>

** Now if you want that this Username is displayed over all pages using "Session" is a better Idea 

Use Session variable in controller  as follows
Session["username"] = username;

To use this session variable on all page
<div class="col-md-3">Welcome @Session["username"]</div> 
Better way include this session variable in _layout file