解决跨域问题的基本步骤

 安装包：Install-Package Microsoft.AspNet.WebApi.Cors

安装完成后，在配置文件后新增代码：

using System.Web.Http;
namespace WebService
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // New code
            config.EnableCors();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }
}

在Controllers上引用：using System.Web.Http.Cors;

在对应的方法或者类做控制

using System.Net.Http;
using System.Web.Http;
using System.Web.Http.Cors;

namespace WebService.Controllers
{
    [EnableCors(origins: "http://mywebclient.azurewebsites.net", headers: "*", methods: "*")]
    public class TestController : ApiController
    {
        // Controller methods not shown...
    }
}

在安装后编译出现问题：

错误    1    “TDServer.Areas.HelpPage.XmlDocumentationProvider”不实现接口成员“System.Web.Http.Description.IDocumentationProvider.GetResponseDocumentation(System.Web.Http.Controllers.HttpActionDescriptor)”    c:UsersAdministratorDesktopTDServerTDServerAreasHelpPageXmlDocumentationProvider.cs    14    18    TDServer
错误    2    “TDServer.Areas.HelpPage.XmlDocumentationProvider”不实现接口成员“System.Web.Http.Description.IDocumentationProvider.GetDocumentation(System.Web.Http.Controllers.HttpControllerDescriptor)”    c:UsersAdministratorDesktopTDServerTDServerAreasHelpPageXmlDocumentationProvider.cs    14    18    TDServer
警告    3    发现同一依赖程序集的不同版本间存在冲突。在 Visual Studio 中，请双击此警告(或选择此警告并按 Enter)以修复冲突；否则，请将以下绑定重定向添加到应用程序配置文件中的“runtime”节点: <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><dependentAssembly><assemblyIdentity name="System.Net 

.Http.Formatting" culture="neutral" publicKeyToken="31bf3856ad364e35" /><bindingRedirect oldVersion="0.0.0.0-5.2.4.0 

" newVersion="5.2.4.0 

" /></dependentAssembly></assemblyBinding><assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><dependentAssembly><assemblyIdentity name="System.Web.Http" culture="neutral" publicKeyToken="31bf3856ad364e35" /><bindingRedirect oldVersion="0.0.0.0-5.2.4.0 

" newVersion="5.2.4.0 

" /></dependentAssembly></assemblyBinding><assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><dependentAssembly><assemblyIdentity name="Newtonsoft.Json" culture="neutral" publicKeyToken="30ad4fe6b2a6aeed" /><bindingRedirect oldVersion="0.0.0.0-6.0.0.0 

" newVersion="6.0.0.0 

" /></dependentAssembly></assemblyBinding>    TDServer

安装包：Install-Package Microsoft.AspNet.WebApi -IncludePrerelease

安装后解决第三个问题。 

安装包：install-package Microsoft.AspNet.WebApi.HelpPage