快速排序c#

public void QuickSort(List<int> arr,int low,int high)
{
if(low>=high)
{
return;
}
int first = low;
int last = high;
int key = arr[low];
while(first<last)
{
while(first<last&&arr[last]>=key)
{
last--;
}
arr[first] = arr[last];
while(first<last&&arr[first]<=key)
{
first++;
}
arr[last] = arr[first];
}
arr[first] = key;
QuickSort(arr, low, first - 1);
QuickSort(arr, first + 1, high);
}