我想用一些外部服务器端逻辑对查询结果修改属性。要做到这一点，我需要申请微风查询选项，修改结果集，并返回它。

I want to use some external server-side logic to modify properties on the results of a query. To do this, I'll need to apply the Breeze query options, modify the result set, and return it.

我知道基本上我怎么可以申请 OdataQueryOptions 来我的查询，但我不想错过所有的事情，BreezeJS确实该Web阿比的OData的没有按'吨。例如，我想保持 inlineCount 。

I know essentially how I can apply OdataQueryOptions to my query, but I don't want to miss out on all the things that BreezeJS does that Web Api's OData doesn't. For example, I want to keep inlineCount.

我怎样才能做到这一点？是否有某种方式挂接到微风的查询，修改code？

How can I do this? Is there some way to hook into Breeze's query modifying code?

在情况下它的事项，我使用实体框架6和Web阿比2。

In case it matters, I'm using Entity Framework 6 and Web Api 2.

推荐答案

好吧，我不知道是否有更好的方法（因为这似乎是一个大量的工作，对什么似乎像这将是一个常见的​​情况） ，但这里是我如何解决这一点。

Ok, I'm not sure if there's a better way (because this seems like a lot of work for what seems like it would be a common use case), but here's how I solved this.

我从 QueryHelper 类继承修改 PostExecuteQuery 方法来执行委托。

I inherited from the QueryHelper class to modify the PostExecuteQuery method to execute a delegate.

public class ExtendedQueryHelper : QueryHelper
{
    public ExtendedQueryHelperOptions Options { get; set; }

    public ExtendedQueryHelper(ODataQuerySettings querySettings) : base(querySettings)
    {}

    public override IEnumerable PostExecuteQuery(IEnumerable queryResult)
    {
        if (Options != null && Options.PostExecuteQueryHandler != null)
        {
            return Options.PostExecuteQueryHandler(queryResult);
        }

        return base.PostExecuteQuery(queryResult);
    }
}

该委托是一类被称为定义的 ExtendedQueryHelperOptions

public class ExtendedQueryHelperOptions
{
    private const string EXTENDED_QUERY_HELPER_OPTIONS_KEY = "EXTENDED_QUERY_HELPER_OPTIONS_KEY";
    public delegate IEnumerable PostExecuteQueryDelegate(IEnumerable queryResult);

    public PostExecuteQueryDelegate PostExecuteQueryHandler { get; set; }

    public void InjectIntoRequest(HttpRequestMessage request)
    {
        request.Properties.Add(EXTENDED_QUERY_HELPER_OPTIONS_KEY, this);
    }

    public static ExtendedQueryHelperOptions GetFromRequest(HttpRequestMessage request)
    {
        object options;
        request.Properties.TryGetValue(EXTENDED_QUERY_HELPER_OPTIONS_KEY, out options);

        return (ExtendedQueryHelperOptions)options;
    }
}

为了设置这些选项，我不得不从 BreezeQueryableAttribute 继承并注入这些选项时， QueryHelper 是正在创建：

In order to set these options, I had to inherit from BreezeQueryableAttribute and inject these options when the QueryHelper is being created:

public class ExtendedBreezeQueryableAttribute : BreezeQueryableAttribute
{
    protected HttpRequestMessage Request { get; set; }

    public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
    {
        Request = actionContext.Request;
        base.OnActionExecuting(actionContext);
    }

    protected override QueryHelper NewQueryHelper()
    {
        var queryHelper = new ExtendedQueryHelper(GetODataQuerySettings());
        queryHelper.Options = ExtendedQueryHelperOptions.GetFromRequest(Request);

        return queryHelper;
    }
}

现在我可以注入code要在筛选的结果是这样运行的：

Now I can inject code to be run on the filtered results like this:

[BreezeController]
public class BreezeController : BaseController
{
    //...

    [HttpGet]
    [ExtendedBreezeQueryable]
    public IQueryable<Foo> Foos()
    {
        var options = new ExtendedQueryHelperOptions
        {
            PostExecuteQueryHandler = delegate(IEnumerable results) {
                // This code will be run after the querying has been
                // applied by Breeze
                var foos = results.Cast<Foo>().ToList();

                foreach (var foo in foos)
                {
                    foo.ComputedProperty = ComputeSomething();
                }

                return foos;
            }
        };

        // Inject these options into the Request, so the ExtendedBreezeQueryableAttribute
        // can get to them later
        options.InjectIntoRequest(Request);
        return Db.Foos;
    }
}