ASP.NET Web API为单个路由定制IHttpControllerSelector

我需要一个自定义的IHttpControllerSelector,它只应用于特定的路由.所有其他Web api路由应使用IHttpControllerSelector的默认实现.

在研究时我发现以下代码意味着在应用程序启动时替换IHttpControllerSelector,但它完全替换了默认的控制器选择器,这导致应用程序中的所有路由都使用我的自定义控制器选择器：

config.Services.Replace(typeof(IHttpControllerSelector),new CustomControllerSelector(config));

有没有办法为单个路由配置IHttpControllerSelector？

解决方法

然后只需使CustomControllerSelector继承自DefaultHttpControllerSelector并检查该标志：

>如果已设置,请继续使用自定义逻辑
>如果未设置,则返回base(DefaultHttpControllerSelector)

这是代码：

1)消息处理程序,设置标志

public class RouteSpecificHandler : DelegatingHandler
{
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,CancellationToken cancellationToken)
    {
        request.Properties["UseCustomSelector"] = true;
        return base.SendAsync(request,cancellationToken);
    }
}

2)仅将每个路由消息处理程序分配给特定路由(不要为其他路由运行)

config.Routes.MapHttpRoute(
            name: "MyRoute",routeTemplate: "api/dummy/{id}",defaults: new {controller = "Dummy",id = RouteParameter.Optional},constraints: null,handler: new RouteSpecificHandler { InnerHandler = new HttpControllerDispatcher(config) }
            );

3)尊重旗帜的自定义选择器：

public class CustomSelector : DefaultHttpControllerSelector
{
    public CustomSelector(HttpConfiguration configuration) : base(configuration)
    {
    }

    public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
    {
        if (request.Properties.ContainsKey("UseCustomSelector") &&
            request.Properties["UseCustomSelector"] as bool? == true)
        {
            //your logic goes here
        }

        return base.SelectController(request);
    }
}

4)注册选择器：

config.Services.Replace(typeof(IHttpControllerSelector),new CustomSelector(config));

编辑

如果你不希望从DefaultHttpControllerSelector继承 – 那么直接实现IHttpControllerSelector,而不是调用base.SelectController(request)将旧选择器保存为类中的字段/属性

public class CustomSelector : IHttpControllerSelector
{
    private HttpConfiguration _config;

    public IHttpControllerSelector PreviousSelector {get; set;}

    public CustomSelector(HttpConfiguration configuration)
    {
         _config = configuration;
    }

    public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
    {
        if (request.Properties.ContainsKey("UseCustomSelector") &&
            request.Properties["UseCustomSelector"] as bool? == true)
        {
            //your logic goes here
        }

        return PreviousSelector.SelectController(request);
    }
}

然后只需更改注册：

var previousSelector = config.Services.GetService(typeof(IHttpControllerSelector)) as IHttpControllerSelector;
 config.Services.Replace(typeof(IHttpControllerSelector),new CustomSelector(config) { PreviousSelector = previousSelector});

（编辑：安卓应用网）

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