比较两个字典并返回差异

Question

我有两个字典，一个包含原始数据，另一个包含新数据。我想比较两个字典并返回一个字典并返回第三个包含更新的字典。

Dictionary<int, Dictionary<string, string>> OriginalDictionary = new Dictionary
{
    {1, new Dictionary<string, string> 
        {{"name", "adam"}, 
         {"age", "15"}
         {"occupation", "student"}},
    {2, new Dictionary<string, string> 
        {{"name", "bob"}, 
         {"age", "40"}
         {"occupation", "doctor"}},
    {3, new Dictionary<string, string> 
        {{"name", "cameron"}, 
         {"age", "32"}
         {"occupation", "teacher"}},
}

Dictionary<int, Dictionary<string, string>> NewDictionary = new Dictionary
{
    {1, new Dictionary<string, string> 
        {{"name", "adam"}, 
         {"age", "15"}
         {"occupation", "student"}},
    {2, new Dictionary<string, string> 
        {{"name", "bob"}, 
         {"age", "40"}
         {"occupation", "lawyer"}}, //this is where it's different
    {3, new Dictionary<string, string> 
        {{"name", "cameron"}, 
         {"age", "32"}
         {"occupation", "teacher"}},
}

我想获取包含更新的第三个字典。它可以是整个第一层，也可以分解成第二层。以下 2 个示例都适用于我。

Dictionary<int, Dictionary<string, string>> UpdateDictionary1 = new Dictionary
{
    {2, new Dictionary<string, string> 
        {{"name", "bob"}, 
         {"age", "40"}
         {"occupation", "lawyer"}} //this is where it's different
}

Dictionary<int, Dictionary<string, string>> UpdateDictionary2 = new Dictionary
{
    {2, new Dictionary<string, string> 
        {{"occupation", "lawyer"}}
}

我已经尝试了这篇帖子How to compare two Dictionaries in C# 的答案，但我为 UpdateDictionary 获得的结果仍然包含来自 NewDictionary 的所有数据。 UpdatesDictionary.Count == 3，我的预期输出应该是UpdatesDictionary.Count == 1。我尝试了Where 答案和Except 答案，但它们都没有按我希望的那样工作。

UpdateDictionary = OriginalDictionary.Where(entry => NewDictionary[entry.Key] != entry.Value).ToDictionary(entry => entry.Key, entry => entry.Value);

UpdateDictionary = OriginalDictionary.Except(NewDictionary).ToDictionary(x => x.Key, x => x.Value);

我还有其他方法可以解决这个问题吗？

谢谢！

Answer 1

首先是简单的部分。查找添加或删除的键：

var addedKeys = NewDictionary.Keys.Except(OriginalDictionary.Keys);
var removedKeys = OriginalDictionary.Keys.Except(NewDictionary.Keys);

接下来，要找到已编辑字典的键，我们将为字典创建一个相等比较器，因为尝试内联所有可能的不同方式会太过分了。

public class DictionaryComparer<TKey, TValue> :
    IEqualityComparer<Dictionary<TKey, TValue>>
{
    private IEqualityComparer<TValue> valueComparer;
    public DictionaryComparer(IEqualityComparer<TValue> valueComparer = null)
    {
        this.valueComparer = valueComparer ?? EqualityComparer<TValue>.Default;
    }
    public bool Equals(Dictionary<TKey, TValue> x, Dictionary<TKey, TValue> y)
    {
        if (x.Count != y.Count)
            return false;
        if (x.Keys.Except(y.Keys).Any())
            return false;
        if (y.Keys.Except(x.Keys).Any())
            return false;
        foreach (var pair in x)
            if (!valueComparer.Equals(pair.Value, y[pair.Key]))
                return false;
        return true;
    }

    public int GetHashCode(Dictionary<TKey, TValue> obj)
    {
        throw new NotImplementedException();
    }
}

现在我们有了这个，调用它非常简单：

var addedKeys = NewDictionary.Keys.Except(OriginalDictionary.Keys);
var removedKeys = OriginalDictionary.Keys.Except(NewDictionary.Keys);
var comparer = new DictionaryComparer<string, string>();
var editedValues = OriginalDictionary.Where(pair =>
    !comparer.Equals(pair.Value, NewDictionary[pair.Key]));