相关疑难解决方法(0)

鉴于以下课程

public class Foo
{
    public int FooId { get; set; }
    public string FooName { get; set; }

    public override bool Equals(object obj)
    {
        Foo fooItem = obj as Foo;

        if (fooItem == null) 
        {
           return false;
        }

        return fooItem.FooId == this.FooId;
    }

    public override int GetHashCode()
    {
        // Which is preferred?

        return base.GetHashCode();

        //return this.FooId.GetHashCode();
    }
}

我已经覆盖了该Equals方法,因为它Foo代表了Foos表的一行.哪个是覆盖的首选方法GetHashCode？

覆盖为什么重要GetHashCode？

这就是我想要做的.我正在使用LINQ to XML查询XML文件,它为我提供了一个IEnumerable <T>对象,其中T是我的"Village"类,填充了此查询的结果.有些结果是重复的,所以我想在IEnumerable对象上执行Distinct(),如下所示:

public IEnumerable<Village> GetAllAlliances()
{
    try
    {
        IEnumerable<Village> alliances =
             from alliance in xmlDoc.Elements("Village")
             where alliance.Element("AllianceName").Value != String.Empty
             orderby alliance.Element("AllianceName").Value
             select new Village
             {
                 AllianceName = alliance.Element("AllianceName").Value
             };

        // TODO: make it work...
        return alliances.Distinct(new AllianceComparer());
    }
    catch (Exception ex)
    {
        throw new Exception("GetAllAlliances", ex);
    }
}

由于默认的比较器不适用于Village对象,我实现了一个自定义的比较器,如AllianceComparer类中所示:

public class AllianceComparer : IEqualityComparer<Village>
{
    #region IEqualityComparer<Village> Members
    bool IEqualityComparer<Village>.Equals(Village x, Village y)
    {
        // Check whether the compared objects reference the same data.
        if (Object.ReferenceEquals(x, y)) …

我有一个LINQ Distinct()语句,它使用我自己的自定义比较器,如下所示:

class MyComparer<T> : IEqualityComparer<T> where T : MyType
{
    public bool Equals(T x, T y)
    {
        return x.Id.Equals(y.Id);
    }

    public int GetHashCode(T obj)
    {
        return obj.Id.GetHashCode();
    }
}

...

var distincts = bundle.GetAllThings.Distinct(new MyComparer<MySubType>());

这一切都很好,花花公子,按我的意愿工作.出于好奇,我是否需要定义自己的Comparer,还是可以用委托替换它？我以为我应该可以这样做:

var distincts = bundle.GetAllThings.Distinct((a,b) => a.Id == b.Id);

但这不编译.有一个巧妙的伎俩吗？

我有2个相同类型的列表.左侧列表:

var leftList = new List<Person>();
leftList.Add(new Person {Id = 1, Name = "John", Changed = false});
leftList.Add(new Person {Id = 2, Name = "Alice", Changed = false});
leftList.Add(new Person {Id = 3, Name = "Mike", Changed = false});

正确的清单:

var rightList = new List<Person>();
rightList.Add(new Person {Id = 1, Name = "John", Changed = false});
rightList.Add(new Person {Id = 3, Name = "Mike", Changed = true});
rightList.Add(new Person {Id = 4, Name = "Joshi", Changed = true}); …

我有以下课程

public class Application
{
    public int Id { get; set; }

    public int Version { get; set; }

    (...)
}

我有以下几点IEnumerable<Application>：

IEnumerable<Application> applications1 = new List<Application>
{
    new Application {Id = 1, Version = 1},
    new Application {Id = 2, Version = 1},
    new Application {Id = 3, Version = 3}
};

IEnumerable<Application> applications2 = new List<Application>
{
    new Application {Id = 1, Version = 2},
    new Application {Id = 3, Version = 2}
    new Application {Id …

我有两个列表对象.我将它们组合成一个列表.虽然合并我需要删除重复.TweetID是要比较的字段.

List<TweetEntity> tweetEntity1 = tt.GetTweetEntity(Convert.ToInt16(pno), qdecoded, longwoeid );
List<TweetEntity> tweetEntity2 = tt.GetTweetEntity(Convert.ToInt16(pno), qdecoded);
List<TweetEntity> tweetEntity = tweetEntity1.Concat(tweetEntity2).ToList(); 

我已将两个列表合并,但无法过滤掉重复项.是否有任何内置函数来删除List <>中的重复项？