List<Dictionary<string,string>> 的 IEqualityComparer 的正确实现

Question

我有两个 List<Dictionary<string,string>> 代表两个表。我想获取这些表中不同的 Dictionary 对象。

我正在尝试使用 except 方法，因为它基本上是做我想做的：它返回差异。但是因为此方法使用默认比较器，所以我创建了自己的 IEqualityComparer 实现。

在下面的示例中它工作得很好，但在现实生活中字典要复杂得多，所以我想知道 - 我的实现是一个好的解决方案还是必须增强？

class Program
{
    static void Main()
    {

        var table1 = new List<Dictionary<string, string>>{
        new Dictionary<string,string>{
        {"md5","0x1234"},
        {"file_name","name1234"},
        {"size","1234"}},

        new Dictionary<string,string>{
        {"md5","0x1234"},
        {"file_name","name1234"},
        {"size","1234"}},
        };

        var table2 = new List<Dictionary<string, string>>{
        new Dictionary<string,string>{
        {"md5","0x1234"},
        {"file_name","name1234"},
        {"size","1234"}},

        new Dictionary<string,string>{
        {"md5","0x5678"},
        {"file_name","name5678"},
        {"size","5678"}}
        };

        var diff = table2.Except(table1, new DictionaryComparer());

        foreach (var item in diff)
        {
            foreach (var value in item)
            {
                Console.WriteLine(value);
            }
            Console.WriteLine("+++++++++++++++++++++");
        }

        Console.ReadKey();
    }

    public class DictionaryComparer : IEqualityComparer<Dictionary<string, string>>
    {
        public bool Equals(Dictionary<string, string> first, Dictionary<string, string> second)
        {
            if (first == second) return true;
            if ((first == null) || (second == null)) return false;
            if (first.Count != second.Count) return false;

            foreach (var k in first.Keys)
                if (!second.ContainsKey(k))
                    return false;

            foreach (var k in first.Keys)
                if (!first[k].Equals(second[k]))
                    return false;

            return true;
        }

        public int GetHashCode(Dictionary<string, string> obj)
        {
            int resultValue = 0;

            if (obj == null)
            {
                return 0;
            }        

            foreach (var item in obj)
            {
                resultValue += (item.Key.Length + item.Value.Length);
            }

            return resultValue;
        }

    }

Answer 1

我认为以下是更清洁的解决方案：

public class DictionaryComparer : IEqualityComparer<KeyValuePair<string, string>>
{
    public bool Equals(KeyValuePair<string, string> x, KeyValuePair<string, string> y)
    {
        return x.Key.Equals(y.Key) 
            && x.Value.Equals(y.Value);
    }

    public int GetHashCode(KeyValuePair<string, string> obj)
    {
        return string.Concat(obj.Key, obj.Value)
            .GetHashCode();
    }
}