堆栈表示对象的后进先出集合。当您需要对项目进行后进先出的访问时，可以使用它。在列表中添加项目时，称为推送项目，而在删除项目时，则称为弹出项目。 Stack
特性：
- Stack
的容量是Stack 可以容纳的元素数量。将元素添加到Stack 时，容量会根据需要通过重新分配自动增加。 - 如果Count小于堆栈的容量，则Push是O(1)运算。如果需要增加容量以容纳新元素，则Push变为O(n)操作，其中n为Count。 Pop是O(1)运算。
- Stack
接受null作为有效值，并允许重复的元素。
句法：
void Push(object obj);
例子：
// C# code to insert an object
// at the top of the Stack
using System;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Creating a Stack of strings
Stack myStack = new Stack();
// Inserting the elements into the Stack
myStack.Push("one");
// Displaying the count of elements
// contained in the Stack
Console.Write("Total number of elements in the Stack are : ");
Console.WriteLine(myStack.Count);
myStack.Push("two");
// Displaying the count of elements
// contained in the Stack
Console.Write("Total number of elements in the Stack are : ");
Console.WriteLine(myStack.Count);
myStack.Push("three");
// Displaying the count of elements
// contained in the Stack
Console.Write("Total number of elements in the Stack are : ");
Console.WriteLine(myStack.Count);
myStack.Push("four");
// Displaying the count of elements
// contained in the Stack
Console.Write("Total number of elements in the Stack are : ");
Console.WriteLine(myStack.Count);
myStack.Push("five");
// Displaying the count of elements
// contained in the Stack
Console.Write("Total number of elements in the Stack are : ");
Console.WriteLine(myStack.Count);
myStack.Push("six");
// Displaying the count of elements
// contained in the Stack
Console.Write("Total number of elements in the Stack are : ");
Console.WriteLine(myStack.Count);
}
}
输出：
Total number of elements in the Stack are : 1
Total number of elements in the Stack are : 2
Total number of elements in the Stack are : 3
Total number of elements in the Stack are : 4
Total number of elements in the Stack are : 5
Total number of elements in the Stack are : 6
参考：
- https://docs.microsoft.com/zh-cn/dotnet/api/system.collections.generic.stack-1.push?view=netframework-4.7.2