C# List 根据对象属性去重的四种方法对比

private void testdistinct()
{
    task.run(() =>
    {
        //生成测试数据
        datetime dt = datetime.now;
        random rnd = new random();
        list<mydata> list = new list<mydata>();
        int total = 1000000;
        for (int i = 0; i < total; i++)
        {
            mydata info = new mydata();
            info.id = rnd.next(1, total * 10).tostring();
            info.name = rnd.next(1, total * 10).tostring();
            list.add(info);
        }
        double d = datetime.now.subtract(dt).totalmilliseconds;

        //方法一
        datetime dt1 = datetime.now;
        dictionary<string, mydata> result1 = new dictionary<string, mydata>();
        foreach (mydata item in list)
        {
            mydata temp;
            if (!result1.trygetvalue(item.name, out temp))
            {
                result1.add(item.name, item);
            }
        }
        list<mydata> r1 = result1.values.tolist();
        double d1 = datetime.now.subtract(dt1).totalmilliseconds;

        //方法二
        datetime dt2 = datetime.now;
        list<mydata> result2 = list.tolookup(item => item.name).todictionary(item => item.key, item => item.first()).values.tolist();
        double d2 = datetime.now.subtract(dt2).totalmilliseconds;

        //方法三
        datetime dt3 = datetime.now;
        list<mydata> result3 = list.distinct(new mycompare()).tolist();
        double d3 = datetime.now.subtract(dt3).totalmilliseconds;

        //方法四
        datetime dt4 = datetime.now;
        list<mydata> result4 = list.groupby(item => item.name).select(item => item.first()).tolist();
        double d4 = datetime.now.subtract(dt4).totalmilliseconds;

        this.begininvoke(new action(() =>
        {
            textbox1.text = "";
            textbox1.text += "生成 " + list.count.tostring("# ####") + " 条测试数据耗时：" + d + "毫秒\r\n\r\n";
            textbox1.text += "使用方法一去重耗时：" + d1 + "毫秒\r\n\r\n";
            textbox1.text += "使用tolookup和todictionary去重耗时：" + d2 + "毫秒\r\n\r\n";
            textbox1.text += "使用distinct去重耗时：" + d3 + "毫秒\r\n\r\n";
            textbox1.text += "使用groupby和select去重耗时：" + d4 + "毫秒\r\n\r\n";
            textbox1.text += "去重后数量：" + r1.count + "，" + result2.count + "，" + result3.count + "，" + result4.count + "" + "\r\n\r\n";
        }));
    });
}

public class mydata
{
    public string id { get; set; }
    public string name { get; set; }
}

public class mycompare : iequalitycomparer<mydata>
{
    public bool equals(mydata x, mydata y)
    {
        return x.name == y.name;
    }

    public int gethashcode(mydata obj)
    {
        return obj.name.gethashcode();
    }
}