reify，ToString(reify, ToString)

 在您的printStack函数中，您正在清除堆栈。 通过循环并弹出每个项目。 
 
 请参阅此处如何打印堆栈项目而不会弹出它们。 
 
 在C＃中，Stack参数将是一个引用类型，因此在函数中修改它将改变原始Stack。 但是，当Stack实现IEnumerable时，您可以枚举项而不修改原始项。 
 
 你可以使用这样的东西 
 
public static string printStack(IEnumerable<string> stack)
{
    string DisplayOutTxt = "";

    foreach (var obj in stack)
    {
        DisplayOutTxt += obj;
    }

    return DisplayOutTxt;
}
 
 但要做得更容易 
 
returnStack = string.Join("", stack);

In your printStack function you are clearing the stack. By looping through and popping each item. 
 
Refer to here how you can print your stack items without popping them.
 
In C# the Stack parameter will be a reference type, so modifying it in a function will mutate the original Stack. But, as the Stack implements IEnumerable, you can enumerate the items without modifying the original.
 
You could use something like this 
 
public static string printStack(IEnumerable<string> stack)
{
    string DisplayOutTxt = "";

    foreach (var obj in stack)
    {
        DisplayOutTxt += obj;
    }

    return DisplayOutTxt;
}
 
But far more easier would be to do
 
returnStack = string.Join("", stack);