ViewData                                                                           ViewBag 
它是Key/Value字典集合                                                                       它是dynamic类型对像 
从Asp.net MVC 1 就有了                                                                      ASP.NET MVC3 才有 
基于Asp.net 3.5 framework                                                                 基于Asp.net 4.0与.net framework 
ViewData比ViewBag快                                                                        ViewBag比ViewData慢 
在ViewPage中查询数据时需要转换合适的类型                               在ViewPage中查询数据时不需要类型转换 
有一些类型转换代码                                                                              可读性更好 

用代码说明问题：

后台：

ViewData：
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();

ViewBag：
List<string> colors = new List<string>();
colors.Add("red");
colors.Add("green");
colors.Add("blue");
ViewBag.ListColors = colors; 
ViewBag.DateNow = DateTime.Now;
ViewBag.Name = "Hajan";
ViewBag.Age = 25;
return View(); 

前台：

ViewData：
<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>

ViewBag：
<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>

本文代码部分转自：http://blog.csdn.net/a497785609/article/details/7854402

mvc中viewdata 和viewbag的区别