我们通过将这一行添加到我们的 WebApiConfig.cs 文件中解决了这个问题
config.Services.Replace(typeof(IHttpControllerSelector), new AcceptHeaderControllerSelector(config));
我使用的核心方法如下 这个方法是在扩展 IHttpControllerSelector 接口的 AcceptHeaderControllerSelector 类中。
我这样做的原因是我们必须对 API 进行版本控制，这是一种创建新控制器的方法，例如V2 仅使用我们版本化的方法，如果 V2 不存在，则返回到 V1
private HttpControllerDescriptor TryGetControllerWithMatchingMethod(string version, string controllerName, string actionName)
{
var versionNumber = Convert.ToInt32(version.Substring(1, version.Length - 1));
while(versionNumber >= 1) {
var controllerFullName = string.Format("Namespace.Controller.V{0}.{1}Controller, Namespace.Controller.V{0}", versionNumber, controllerName);
Type type = Type.GetType(controllerFullName, false, true);
var matchFound = type != null && type.GetMethod(actionName) != null;
if (matchFound)
{
var key = string.Format(CultureInfo.InvariantCulture, "V{0}{1}", versionNumber, controllerName);
HttpControllerDescriptor controllerDescriptor;
if (_controllers.TryGetValue(key, out controllerDescriptor))
{
return controllerDescriptor;
}
}
versionNumber--;
}
return null;
}
完整文件如下：
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Reflection;
using System.Web.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Dispatcher;
using System.Web.Http.Routing;
namespace WebApi
{
public class AcceptHeaderControllerSelector : IHttpControllerSelector
{
private const string ControllerKey = "controller";
private const string ActionKey = "action";
private const string VersionHeaderValueNotFoundExceptionMessage = "Version not found in headers";
private const string VersionFoundInUrlAndHeaderErrorMessage = "Version can not be in Header and Url";
private const string CouldNotFindEndPoint = "Could not find endpoint {0} for api version number {1}";
private readonly HttpConfiguration _configuration;
private readonly Dictionary<string, HttpControllerDescriptor> _controllers;
public AcceptHeaderControllerSelector(HttpConfiguration config)
{
_configuration = config;
_controllers = InitializeControllerDictionary();
}
private Dictionary<string, HttpControllerDescriptor> InitializeControllerDictionary()
{
var dictionary = new Dictionary<string, HttpControllerDescriptor>(StringComparer.OrdinalIgnoreCase);
var assembliesResolver = _configuration.Services.GetAssembliesResolver();
// This would seem to look at all references in the web api project and find any controller, so I had to add Controller.V2 reference in order for it to find them
var controllersResolver = _configuration.Services.GetHttpControllerTypeResolver();
var controllerTypes = controllersResolver.GetControllerTypes(assembliesResolver);
foreach (var t in controllerTypes)
{
var segments = t.Namespace.Split(Type.Delimiter);
// For the dictionary key, strip "Controller" from the end of the type name.
// This matches the behavior of DefaultHttpControllerSelector.
var controllerName = t.Name.Remove(t.Name.Length - DefaultHttpControllerSelector.ControllerSuffix.Length);
var key = string.Format(CultureInfo.InvariantCulture, "{0}{1}", segments[segments.Length - 1], controllerName);
dictionary[key] = new HttpControllerDescriptor(_configuration, t.Name, t);
}
return dictionary;
}
public HttpControllerDescriptor SelectController(HttpRequestMessage request)
{
IHttpRouteData routeData = request.GetRouteData();
if (routeData == null)
{
throw new HttpResponseException(HttpStatusCode.NotFound);
}
var controllerName = GetRouteVariable<string>(routeData, ControllerKey);
var actionName = GetRouteVariable<string>(routeData, ActionKey);
if (controllerName == null)
{
throw new HttpResponseException(HttpStatusCode.NotFound);
}
var version = GetVersion(request);
HttpControllerDescriptor controllerDescriptor;
if (_controllers.TryGetValue(controllerName, out controllerDescriptor))
{
if (!string.IsNullOrWhiteSpace(version))
{
throw new HttpResponseException(request.CreateResponse(HttpStatusCode.Forbidden, VersionFoundInUrlAndHeaderErrorMessage));
}
return controllerDescriptor;
}
controllerDescriptor = TryGetControllerWithMatchingMethod(version, controllerName, actionName);
if (controllerDescriptor != null)
{
return controllerDescriptor;
}
var message = string.Format(CouldNotFindEndPoint, controllerName, version);
throw new HttpResponseException(request.CreateResponse(HttpStatusCode.NotFound, message));
}
private HttpControllerDescriptor TryGetControllerWithMatchingMethod(string version, string controllerName, string actionName)
{
var versionNumber = Convert.ToInt32(version.Substring(1, version.Length - 1));
while(versionNumber >= 1) {
var controllerFullName = string.Format("Namespace.Controller.V{0}.{1}Controller, Namespace.Controller.V{0}", versionNumber, controllerName);
Type type = Type.GetType(controllerFullName, false, true);
var matchFound = type != null && type.GetMethod(actionName) != null;
if (matchFound)
{
var key = string.Format(CultureInfo.InvariantCulture, "V{0}{1}", versionNumber, controllerName);
HttpControllerDescriptor controllerDescriptor;
if (_controllers.TryGetValue(key, out controllerDescriptor))
{
return controllerDescriptor;
}
}
versionNumber--;
}
return null;
}
public IDictionary<string, HttpControllerDescriptor> GetControllerMapping()
{
return _controllers;
}
private string GetVersion(HttpRequestMessage request)
{
IEnumerable<string> values;
string apiVersion = null;
if (request.Headers.TryGetValues(Common.Classes.Constants.ApiVersion, out values))
{
apiVersion = values.FirstOrDefault();
}
return apiVersion;
}
private static T GetRouteVariable<T>(IHttpRouteData routeData, string name)
{
object result = null;
if (routeData.Values.TryGetValue(name, out result))
{
return (T)result;
}
return default(T);
}
}
}