@{
    ViewBag.Username = "Charlie Brown";
    string title1 = string.Format("Welcome {0}", ViewBag.Username);
    var title2 = string.Format("Welcome {0}", ViewBag.Username);
}

@Html.ActionLink(title1, "Index")
@Html.ActionLink(title2, "Index")

dynamic x = "";
int i = string.Format("{0}", x);