ViewData与ViewBag的区别

本文导读：在asp.net mvc程序设计中，传递数据常常会用到viewdata、viewbag。ViewData是一个字典集合，通过key值读取对应的value；ViewBag是动态类型，作用和ViewData一样，都是用来存储信息，有一些不同的是ViewData是object类型，ViewBag是动态类型。

视图数据可以通过ViewBag属性访问，它主要是为了从Controller到view进行传值用的，类似有所使用的ViewData[] 字典类。

一、ViewBag的定义

 

public dynamic ViewBag {
    get {
        if (_dynamicViewData == null) {
            _dynamicViewData = new DynamicViewDataDictionary(() => ViewData);
        }
        return _dynamicViewData;
    }
}    

二、ViewData的定义

public ViewDataDictionary ViewData {
    get {
        if (_viewData == null) {
            SetViewData(new ViewDataDictionary());
        }
        return _viewData;
    }
    set {
        SetViewData(value);
    }
}      

三、ViewData与ViewBag的区别

1、ViewData是字典类型，赋值方式用字典方式，通过key值读取对应的value， ViewData["myName"]

2、ViewBag是动态类型，使用时直接添加属性赋值即可 ViewBag.myName

3、ViewBag和ViewData只在当前Action中有效，等同于View

4、ViewData和ViewBag 中的值可以互相访问，因为ViewBag的实现中包含了ViewData

四、ViewData与ViewBag的实例

1、ViewData

（1）、在Controller中使用ViewData

public ActionResult UsingViewData()
{
    
    ViewData["Title"] = " Using ViewData";
    ViewData["ProjectName"] = "My Test Project";
    ViewData["ProjectDescription"] = "This is Test Project to demo Viewdata and viewbag details";
    ViewData["StartDate"] = new DateTime(2011, 1, 1);
    ViewData["TotalPrice"] = 1000;
    ViewData["TotalDays"] = 100;
    Dictionary<string, string> stackholder = new Dictionary<string, string>();
    stackholder.Add("Client","Mr.  Client");
    stackholder.Add("Manager","Mr. Joy");
    stackholder.Add("Team Leader","Mr.Toy");
    stackholder.Add("Sr. developer", "Mr.dojoy");
    stackholder.Add("developer", "Mr. nodoy");
    ViewData["stackholder"] = stackholder;

    List<string> modules = new List<string>();
    modules.Add("Admin module");
    modules.Add("ShoppingCart module");
    modules.Add("CMS module");
    ViewData["modules"] = modules;
    return View();
}    

（2）、对应UsingViewData View的cshtml

<h1>@ViewData["Title"]</h1>
 <div>
   <div>
    <h2>Project Name : @ViewData["ProjectName"]</h2>
   </div>
   <div>
     ProjectDescription :   
     <p>"@ViewData["ProjectDescription"]".</p>
   </div>
   <div>
      Stack Holder :
      <br />

      <ul id="stakholder">
      @foreach ( var stakerholder in ViewData["stackholder"] as Dictionary<string, string> )
      {          
    <li>
        @stakerholder.Key &nbsp; : @stakerholder.Value
    </li>
      }
     </ul>
   </div>
   <div>
     Project Details:<br />
     <div>
       module List  :
       <ul id="modulelist">
      @foreach ( var module in ViewData["modules"] as List<string> )
      {          
    <li>
        @module
    </li>
      }
     </ul>
        
     </div>
     Project StartDate : @ViewData["StartDate"]  <br />
     Project TotalPrice: @ViewData["TotalPrice"] <br />
     Project TotaDays  : @ViewData["TotalDays"] 
   </div>
 </div>      

2、ViewBag

（1）、在Controller中使用ViewBag

public ActionResult UsingViewBag()
{

    ViewBag.Title = " Using ViewBag";
    ViewBag.ProjectName = "My Test Project";
    ViewBag.ProjectDescription = "This is Test Project to demo Viewdata and viewbag details";
    ViewBag.StartDate = new DateTime(2011, 1, 1);
    ViewBag.TotalPrice = 1000;
    ViewBag.TotalDays = 100;
    Dictionary<string, string> stackholder = new Dictionary<string, string>();
    stackholder.Add("Client", "Mr.  Client");
    stackholder.Add("Manager", "Mr. Joy");
    stackholder.Add("Team Leader", "Mr.Toy");
    stackholder.Add("Sr. developer", "Mr.dojoy");
    stackholder.Add("developer", "Mr. nodoy");
    ViewBag.stackholder = stackholder;

    List<string> modules = new List<string>();
    modules.Add("Admin module");
    modules.Add("ShoppingCart module");
    modules.Add("CMS module");
    ViewBag.modules = modules;
    return View();
}

（2）、对应View UsingViewBag 的cshtml的ViewBag

<h1>@ViewBag.Title</h1>
 <div>
   <div>
    <h2>Project Name : @ViewBag.ProjectName</h2>
   </div>
   <div>
     ProjectDescription :   
     <p>"@ViewBag.ProjectDescription.</p>
   </div>
   <div>
      Stack Holder :
      <br />

      <ul id="stakholder">
      @foreach ( var stakerholder in ViewBag.stackholder )
      {          
    <li>
        @stakerholder.Key &nbsp; : @stakerholder.Value
    </li>
      }
     </ul>
   </div>
   <div>
     Project Details:<br />
     <div>
       module List  :
       <ul id="modulelist">
      @foreach ( var module in ViewBag.modules )
      {          
    <li>
        @module
    </li>
      }
     </ul>
        
     </div>
     Project StartDate : @ViewBag.StartDate.ToString("dd-MMM-yyyy") <br />
     Project TotalPrice: @ViewBag.TotalPrice  ₹  <br />
     Project TotaDays  : @ViewBag.TotalDays 
   </div>
 </div>