C# List<>与Array性能比较

在.net framework 2.0之前，数组表示可以用Array 和集合类 ArrayList 表示，2.0后，.net 引进了泛型的概念List<>，那么我们的选择就多了一种。

2.0引进泛型其本意是减少类型的装箱拆箱所带来的性能消耗。

比如;

private void CompareTo<T>(List<T> list)

{

....

}

这里的List<T>就是泛型，调用时我不知道要传入什么类型，有可能是int,string或class.

今天主要讨论的是在类型确定的情况下，哪种性能高一些，ArrayList就不用考虑了，它肯定是最慢的，它只能add object type的.这里主要讨论List<>和Array的性能：

先看string的情况：

static void Main(string[] args)
{
const int COUNT=1000;
string[] array = new string[COUNT];
List<string> list = new List<string>();
Console.WriteLine("the count is:{0}",COUNT);

Console.Write("the value of Total for array:");
Stopwatch stopWatch = new Stopwatch();
stopWatch.Start();

for (int i = 0; i < COUNT; i++)
{
array[i] = i.ToString(); ;
}

int theArrayTotal = 0;
for (int i = 0; i < COUNT; i++)
{
//theArrayTotal += array[i];

}
stopWatch.Stop();
Console.Write(theArrayTotal);
Console.WriteLine();
Console.Write("array init time:");

Console.Write(stopWatch.ElapsedMilliseconds.ToString());
stopWatch.Reset();
stopWatch.Start();
Console.WriteLine();

for (int i = 0; i < COUNT; i++)
{
list.Add(i.ToString()) ;
}
int theListTotal = 0;
foreach (string v in list)
{
//theListTotal += v;
}
stopWatch.Stop();
Console.WriteLine("the value of Total for list:{0}", theListTotal);
Console.Write("list init time:");
Console.Write(stopWatch.ElapsedMilliseconds.ToString());
stopWatch.Reset();
Console.Read();

}

当COUNT=1000时，两者看不出差别，用的time都是0

当COUNT=10000时，也没什么区别

当COUNT=100000时，

the count is:100000
the value of Total for array:0
array init time:16
the value of Total for list:0
list init time:21

Aarry 比List快了5

当COUNT=1000000时

the count is:1000000
the value of Total for array:0
array init time:296
the value of Total for list:0
list init time:320

Arry比List快了24

当string时，Arry是要比List快

当用int类时：

static void Main(string[] args)
{
const int COUNT=100000;
int[] array = new int[COUNT];
List<int> list = new List<int>();
Console.WriteLine("the count is:{0}",COUNT);

Console.Write("the value of Total for array:");
Stopwatch stopWatch = new Stopwatch();
stopWatch.Start();

for (int i = 0; i < COUNT; i++)
{
array[i] = i;
}

int theArrayTotal = 0;
for (int i = 0; i < COUNT; i++)
{
//theArrayTotal += array[i];

}
stopWatch.Stop();
Console.Write(theArrayTotal);
Console.WriteLine();
Console.Write("array init time:");

Console.Write(stopWatch.ElapsedMilliseconds.ToString());
stopWatch.Reset();
stopWatch.Start();
Console.WriteLine();

for (int i = 0; i < COUNT; i++)
{
list.Add(i) ;
}
int theListTotal = 0;
foreach (int v in list)
{
//theListTotal += v;
}
stopWatch.Stop();
Console.WriteLine("the value of Total for list:{0}", theListTotal);
Console.Write("list init time:");
Console.Write(stopWatch.ElapsedMilliseconds.ToString());
stopWatch.Reset();
Console.Read();
}

修改COUNT=1000,10000,100000,1000000依次输入为：

the count is:1000
the value of Total for array:0
array init time:0
the value of Total for list:0
list init time:0

the count is:10000
the value of Total for array:0
array init time:0
the value of Total for list:0
list init time:0

the count is:100000
the value of Total for array:0
array init time:0
the value of Total for list:0
list init time:1

the count is:1000000
the value of Total for array:0
array init time:7
the value of Total for list:0
list init time:17

the count is:10000000
the value of Total for array:0
array init time:77
the value of Total for list:0
list init time:218

（不同的硬件配置会有不同的结果）

从上面的结果来看array的效率要比List的要高一些，当数组长度不是很大时，两者没什么区别，建议用List<>，毕竟是可变长度，可以Add;特殊应用还是建议用array，

不提倡用ArrayList.