c# - 我怎样才能使这些方法通用？

Question

我有的是一些字典，都是这种类型

Dictionary<Guid, string>

我有很多方法基本上做同样的事情，但使用不同的参数来过滤各种东西。这里有几个示例方法

private IQueryable<SomeClass> FilterContacts(Filter filter,
        IQueryable<SomeClass> query)
    {
        if (filter.Contacts != null && filter.Contacts.Any())
        {
            result = result.Where(x => filter.Contacts.Contains(x.ContactID));
        }

        return result;
    }

private IQueryable<SomeClass> FilterSomethingElse(Filter filter,
        IQueryable<SomeClass> query)
    {
        if (filter.SomethingElse != null && filter.SomethingElse.Any())
        {
            result = result.Where(x => filter.SomethingElse.Contains(x.SomethingElseID));
        }

        return result;
    }

所以它们所有这些方法共享相同的结构，但在过滤器和 where 子句中使用不同的属性。有没有一种方法可以使它足够通用，以至于我只能使用一种方法来做到这一点？

Answer 1

以下解决方案使用委托(delegate)作为参数来注入(inject)一些必要的逻辑，使方法更通用。

private IQueryable<SomeClass> FilterCommon(IQueryable<SomeClass> query
    , Filter filter
    , Func<Filter, Dictionary<Guid, string>> getDictionary
    , Func<SomeClass, Guid> getKey)
{
    IQueryable<SomeClass> result = null;
    Dictionary<Guid, string> commonDictionary = getDictionary(filter);
    if (commonDictionary != null && commonDictionary.Any())
    {
        result = query.Where(x => commonDictionary.ContainsKey(getKey(x)));
    }

    return result;
}

我认为 Filter 参数不是必需的，因此可以简化为:

private IQueryable<SomeClass> FilterCommon(IQueryable<SomeClass> query
    , Dictionary<Guid, string> commonDictionary
    , Func<SomeClass,Guid> getKey)
{
    IQueryable<SomeClass> result = null;
    if (commonDictionary != null && commonDictionary.Any())
    {
        result = query.Where(x => commonDictionary.ContainsKey(getKey(x)));
    }

    return result;
}

用法:

//Initializing a few things first...
Filter myFilter = new Filter();
IQueryable<SomeClass> query = new Queryable();//Just a generated type

//This is for my first example from above
FilterCommon(query, myFilter, x => x.Contacts, x => x.ContactID);

//Second example without filter parameter
FilterCommon(query, myFilter.Contacts, x => x.ContactID);
FilterCommon(query, myFilter.SomethingElse, x => x.SomethingElseID);