使用扩展方法合并。当存在重复的键时，它不会抛出异常，而是用第二个字典中的键替换这些键。

internal static class DictionaryExtensions
{
    public static Dictionary<T1, T2> Merge<T1, T2>(this Dictionary<T1, T2> first, Dictionary<T1, T2> second)
    {
        if (first == null) throw new ArgumentNullException("first");
        if (second == null) throw new ArgumentNullException("second");

        var merged = new Dictionary<T1, T2>();
        first.ToList().ForEach(kv => merged[kv.Key] = kv.Value);
        second.ToList().ForEach(kv => merged[kv.Key] = kv.Value);

        return merged;
    }
}

用法:

Dictionary<string, string> merged = first.Merge(second);

这是我的解决方案:它的行为类似于python中的dict.update()方法。

public static class DictionaryExtensions
{
    public static void Update<K,V>(this IDictionary<K, V> me, IDictionary<K, V> other)
    {
        foreach (var x in other)
        {
            me[x.Key] = x.Value;
        }
    }
}

public static IDictionary<K, V> AddRange<K, V>(this IDictionary<K, V> one, IDictionary<K, V> two)
        {
            foreach (var kvp in two)
            {
                if (one.ContainsKey(kvp.Key))
                    one[kvp.Key] = two[kvp.Key];
                else
                    one.Add(kvp.Key, kvp.Value);
            }
            return one;
        }

Dictionary<String, String> allTables = new Dictionary<String, String>();
allTables = tables1.Union(tables2).ToDictionary(pair => pair.Key, pair => pair.Value);

选项1:这取决于在确定两个字典中都没有重复键的情况下想要发生什么。比你能做的:

var result = dictionary1.Union(dictionary2).ToDictionary(k => k.Key, v => v.Value)

注意:如果在字典中获得任何重复的键，将抛出错误。

选项2:如果你可以有重复的键，那么你必须使用where子句来处理重复的键。

var result = dictionary1.Union(dictionary2.Where(k => !dictionary1.ContainsKey(k.Key))).ToDictionary(k => k.Key, v => v.Value)

注意:它不会得到重复的密钥。如果有任何重复的键，那么它将获得dictionary1的键。

选项3:如果你想使用ToLookup。然后您将得到一个查找，每个键可以有多个值。你可以把这个查找转换成一个字典:

var result = dictionaries.SelectMany(dict => dict)
                         .ToLookup(pair => pair.Key, pair => pair.Value)
                         .ToDictionary(group => group.Key, group => group.First());

其平凡解为:

using System.Collections.Generic;
...
public static Dictionary<TKey, TValue>
    Merge<TKey,TValue>(IEnumerable<Dictionary<TKey, TValue>> dictionaries)
{
    var result = new Dictionary<TKey, TValue>();
    foreach (var dict in dictionaries)
        foreach (var x in dict)
            result[x.Key] = x.Value;
    return result;
}