在c#中合并2个或更多字典(Dictionary<TKey, TValue>)的最佳方法是什么? (像LINQ这样的3.0特性就可以了)。
我正在考虑一个方法签名，如下所示:
public static Dictionary<TKey,TValue>
Merge<TKey,TValue>(Dictionary<TKey,TValue>[] dictionaries);
or
public static Dictionary<TKey,TValue>
Merge<TKey,TValue>(IEnumerable<Dictionary<TKey,TValue>> dictionaries);
关于重复键的处理:在发生冲突的情况下，保存到字典中的值并不重要，只要它是一致的。
当前回答
注意，如果你使用一个名为“Add”的扩展方法，你可以使用集合初始化器来组合尽可能多的字典，就像这样:
public static void Add<K, V>(this Dictionary<K, V> d, Dictionary<K, V> other) {
foreach (var kvp in other)
{
if (!d.ContainsKey(kvp.Key))
{
d.Add(kvp.Key, kvp.Value);
}
}
}
var s0 = new Dictionary<string, string> {
{ "A", "X"}
};
var s1 = new Dictionary<string, string> {
{ "A", "X" },
{ "B", "Y" }
};
// Combine as many dictionaries and key pairs as needed
var a = new Dictionary<string, string> {
s0, s1, s0, s1, s1, { "C", "Z" }
};
其他回答
注意，如果你使用一个名为“Add”的扩展方法，你可以使用集合初始化器来组合尽可能多的字典，就像这样:
public static void Add<K, V>(this Dictionary<K, V> d, Dictionary<K, V> other) {
foreach (var kvp in other)
{
if (!d.ContainsKey(kvp.Key))
{
d.Add(kvp.Key, kvp.Value);
}
}
}
var s0 = new Dictionary<string, string> {
{ "A", "X"}
};
var s1 = new Dictionary<string, string> {
{ "A", "X" },
{ "B", "Y" }
};
// Combine as many dictionaries and key pairs as needed
var a = new Dictionary<string, string> {
s0, s1, s0, s1, s1, { "C", "Z" }
};
试试下面的方法
static Dictionary<TKey, TValue>
Merge<TKey, TValue>(this IEnumerable<Dictionary<TKey, TValue>> enumerable)
{
return enumerable.SelectMany(x => x).ToDictionary(x => x.Key, y => y.Value);
}
如何添加一个参数重载?
此外，您应该将它们输入为dictionary以获得最大的灵活性。
public static IDictionary<TKey, TValue> Merge<TKey, TValue>(IEnumerable<IDictionary<TKey, TValue>> dictionaries)
{
// ...
}
public static IDictionary<TKey, TValue> Merge<TKey, TValue>(params IDictionary<TKey, TValue>[] dictionaries)
{
return Merge((IEnumerable<TKey, TValue>) dictionaries);
}
试试
namespace Extensions
{
public static class DictionaryExtensions
{
public static Dictionary<T, Y> MergeWith<T, Y>(this Dictionary<T, Y> dictA,
Dictionary<T, Y> dictB)
{
foreach (var item in dictB)
{
if (dictA.ContainsKey(item.Key))
dictA[item.Key] = item.Value;
else
dictA.Add(item.Key, item.Value);
}
return dictA;
}
}
}
当你想合并两个字典时
var d1 = new Dictionary<string, string>();
var d2 = new Dictionary<string, string>();
d1.MergeWith(d2);
@user166390的回答版本增加了一个IEqualityComparer参数，以允许不区分大小写的键比较。
public static T MergeLeft<T, K, V>(this T me, params Dictionary<K, V>[] others)
where T : Dictionary<K, V>, new()
{
return me.MergeLeft(me.Comparer, others);
}
public static T MergeLeft<T, K, V>(this T me, IEqualityComparer<K> comparer, params Dictionary<K, V>[] others)
where T : Dictionary<K, V>, new()
{
T newMap = Activator.CreateInstance(typeof(T), new object[] { comparer }) as T;
foreach (Dictionary<K, V> src in
(new List<Dictionary<K, V>> { me }).Concat(others))
{
// ^-- echk. Not quite there type-system.
foreach (KeyValuePair<K, V> p in src)
{
newMap[p.Key] = p.Value;
}
}
return newMap;
}
