JSONP可以帮我们解决跨域访问的问题。JSONP is JSON With Padding. 这里我们将不再解释其原理。我们来看在ASP.NET MVC 3 如何实现。首先我们需要定义一个JsonpResult. 代码像这样, 直接继承自JsonResult, override了ExecuteResult方法
public class JsonpResult : JsonResult { private static readonly string JsonpCallbackName = "callback"; private static readonly string CallbackApplicationType = "application/json"; /// <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 within which the result is executed.</param> /// <exception cref="T:System.ArgumentNullException">The <paramref name="context"/> parameter is null.</exception> public override void ExecuteResult(ControllerContext context) { if (context == null) { throw new ArgumentNullException("context"); } if ((JsonRequestBehavior == JsonRequestBehavior.DenyGet) && String.Equals(context.HttpContext.Request.HttpMethod, "GET")) { throw new InvalidOperationException(); } var response = context.HttpContext.Response; if (!String.IsNullOrEmpty(ContentType)) response.ContentType = ContentType; else response.ContentType = CallbackApplicationType; if (ContentEncoding != null) response.ContentEncoding = this.ContentEncoding; if (Data != null) { String buffer; var request = context.HttpContext.Request; var serializer = new JavaScriptSerializer(); if (request[JsonpCallbackName] != null) buffer = String.Format("{0}({1})", request[JsonpCallbackName], serializer.Serialize(Data)); else buffer = serializer.Serialize(Data); response.Write(buffer); } } }
接着简单定义一个扩展方法:
public static class ContollerExtensions { /// <summary> /// Extension methods for the controller to allow jsonp. /// </summary> /// <param name="controller">The controller.</param> /// <param name="data">The data.</param> /// <returns></returns> public static JsonpResult Jsonp(this Controller controller, object data) { JsonpResult result = new JsonpResult() { Data = data, JsonRequestBehavior = JsonRequestBehavior.AllowGet }; return result; } }
在Controller里使用它, 我们的Controller叫ApiController，其中的Action:
/// <summary> /// Get some basic information with a JSONP GET request. /// </summary> /// <remarks> /// Sample url: /// http://localhost:50211/Api/GetInformation?key=test&callback=json123123 /// </remarks> /// <param name="key">key</param> /// <returns>JsonpResult</returns> public JsonpResult GetInformation(string key) { var resp = new Models.CustomObject(); if (ValidateKey(key)) { resp.Data = "You provided key: " + key; resp.Success = true; } else { resp.Message = "unauthorized"; } return this.Jsonp(resp); } private bool ValidateKey(string key) { if (!string.IsNullOrEmpty(key)) return true; return false; }
上面的方法接收一个string的参数，接着我们在前面加一个前缀字符串，最后返回就是Jsonp Result.
传值的Model:
public class CustomObject
{
public bool Success { get; set; }
public object Data { get; set; }
public string Message { get; set; }
}
运行WebSite， 访问 http://localhost:50211/Api/GetInformation?callback=myfunction&key=haha
我们可以看到这样的结果:
myfunction({"Success":true,"Data":"You provided key: haha","Message":null})
好的，现在让我们在另一个站点里使用它：
<html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title>Index</title> <script src="../../Scripts/jquery-1.4.1.min.js" type="text/javascript"></script> <script type="text/javascript"> $(document).ready(function () { $('.result').hide(); $('#test').click(function () { $('.result').fadeOut('fast'); $('.result').html(''); $.ajax({ url: 'http://localhost:50211/Api/GetInformation', data: { key: $('input[name=key]').val() }, type: "GET", dataType: "jsonp", jsonpCallback: "localJsonpCallback" }); }); }); function localJsonpCallback(json) { //do stuff... if (json.Success) { $('.result').html(json.Data); } else { $('.result').html(json.Message); } $('.result').fadeIn('fast'); } </script> </head> <body> <div> Enter key: <input type="text" name="key" value="some data key, this parameter is optional" /> <br /><input type="button" value="Test JSONP" id="test" /> <div class="result"> </div> </div> </body> </html>
这里使用的JQuery的Ajax来调用它, 熟悉JQuery的应该能看懂， 结果是在button下div显示字符串:
You provided key: some data key, this parameter is optional
在这里，也可以使用getJSON方法。
好了，就这么简单。希望对您Web开发有帮助。
摘自：http://www.cnblogs.com/wintersun/archive/2012/05/25/2518572.html