Earlier today Scott Guthrie announced the ASP.NET MVC 3 - Release Candidate 2. I installed the new version right after the announcement since I was eager to see the new features. Among other cool features included in this release candidate, there is a new ViewBag dynamic which can be used to pass data from Controllers to Views same as you use ViewData[] dictionary. What is great and nice about ViewBag (despite the name) is that its a dynamic type which means you can dynamically get/set values and add any number of additional fields without need of strongly-typed classes.
In order to see the difference, please take a look at the following examples.
Example - Using ViewData
Controller
public ActionResult Index()
{
List<string> colors = new List<string>();
colors.Add("red");
colors.Add("green");
colors.Add("blue");
ViewData["listColors"] = colors;
ViewData["dateNow"] = DateTime.Now;
ViewData["name"] = "Hajan";
ViewData["age"] = 25;
return View();
}
View (ASPX View Engine)
<p>
My name is
<b><%: ViewData["name"] %></b>,
<b><%: ViewData["age"] %></b> years old.
<br />
I like the following colors:
</p>
<ul id="colors">
<% foreach (var color in ViewData["listColors"] as List<string>){ %>
<li>
<font color="<%: color %>"><%: color %></font>
</li>
<% } %>
</ul>
<p>
<%: ViewData["dateNow"] %>
</p>
(I know the code might look cleaner with Razor View engine, but it doesn’t matter right? ;) )
Example - Using ViewBag
Controller
public ActionResult Index()
{
List<string> colors = new List<string>();
colors.Add("red");
colors.Add("green");
colors.Add("blue");
ViewBag.ListColors = colors; //colors is List
ViewBag.DateNow = DateTime.Now;
ViewBag.Name = "Hajan";
ViewBag.Age = 25;
return View();
}
You see the difference?
View (ASPX View Engine)
<p>
My name is
<b><%: ViewBag.Name %></b>,
<b><%: ViewBag.Age %></b> years old.
<br />
I like the following colors:
</p>
<ul id="colors">
<% foreach (var color in ViewBag.ListColors) { %>
<li>
<font color="<%: color %>"><%: color %></font>
</li>
<% } %>
</ul>
<p>
<%: ViewBag.DateNow %>
</p>
In my example now I don’t need to cast ViewBag.ListColors as List<string> since ViewBag is dynamic type! On the other hand the ViewData[“key”] is object.
I would like to note that if you use ViewData["ListColors"] = colors; in your Controller, you can retrieve it in the View by using ViewBag.ListColors.
And the result in both cases is
Hope you like it!
Regards,
Hajan