MVC中的ViewData、ViewBag和TempData

向右看齐 2021-09-17 15:04 271阅读 0赞

一、ViewBag和ViewData的定义

public dynamic ViewBag { get; }
    public ViewDataDictionary ViewData { get; set; }

二、ViewBag和ViewData的差别

<table style="font-family:SimHei;color:rgb(255,255,255);"> 
 <tbody> 
  <tr> 
   <td><strong><span style="color:#333333;"><span style="font-size:12px;">viewdata</span></span></strong></td> 
   <td><strong><span style="color:#333333;"><span style="font-size:12px;">viewbag</span></span></strong></td> 
  </tr> 
  <tr> 
   <td><span style="color:#333333;"><span style="font-size:12px;">它是key/value字典集合</span></span></td> 
   <td><span style="color:#333333;"><span style="font-size:12px;">它是dynamic类型对象</span></span></td> 
  </tr> 
  <tr> 
   <td><span style="color:#333333;"><span style="font-size:12px;">从asp.net mvc1就有了</span></span></td> 
   <td><span style="color:#333333;"><span style="font-size:12px;">从asp.netmvc3才有</span></span></td> 
  </tr> 
  <tr> 
   <td><span style="color:#333333;"><span style="font-size:12px;">基于asp.netframework 3.5</span></span></td> 
   <td><span style="color:#333333;"><span style="font-size:12px;">基于asp.net framework4.0</span></span></td> 
  </tr> 
  <tr> 
   <td><span style="color:#333333;"><span style="font-size:12px;">viewdata比viewbag快</span></span></td> 
   <td><span style="color:#333333;"><span style="font-size:12px;">viewbag比viewdata慢</span></span></td> 
  </tr> 
  <tr> 
   <td><span style="color:#333333;"><span style="font-size:12px;">页面查询数据时须要转换合适的类型</span></span></td> 
   <td><span style="color:#333333;"><span style="font-size:12px;">在页面查询数据时不须要转换合适的类型</span></span></td> 
  </tr> 
  <tr> 
   <td><span style="color:#333333;"><span style="font-size:12px;">有一些类型转换代码</span></span></td> 
   <td><span style="color:#333333;"><span style="font-size:12px;">可读性较好</span></span></td> 
  </tr> 
 </tbody> 
</table>

ViewBag不再是字典的键值对结构。而是dynamic动态类型，它会在程序执行的时候动态解析。

ViewBag.NumberObjs = new string[] { "one", "two", "three" };
                ViewData["NumberArrs"] = new string[] { "one", "two", "three" };
    
                //正确，dynamic类型的解析作用，foreach能够使用
                foreach (var item in ViewBag.NumberObjs)
                {
    
                }
    
                //错误：foreach语句不可作用于object类型对象上
                foreach (var item in ViewData["NumberArrs"])
                {
    
                }

1、ViewBag事实上本质就是ViewData，仅仅是多了层Dynamic控制。所以，使用何种方式全然取决于你的个人爱好。

2、ViewBag和ViewData仅针对当前Action中有效，生命周期和view同样。

三、TempData

保存在session中，Controller每次运行请求时。会从session中获取tempdata。而后清空session，获取完tempdata数据，尽管保存在内部字典中。

可是字典中每一个条目訪问一次后就从字典中删除。因此Tempdata数据最多仅仅能经过一次controller传递。而且每一个元素最多仅仅能訪问一次，之后删除。

四、举例

在Controller中使用ViewData:

<pre name="code" class="csharp">public ActionResult UsingViewData()
            {
                ViewData["Title"] = "Using ViewData";
                ViewData["ProjectName"] = "My Test Project";
                ViewData["ProjectDescription"] = "This is TestProject 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();
            }

<div><span style="color: rgb(35, 35, 35); font-family: Verdana, Arial, helvetica, sans-seriff; font-size: 14px; line-height: 25px; orphans: 2; text-align: -webkit-auto; widows: 2;">相应UsingViewData View的cshtml:</span></div><pre name="code" class="html">@{
        ViewBag.Title = "UsingViewData";
    }
    
    <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   : @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>

ViewBag controller：

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.doyjoy");
                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();
            }

相应的页面：

@{
        ViewBag.Title = "UsingViewBag";
    }
    
    <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   : @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>

五、总结

1、ViewData和TempData是字典类型，赋值方式用字典方式。ViewData**\["myName"\] **

2、ViewBag是动态类型，使用时直接加入属性赋值就可以 ViewBag.myName

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

4、TempData能够通过转向继续使用，由于它的值保存在Session中。但TempData仅仅能经过一次传递。之后会被系统自己主动清除

5、ViewData和ViewBag中的值能够互相訪问。由于ViewBag的实现中包括了ViewData