我该如何修补与可枚举System.Web.Http.OData.Delta？ [英] How do I patch enumerables with System.Web.Http.OData.Delta?

问题描述

试图使用的 System.Web.Http.OData.Delta 实施 PATCH 中的ASP.NET Web API服务的方法，但似乎无法更改应用到类型的属性的IEnumerable＆LT; T＆GT; 。我使用的是三角洲（2012.2-RC-76 g8a73abe）最新的Git版本。任何人都已经能够使这项工作？

Trying to make use of System.Web.Http.OData.Delta to implement PATCH methods in ASP.NET Web API services, but it seems unable to apply changes to properties of type IEnumerable<T>. I'm using the latest Git revision of Delta (2012.2-rc-76-g8a73abe). Has anyone been able to make this work?

考虑这个数据类型，它应该有可能在一个PATCH请求到Web API服务来更新

Consider this data type, which it should be possible to update in a PATCH request to the Web API service:

public class Person
{
    HashSet<int> _friends = new HashSet<int>();

    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public IEnumerable<int> Friends
    {
        get { return _friends; }
        set
        {
            _friends = value != null ? new HashSet<int>(value) : new HashSet<int>();
        }
    }

    public Person(int id, string firstName, string lastName)
    {
        Id = id;
        FirstName = firstName;
        LastName = lastName;
    }

    public Person()
    {
    }
}

本网页API方法实现了人的修补三角洲＆LT;＆人GT; ：

public void Patch(int id, Delta<Person> delta)
{
    var person = _persons.Single(p => p.Id == id);
    delta.Patch(person);
}

如果我返回以下JSON补丁请求到服务，人的朋友属性应被更新，但可惜它不会发生：

If I send a PATCH request with the following JSON to the service, the person's Friends property should be updated, but alas it doesn't happen:

{"Friends": [1]}

而问题的关键是如何真正使增量更新朋友与此数据。又见讨论在codePLEX 。

推荐答案

的问题可能是，德塔会尝试分配JSON的 JArray 你的 HashSet的＆LT; INT＆GT;

The problem likely is that Deta will try to assign JSON's JArray to your Hashset<int>

如果您正在使用它对抗JsonMEdiaTypeFormatter你内在三角洲code（这意味着你可以修改它），你必须做这样的事情（这是粗糙的，但工程）：

If you are using it against JsonMEdiaTypeFormatter and you internalized the Delta code (meaning you can modify it), you'd have to do something like this (this is rough, but works):

里面， BOOL TrySetPropertyValue（字符串名称，对象的值） 三角洲＆LT; T＆GT; ，它返回false

Inside, bool TrySetPropertyValue(string name, object value) of Delta<T>, where it returns false:

        if (value != null && !cacheHit.Property.PropertyType.IsPrimitive && !isGuid && !cacheHit.Property.PropertyType.IsAssignableFrom(value.GetType()))
        {
           return false;
        }

更改为：

var valueType = value.GetType();
var propertyType = cacheHit.Property.PropertyType;
if (value != null && !propertyType.IsPrimitive && !propertyType.IsAssignableFrom(valueType))
{
    var array = value as JArray;
    if (array == null)
        return false;

    var underlyingType = propertyType.GetGenericArguments().FirstOrDefault() ??
        propertyType.GetElementType();
    if (underlyingType == typeof(string))
    {
        var a = array.ToObject<IEnumerable<string>>();
        value = Activator.CreateInstance(propertyType, a);
    }
    else if (underlyingType == typeof(int))
    {
        var a = array.ToObject<IEnumerable<int>>();
        value = Activator.CreateInstance(propertyType, a);
    }
    else
        return false;
}

这将只与 INT 或字符串收藏工作，但希望能轻推你进入一个很好的方向。

This will only work with collections of int or string but hopefully nudges you into a good direction.

例如，现在你的模型有：

For example, now your model can have:

public class Team {
        public HashSet<string> PlayerIds { get; set; }
        public List<int> CoachIds { get; set; }
    }

和你能够成功地更新它们。

And you'd be able to successfully update them.

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