ASP .NET MVC 4 WebApi:手动处理 OData 查询 [英] ASP .NET MVC 4 WebApi: Manually handle OData queries

问题描述

我有一个使用 ASP .NET MVC 4 提供的 WebAPI 制作的 Web 服务.我知道 WebAPI 工作的层会自动处理 OData 查询(例如 $filter、$top、$skip)，但是如果我想自己处理过滤呢?

I have a Web Service made using the WebAPI provided by ASP .NET MVC 4. I know that the layer on top of which WebAPI works automatically handles OData Queries (such as $filter, $top, $skip), but what if I want to handle the filtering by myself?

我不是简单地从我的数据库返回数据，但我还有另一层它添加了一些属性，进行了一些转换等.所以查询我的所有数据，转换它们并将它们返回到 WebAPI 类以进行 OData 过滤是不够的.这当然非常慢，而且通常是一个糟糕的想法.

I don't simply return data from my database, but I have another layer which adds some properties, makes some conversions etc. So querying ALL of my data, converting them and returning them to the WebAPI class for OData filtering isn't just good enough. It's of course terribly slow, and generally a crappy idea.

那么有没有一种方法可以将 OData 查询参数从我的 WebAPI 入口点传播到我调用以获取和转换数据的函数?

So is there a way to propagate the OData query parameters from my WebAPI entry point to the functions I call to get and convert the data?

例如，对 /api/people?$skip=10&$top=10 的 GET 会在服务器上调用:

For example, a GET to /api/people?$skip=10&$top=10 would call on the server:

public IQueryable<Person> get() {
    return PersonService.get(SomethingAboutCurrentRequest.CurrentOData);
}

在PersonService中:

public IQueryable<Person> getPeople(var ODataQueries) {
    IQueryable<ServerSidePerson> serverPeople = from p in dbContext.ServerSidePerson select p;
    // Make the OData queries
    // Skip
    serverPeople = serverPeople.Skip(ODataQueries.Skip);
    // Take
    serverPeople = serverPeople.Take(ODataQueries.Take);
    // And so on
    // ...

    // Then, convert them
    IQueryable<Person> people = Converter.convertPersonList(serverPeople);
    return people;
}

推荐答案

我刚刚偶然发现了这篇旧帖子，我正在添加这个答案，因为现在自己处理 OData 查询非常容易.举个例子:

I just stumbled across this old post and I'm adding this answer as it's now very easy to handle the OData queries yourself. Here's an example:

[HttpGet]
[ActionName("Example")]
public IEnumerable<Poco> GetExample(ODataQueryOptions<Poco> queryOptions)
{
    var data = new Poco[] { 
        new Poco() { id = 1, name = "one", type = "a" },
        new Poco() { id = 2, name = "two", type = "b" },
        new Poco() { id = 3, name = "three", type = "c" }
    };

    var t = new ODataValidationSettings() { MaxTop = 2 };
    queryOptions.Validate(t);

    //this is the method to filter using the OData framework
    //var s = new ODataQuerySettings() { PageSize = 1 };
    //var results = queryOptions.ApplyTo(data.AsQueryable(), s) as IEnumerable<Poco>;

    //or DIY
    var results = data;
    if (queryOptions.Skip != null) 
        results = results.Skip(queryOptions.Skip.Value);
    if (queryOptions.Top != null)
        results = results.Take(queryOptions.Top.Value);

    return results;
}

public class Poco
{
    public int id { get; set; }
    public string name { get; set; }
    public string type { get; set; }
}

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