WebApi常见的实现方式有：FORM身份验证、集成WINDOWS验证、Basic基础认证、Digest摘要认证

个人偏好Basic基础认证，而且支持跨域，下面详解这种方式。

1.定义一个自定义属性类（BasicAuthorizeAttribute）继承自AuthorizationFilterAttribute：

public class BasicAuthorizeAttribute : AuthorizationFilterAttribute
    {
        public override void OnAuthorization(System.Web.Http.Controllers.HttpActionContext actionContext)
        {
            //如果用户使用了forms authentication，就不必在做basic authentication了
            if (Thread.CurrentPrincipal.Identity.IsAuthenticated)
            {
                return;
            }

            var url = actionContext.Request.RequestUri.AbsoluteUri;
            //var secretkey = actionContext.Request.RequestUri;
            var secretUrl = url.Split(new string[] { "key=" }, StringSplitOptions.RemoveEmptyEntries)[0].TrimEnd('&');
            if (url.Contains('?'))
            {
                var queryValue = url.Split('?')[1];
                if (!string.IsNullOrEmpty(queryValue) && !string.IsNullOrEmpty(secretUrl))
                {
                    var key = "";
                    var values = queryValue.Split('&');
                    foreach (var item in values)
                    {
                        var keyValue = item.Split('=');
                        if (keyValue[0] == "key")
                        {
                            key = keyValue[1];
                            break;
                        }
                    }

                    if (!string.IsNullOrEmpty(key) && key == EncryptHelper.GetEncryptKey(secretUrl))
                    {
                        return;
                    }
                }
            }

            HandleUnauthorizedRequest(actionContext);
        }

        private void HandleUnauthorizedRequest(System.Web.Http.Controllers.HttpActionContext actionContext)
        {
            actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.Unauthorized, "访问未经授权！", "application/json");
        }
    }

2.在需要认证授权后才能访问的Controller中类或ACTION方法上添加上述定义的类BasicAuthorizeAttribute，也可在global文件中将该类添加到全局过滤器中，即可

3.配置配置Basic基础认证

    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            //// Web API 配置和服务
            //// 将 Web API 配置为仅使用不记名令牌身份验证。
            //config.SuppressDefaultHostAuthentication();
            //config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));

            //配置Unity依赖注入容器
            config.DependencyResolver = new UnityResolver(UnityConfig.GetConfiguredContainer());
            //配置Basic基础认证
            config.Filters.Add(new BasicAuthorizeAttribute());
            // Web API 路由
            config.MapHttpAttributeRoutes();
            //1.默认路由
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional },
                constraints: new { id = @"\d*" } //约束，这个表示匹配0个或多个数字
                //constraints: new { id = @"\d+" }  //正则\d+表示匹配一个或多个数字
            );
      }
  }