使用Post/Redirect/Get实现Asp.net防止表单重复提交

前面的Post有提到解决Web中表单重复提交的方法，实际上表单重复提交的问题不单是Asp.net，其它动态Page都有。让我们看下面的图示:

然后在刷新页面时经常看到提示框在IE中:

Google Chrome:

Firefox:

最简单的解决方法就是使用Post-Redirect-Get模式，就是Http-Post完后，马上做Redirect操作，接下来那个页面是Get。这时用户强制按F5刷新也没有用了。最终实现的效果图：

那在Asp.net MVC中如何去做呢，看下面简单View代码：

一个包含两个Input的表单:
<form method="post" id="form1" action="/Security/LoginVerify">
    <p>
       UserName:<input type="text" id="fusername" name="fusername" /><br />
       Password:<input type="password" id="fpassword" name="fpassword" />
       <input type="submit" value="Sign-in" />
    </p>
    </form>
Index Action 在这里做Get的操作, LoginVerify 在这里是Post的目标Action
[HttpPost]
public ActionResult LoginVerify(string fusername, string fpassword)
{
    return this.RedirectToAction("Index", "Security", new { fusername = fusername });
}
public ActionResult Index(string fusername)
{
    ViewBag.UserName = fusername + " login success!";
    return View();
}

对应请求时的HTTP Request RAW是这样的:
POST http://localhost:91/Security/LoginVerify HTTP/1.1
Accept: text/html, application/xhtml+xml, */*
Referer: http://localhost:91/Security/Login
Accept-Language: en-US,zh-CN;q=0.5
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
Content-Type: application/x-www-form-urlencoded
Accept-Encoding: gzip, deflate
Host: localhost:91
Content-Length: 71
Connection: Keep-Alive
Pragma: no-cache
Cookie: ASP.NET_SessionId=qwwlp4rmjnzbsq3ob4dmcg3q

Http Response RAW:
HTTP/1.1 302 Found
Cache-Control: private
Content-Type: text/html; charset=utf-8
Location: /Security?fusername=admin
Server: Microsoft-IIS/7.5
X-AspNetMvc-Version: 3.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Sat, 24 Mar 2012 02:54:26 GMT
Content-Length: 142
<html><head><title>Object moved</title></head><body>
<h2>Object moved to <a href="/Security?fusername=admin">here</a>.</h2>
</body></html>
在现在大多数的Web应用程序中都使用是Http 302的重定向。Http 1.1说明书中引用HTTP 303就是用来应对这种用户提交表单后可以在浏览器安全的刷新场景。 HTTP 303 意义是这样的：
Used to tell the client that the resource should be fetched using a different URL. This
new URL is in the Location header of the response message. Its main purpose is to
allow responses to POST requests to direct a client to a resource.

在Asp.net MVC可以这些去实现一个自定义ActionResult:
/// <summary>
/// SeeOtherRedirectResult
/// </summary>
public class SeeOtherRedirectResult : ActionResult
{
private string _url;

    /// <summary>
    /// Initializes a new instance of the <see cref="SeeOtherRedirectResult"/> class.
    /// </summary>
    /// <param name="url">Target URL.</param>
    public SeeOtherRedirectResult(string url)
    {
        _url = url;
    }

    /// <summary>
    /// Enables processing of the result of an action method by a custom type that inherits from the <see cref="T:System.Web.Mvc.ActionResult"/> class.
    /// </summary>
    /// <param name="context">The context in which the result is executed. The context information includes the controller, HTTP content, request context, and route data.</param>
    public override void ExecuteResult(ControllerContext context)
    {
        context.HttpContext.Response.StatusCode = 303;
        context.HttpContext.Response.RedirectLocation = _url;
    }
}

然后Action中使用它，来实现Http 303的重定向。：
[HttpPost]
public ActionResult LoginVerify(string fusername, string fpassword)
{
return new SeeOtherRedirectResult(Url.Action("Index", "Security", new { fusername = fusername }));
}

运行时，我们来看Http Response RAW:
HTTP/1.1 303 See Other
Cache-Control: private
Location: /Security?fusername=admin
Server: Microsoft-IIS/7.5
X-AspNetMvc-Version: 3.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Sat, 24 Mar 2012 03:05:37 GMT
Content-Length: 0

完了，希望对您Web开发有帮助。如有任何问题请留言!

作者：Petter Liu

补充：Web开发 , ASP.Net ,