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Web Api的优缺点就不说了，直接说怎么跨域，我搜了一下，主要是有两种。
一，ASP.NET Web API支持JSONP，分两种
1，利用JsonMediaTypeFormatter，具体参考这里： http://www.cnblogs.com/artech/p/cors-4-asp-net-web-api-03.html
上代码：
新建JsonpMediaTypeFormatter类：
public class JsonpMediaTypeFormatter : JsonMediaTypeFormatter
{
private string callbackQueryParameter;
public JsonpMediaTypeFormatter()
{
SupportedMediaTypes.Add(DefaultMediaType);
SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/javascript"));
MediaTypeMappings.Add(new UriPathExtensionMapping("jsonp", DefaultMediaType));
}
public string CallbackQueryParameter
{
get { return callbackQueryParameter ?? "callback"; }
set { callbackQueryParameter = value; }
}
/// <summary>
/// 将对象序列化后的JSON字符串填充到JavaScript回调函数中
/// </summary>
/// <param name="type"></param>
/// <param name="value"></param>
/// <param name="stream"></param>
/// <param name="content"></param>
/// <param name="transportContext"></param>
/// <returns></returns>
public override Task WriteToStreamAsync(Type type, object value, Stream stream, HttpContent content, TransportContext transportContext)
{
string callback;
if (IsJsonpRequest(out callback))
{
return Task.Factory.StartNew(() =>
{
var writer = new StreamWriter(stream);
writer.Write(callback + "(");
writer.Flush();
base.WriteToStreamAsync(type, value, stream, content, transportContext).Wait();
writer.Write(")");
writer.Flush();
});
}
else
{
return base.WriteToStreamAsync(type, value, stream, content, transportContext);
}
}
/// <summary>
/// 判断是否为跨域请求
/// </summary>
/// <param name="callback"></param>
/// <returns></returns>
private bool IsJsonpRequest(out string callback)
{
callback = null;
if (HttpContext.Current.Request.HttpMethod != "GET")
return false;
callback = HttpContext.Current.Request.QueryString[CallbackQueryParameter];
return !string.IsNullOrEmpty(callback);
}
}在Global.asax中注册JsonpMediaTypeFormatter
GlobalConfiguration.Configuration.Formatters.Insert(0, new JsonpMediaTypeFormatter());
2，利用ActionFilterAttribute ，具体参考这里： http://stackoverflow.com/questions/9421312/jsonp-with-asp-net-web-api/18206518#18206518
代码：
新建 JsonCallbackAttribute 类
public class JsonCallbackAttribute : ActionFilterAttribute
{
private const string CallbackQueryParameter = "callback";
public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
{
var callback = string.Empty;
if (IsJosnp(out callback))
{
var jsonBuilder = new StringBuilder(callback);
jsonBuilder.AppendFormat("({0})", actionExecutedContext.Response.Content.ReadAsStringAsync().Result);
actionExecutedContext.Response.Content = new StringContent("C(\"a\")");
}
base.OnActionExecuted(actionExecutedContext);
}
private bool IsJosnp(out string callback)
{
callback = System.Web.HttpContext.Current.Request.QueryString[CallbackQueryParameter];
return !string.IsNullOrEmpty(callback);
}
}在Global.asax中注册JsonCallbackAttribute
GlobalConfiguration.Configuration.Filters.Add(new JsonCallbackAttribute());
二，使用 Microsoft ASP.NET Web API 2 Cross-Origin Suppor
使用 NuGe 安装 Microsoft ASP.NET Web API 2 Cross-Origin Support，这里说的很详细
然后在Global.asax中开启针对CORS的支持，EnableCors加不加无影响的样子。
测试实例：
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script src="http://cdn.bootcss.com/jquery/2.1.3/jquery.min.js"></script>
<title>测试 WebApi 跨域</title>
</head>
<body>
<form id="form1" runat="server">
<input type="button" id="btnGet" value="Get 点击跨域查询数据" />
<div id="bindData">
</div>
<input type="button" id="btnPost" value="Post 点击跨域查询数据" />
</form>
<script>
$('#btnGet').bind('click', function (e) {
$.ajax({
type: "GET",
url: "http://localhost:20128/api/UserInfo",
success: function (data) {
var html = "";
$.each(data, function (index, val) {
html += "<ul><li>GroupName: " + val.Id + " -- " + val.Name + "</li></ul>";
});
$("#bindData").append(html);
}
});
});
$('#btnPost').bind('click', function (e) {
var user = { Id: '1', Name: '233' };
$.ajax({
type: "POST",
contentType: 'application/json; charset=utf-8',
data: JSON.stringify(user),
url: "http://localhost:20128/api/UserInfo",
success: function (data) {
//var html = "";
//$.each(data, function (index, val) {
//html += "<ul><li>GroupName: " + val.Id + " -- " + val.Name + "</li></ul>";
//});
//$("#bindData").append(html);
}
});
});
</script>
</body>
</html>Ajax请求在Post数据的时候，一定要加上这样项：
contentType: 'application/json; charset=utf-8',
data: JSON.stringify(user),
就这样，只是把网络上有解决方案的整理了一下，放在了一切。