[英]What's the fastest way to copy the values and keys from one dictionary into another in C#?
There doesn't seem to be a dictionary.AddRange() method.似乎没有 dictionary.AddRange() 方法。 Does anyone know a better way to copy the items to another dictionary without using a foreach loop.有谁知道在不使用 foreach 循环的情况下将项目复制到另一个字典的更好方法。
I'm using the System.Collections.Generic.Dictionary.我正在使用 System.Collections.Generic.Dictionary。 This is for .NET 2.0.这适用于 .NET 2.0。
There's the Dictionary
constructor that takes another Dictionary
.有一个Dictionary
构造函数,它接受另一个Dictionary
。
You'll have to cast it IDictionary
, but there is an Add()
overload that takes KeyValuePair<TKey, TValue>
.您必须将其转换为IDictionary
,但有一个Add()
重载需要KeyValuePair<TKey, TValue>
。 You're still using foreach, though.不过,您仍在使用 foreach。
There's nothing wrong with a for/foreach loop. for/foreach 循环没有任何问题。 That's all a hypothetical AddRange method would do anyway.无论如何,这就是一个假设的 AddRange 方法。
The only extra concern I'd have is with memory allocation behaviour, because adding a large number of entries could cause multiple reallocations and re-hashes.我唯一需要担心的是内存分配行为,因为添加大量条目可能会导致多次重新分配和重新散列。 There's no way to increase the capacity of an existing Dictionary by a given amount.没有办法将现有字典的容量增加给定的数量。 You might be better off allocating a new Dictionary with sufficient capacity for both current ones, but you'd still need a loop to load at least one of them.您最好为两个当前字典分配一个具有足够容量的新字典,但您仍然需要一个循环来加载其中至少一个。
var Animal = new Dictionary<string, string>();
可以将现有的动物字典传递给构造函数。
Dictionary<string, string> NewAnimals = new Dictionary<string, string>(Animal);
For fun, I created this extension method to dictionary.为了好玩,我为字典创建了这个扩展方法。 This should do a deep copy wherever possible.这应该尽可能地进行深度复制。
public static Dictionary<TKey, TValue> DeepCopy<TKey,TValue>(this Dictionary<TKey, TValue> dictionary)
{
Dictionary<TKey, TValue> d2 = new Dictionary<TKey, TValue>();
bool keyIsCloneable = default(TKey) is ICloneable;
bool valueIsCloneable = default(TValue) is ICloneable;
foreach (KeyValuePair<TKey, TValue> kvp in dictionary)
{
TKey key = default(TKey);
TValue value = default(TValue);
if (keyIsCloneable)
{
key = (TKey)((ICloneable)(kvp.Key)).Clone();
}
else
{
key = kvp.Key;
}
if (valueIsCloneable)
{
value = (TValue)((ICloneable)(kvp.Value)).Clone();
}
else
{
value = kvp.Value;
}
d2.Add(key, value);
}
return d2;
}
For a primitive type dictionary:对于原始类型字典:
public void runIntDictionary()
{
Dictionary<int, int> myIntegerDict = new Dictionary<int, int>() { { 0, 0 }, { 1, 1 }, { 2, 2 } };
Dictionary<int, int> cloneIntegerDict = new Dictionary<int, int>();
cloneIntegerDict = myIntegerDict.Select(x => x.Key).ToList().ToDictionary<int, int>(x => x, y => myIntegerDict[y]);
}
or with an Object that implement ICloneable:或使用实现 ICloneable 的对象:
public void runObjectDictionary()
{
Dictionary<int, number> myDict = new Dictionary<int, number>() { { 3, new number(3) }, { 4, new number(4) }, { 5, new number(5) } };
Dictionary<int, number> cloneDict = new Dictionary<int, number>();
cloneDict = myDict.Select(x => x.Key).ToList().ToDictionary<int, number>(x => x, y => myDict[y].Clone());
}
public class number : ICloneable
{
public number()
{
}
public number(int newNumber)
{
nr = newnumber;
}
public int nr;
public object Clone()
{
return new number() { nr = nr };
}
public override string ToString()
{
return nr.ToString();
}
}
If you're dealing with two existing objects, you might get some mileage with the CopyTo method: http://msdn.microsoft.com/en-us/library/cc645053.aspx如果您正在处理两个现有对象,则使用 CopyTo 方法可能会有所帮助: http : //msdn.microsoft.com/en-us/library/cc645053.aspx
Use the Add method of the other collection (receiver) to absorb them.使用其他集合(接收器)的 Add 方法来吸收它们。
I don't understand, why not using the Dictionary( Dictionary ) (as suggested by ageektrapped ).我不明白,为什么不使用 Dictionary( Dictionary ) (根据 ageektrapped 的建议)。
Do you want to perform a Shallow Copy or a Deep Copy?您要执行浅拷贝还是深拷贝? (that is, both Dictionaries pointing to the same references or new copies of every object inside the new dictionary?) (也就是说,两个字典都指向新字典中每个对象的相同引用或新副本?)
If you want to create a new Dictionary pointing to new objects, I think that the only way is through a foreach .如果你想创建一个指向新对象的新字典,我认为唯一的方法是通过foreach 。
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