如何用另一个数组创建和初始化一个数组?

To create and initialize an array with another array I currently do this:

要创建一个数组并初始化另一个数组，我目前这样做:

void Foo( int[] a )
{
    int[] b = new int[ a.Length ];
    for ( int i = 0; i < a.Length; ++i )
        b[ i ] = a[ i ];

    // Other code ...
}

Is there a shorter or more idiomatic way of doing this in C#?

在c#中是否有更短或更习惯的方法来实现这一点?

It will be great if this can be done in a single statement, like in C++:

如果这可以在一个语句中完成，就像在c++中那样:

vector<int> b( a );

If this cannot be done in a single statement, I will take what I get :-)

如果这不能在一个单独的声明中完成，我将采取我所得到的:-)

4 个解决方案

#1

I like using LINQ for this:

我喜欢用LINQ:

int[] b = a.ToArray();

That being said, Array.Copy does have better performance, if this will be used in a tight loop, etc:

也就是说,数组。拷贝确实有更好的性能，如果这将在一个紧密循环中使用，等等:

int[] b = new int[a.Length];
Array.Copy(a, b, a.Length);

Edit:

编辑:

It will be great if this can be done in a single statement, like in C++:

如果这可以在一个语句中完成，就像在c++中那样:

vector b( a );

向量b(a);

The C# version of this would be:

c#版本是:

List<int> b = new List<int>(a);

List<T> is C#'s equivalent to std::vector<T>. The constructor above works with any IEnumerable<T>, including another List<T>, an array (T[]), etc.

List 是c# 's等价于std::vector 。上面的构造函数适用于任何IEnumerable ，包括另一个列表，一个数组(T[])等。

#2

Use Array.Copy to copy an array

使用数组。复制一个数组

     int[] source = new int[5];
     int[] target = new int[5];
     Array.Copy(source, target, 5);

#3

Also try the default Clone() function which is implemented from the IClonable interface.

还可以尝试从IClonable接口实现的默认克隆()函数。

int[] b = a.Clone() as int[];

#4

Clone() and ToArray() are syntactically nice because you don't need to pre-allocate a destination array, but in terms of performance, Array.Copy() is the fastest method (see caveat below).

Clone()和ToArray()语法上很好，因为您不需要预先分配目标数组，但是就性能而言，array . copy()是最快的方法(请参阅下面的警告)。

The reason for Array.Copy() being so fast is that it doesn't allocate any memory. However, if you require your arrays to be copied to a new region of memory each time, then Array.Copy() is no longer the fastest method.

copy()如此快速的原因是它没有分配任何内存。但是，如果每次都要求将数组复制到内存的新区域，那么Array.Copy()不再是最快的方法。

Here are my performance results:

以下是我的表现结果:

Copy: 0 ms
Copy (with allocation): 449 ms
Clone: 323 ms
ToArray: 344 ms

And here's the code I used:

下面是我使用的代码:

const int arrayLength = 100000;
const int numberCopies = 1000;
var a = new int[arrayLength];
var b = new int[arrayLength];

var stopwatch = new Stopwatch();
for (var i = 0; i < numberCopies; i++) {
    Array.Copy(a, b, arrayLength);
}
Console.WriteLine($"Copy: {stopwatch.ElapsedMilliseconds} ms");

stopwatch.Restart();
for (var i = 0; i < numberCopies; i++) {
    var c = new int[arrayLength];
    Array.Copy(a, c, arrayLength);
}
Console.WriteLine($"Copy (with allocation): {stopwatch.ElapsedMilliseconds} ms");

stopwatch.Restart();
for (var i = 0; i < numberCopies; i++) {
    b = (int[]) a.Clone();
}
Console.WriteLine($"Clone: {stopwatch.ElapsedMilliseconds} ms");

stopwatch.Restart();
for (var i = 0; i < numberCopies; i++) {
    b = a.ToArray();
}
Console.WriteLine($"ToArray: {stopwatch.ElapsedMilliseconds} ms");

#1