如何在没有魔术字符串的情况下将位置标头设置为WCF 4.0 REST中另

假设我有四个服务,路由注册将更改为使用ServiceRoute的子类,我们稍后在扫描路由表时使用它来“评估”.

using System;
using System.Web;
using System.Web.Routing;

public class Global : HttpApplication
{
    private void Application_Start(object sender,EventArgs e)
    {
        RegisterRoutes();
    }

    private void RegisterRoutes()
    {
        RouteTable.Routes.Add(new ServiceRoute<Service1>("s1"));
        RouteTable.Routes.Add(new ServiceRoute<Service2>("s2"));
        RouteTable.Routes.Add(new ServiceRoute<Service3>("s3"));
        RouteTable.Routes.Add(new ServiceRoute<Service4>("s4"));
    }
}

WorkspaceService.SetLocationHeader现在看起来如下：

private void SetLocationHeader(string id)
{   
    ResourceLinker resourceLinker = new ResourceLinker();

    Uri uri = resourceLinker.GetUri<WorkspaceService>(s => s.Get(id));
    WebOperationContext.Current.OutgoingResponse.SetStatusAsCreated(uri);
}

相同的代码片段可用于从其他服务(例如DocumentService.Get)设置工作空间的uri

[WebGet("{id}")]
public Document Get(string id)
{
    // can be static
    ResourceLinker resourceLinker = new ResourceLinker();

    DocumentEntity entity = _repository.FindById(id);
    Document document = new Document();
    document.Name = entity.Name; 
    // map other properties
    document.Workspace.Name = entity.Workspace.Name;
    document.Workspace.Uri = resourceLinker.GetUri<WorkspaceService>(s => s.Get("0"));
    // map other properties
    return document;
}

使用这种方法没有神奇的字符串,并且不太可能更改方法名称,服务名称,路由表前缀将破坏系统.

以下是从article改编的实施：

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.ServiceModel.Activation;
using System.ServiceModel.Web;
using System.Web.Routing;

public interface IServiceRoute
{
    Type ServiceType
    {
        get;
    }

    string RoutePrefix
    {
        get;
        set;
    }
}

public class ServiceRoute<T> : ServiceRoute,IServiceRoute
{
    public ServiceRoute(string routePrefix) : this(routePrefix,new WebServiceHostFactory())
    {
    }

    public ServiceRoute(string routePrefix,ServiceHostFactoryBase serviceHostFactory)
        : base(routePrefix,serviceHostFactory,typeof (T))
    {
        RoutePrefix = routePrefix;
        ServiceType = typeof (T);
    }

    #region IServiceRoute Members

    public string RoutePrefix
    {
        get;
        set;
    }

    public Type ServiceType
    {
        get;
        private set;
    }

    #endregion
}

public static class RouteTableExtensions
{
    public static void AddService<T>(this RouteCollection routeCollection,string routePrefix)
    {
        routeCollection.Add(new ServiceRoute<T>(routePrefix));
    }

    public static string GetRoutePrefixForType<T>(this RouteCollection routeCollection)
    {
        var routeServiceType = routeCollection
            .OfType<IServiceRoute>()
            .FirstOrDefault(r => r.ServiceType == typeof (T));
        if (routeServiceType != null)
        {
            return routeServiceType.RoutePrefix;
        }
        return null;
    }
}

public interface IResourceLinker
{
    Uri GetUri<T>(Expression<Action<T>> restMethod);
}

public class ResourceLinker : IResourceLinker
{
    private readonly Uri _baseUri;

    public ResourceLinker()
        : this("http://localhost:53865")
    {
    }

    public ResourceLinker(string baseUri)
    {
        _baseUri = new Uri(baseUri,UriKind.Absolute);
    }

    #region IResourceLinker Members

    public Uri GetUri<T>(Expression<Action<T>> restMethod)
    {
        var methodCallExpression = (MethodCallExpression) restMethod.Body;
        var uriTemplateForMethod = GetUriTemplateForMethod(methodCallExpression.Method);

        var args = methodCallExpression.Method
            .GetParameters()
            .Where(p => uriTemplateForMethod.Contains("{" + p.Name + "}"))
            .ToDictionary(p => p.Name,p => ValuateExpression(methodCallExpression,p));

        var prefix = RouteTable.Routes.GetRoutePrefixForType<T>();
        var newBaseUri = new Uri(_baseUri,prefix);
        var uriMethod = new UriTemplate(uriTemplateForMethod,true);
        return uriMethod.BindByName(newBaseUri,args);
    }

    #endregion

    private static string ValuateExpression(MethodCallExpression methodCallExpression,ParameterInfo p)
    {
        var argument = methodCallExpression.Arguments[p.Position];
        var constantExpression = argument as ConstantExpression;
        if (constantExpression != null)
        {
            return constantExpression.Value.ToString();
        }

        //var memberExpression = (argument as MemberExpression);
        var lambdaExpression = Expression.Lambda(argument,Enumerable.Empty<ParameterExpression>());
        var result = lambdaExpression.Compile().DynamicInvoke().ToString();
        return result;
    }

    private static string GetUriTemplateForMethod(MethodInfo method)
    {
        var webGet = method.GetCustomAttributes(true).OfType<WebGetAttribute>().FirstOrDefault();
        if (webGet != null)
        {
            return webGet.UriTemplate ?? method.Name;
        }

        var webInvoke = method.GetCustomAttributes(true).OfType<WebInvokeAttribute>().FirstOrDefault();
        if (webInvoke != null)
        {
            return webInvoke.UriTemplate ?? method.Name;
        }

        throw new InvalidOperationException(string.Format("The method {0} is not a web method.",method.Name));
    }
}

ResourceLinker的默认构造函数需要进行一些更改以获取Web应用程序的基本uri,同时考虑到HTTPS可能会在负载均衡器处终止.这不属于这个答案.