如何将用户输入存储到列表中然后输出结果-C＃控制台程序

Question

How do I store user input into a "List" List<string> ItemList then output whatever was entered?

Currently, when I run the program users can enter values into the varItemInput and the for-loop proceeds until 10 entries have been input, but then instead of outputting the entered values, it outputs 10 empty list values. What am I doing wrong?

I think the error is, it's not storing the users input into varItemInput and is just outputting the predefined empty List.Add(""); values.

How would I make a user populated List up to 10 entries?

This is supposed to be like an "Inventory Program" where a user enters an item like a Hammer, then after 10 entries it displays all 10 entries on the output screen.

I know how to do this with an array, but this particular program has to be done with a List.

Here is my code

using System;
using System.Collections.Generic;

namespace ListProgram
{
    class Program
    {
        static void Main(string[] args)
        {
            string varListInput = null;
            Boolean varIsValid = true;
            Int32 intTime = 3000000;



            while (varIsValid)
            {
                try
                {
                    Console.Clear(); //Clear the console program from any scren values
                    Console.WriteLine("Welcome to OTC CIS120" + "\n");
                    Console.WriteLine("ACME Co. Item Locator List Program" + "\n"); //Header     



                List<string> ItemList = new List<string>();
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");
                ItemList.Add("");

                // Reverse the output to show recent input first.
                ItemList.Reverse();

                for (int i = 0; i < ItemList.Count; i++) // Continue For Loop until i is > List amount.
                {
                    Console.WriteLine(i + ": "+ "Enter Item Name To Add To Inventory"); // Asks for user input into array.
                    varListInput = Console.ReadLine(); // User inputs value into field.

                }

                Console.WriteLine("Items Added To Inventory Are: "); // Outputs List in reverse order. (Recent input first).
                for (int i = 0; i < ItemList.Count; i++)
                {
                    Console.WriteLine(i + ": " + varListInput); // The entered values array output.
                }

                System.Threading.Thread.Sleep(intTime);
            }

            catch (Exception e)
            {
                Console.WriteLine("The Program Has an Error: " + e.Message); // Error message if program encountered an error durring runtime.
                varIsValid = false;
                System.Threading.Thread.Sleep(intTime);
                Environment.Exit(0); //Exit the program
            }
        }
    }
}

}

Answer 1

You don't need to reserve List items for this, for example if you need to add only 10 items:

List<string> ItemList = new List<string>();
Console.WriteLine("Items Added To Inventory Are: "); // Outputs List in reverse order. (Recent input first).
for (int i = 0; i < 10; i++) // Continue For Loop until i is < the needed amount.
{
    Console.WriteLine($"{i+1}: Enter Item Name To Add To Inventory"); // Asks for user input into array.
    var ListInput = Console.ReadLine(); // User inputs value into field.
    ItemList.Add(ListInput);
}

However to replace the value of a list item you can just assign the new value like:

ItemList[i] = newStringValue;

Answer 2

In your original post you aren't getting the current item from the list. You are just showing the last item entered. If I understand your problem correctly, this should work.

using System;
using System.Collections.Generic;

namespace ListProgram
{
 class Program
 {
    static void Main(string[] args)
    {
        string varListInput = null;
        Boolean varIsValid = true;
        Int32 intTime = 3000000;

        while (varIsValid) //don't really understand why you need/have this while loop, but not the question
        {
            try
            {
                Console.Clear();
                Console.WriteLine("Welcome to OTC CIS120"); //you're already using WriteLine, you don't need to append \n
                Console.WriteLine("ACME Co. Item Locator List Program");
                Console.WriteLine(); //for one line spacing between header and user input

                var ItemList = new List<string>();

                for (int i = 0; i < 10; i++) // Continue For Loop until i is > List amount.
                {
                    Console.WriteLine($"{i + 1}: Enter Item Name To Add To Inventory");
                    varListInput = Console.ReadLine(); // User inputs value into field.
                    ItemList.Add(varListInput);
                }

                Console.WriteLine("Items Added To Inventory Are: ");
                //just personal perfence to do it this way rather than list.reverse()
                //item count is 10, but the highest index is only 9.
                for (int i = (ItemList.Count - 1); i >=0; i--)
                {
                    var item = ItemList[i];//need to get the current item from the list
                    Console.WriteLine($"{i +  1}: {item}");
                }

                System.Threading.Thread.Sleep(intTime);//please do NOT EVER use Thread.Sleep in production code
            }

            catch (Exception e)//since Console.ReadLine returns a string I'm not sure what errors this code would produce, therefore when it would stop.
            {
                Console.WriteLine("The Program Has an Error: " + e.Message);
                varIsValid = false;
                System.Threading.Thread.Sleep(intTime);
                Environment.Exit(0); //Exit the program
            }
        }
    }
  }
}

and produced this output

Remember that every time the while loop starts over the item list is cleared and nothing will be retained between runs.

Edit 1 If you do want to use .Reserve() you don't need the second for loop anymore. You could do something like this in between

Console.WriteLine("Items Added To Inventory Are: ");

    ItemList.Reverse();
    ItemList.ForEach(i => Console.WriteLine(i));

and

Thread.Sleep(...)

Edit 2 Using .Reverse() and a second loop (either .ForEach or for (...)) is going to be worse performing than my original single for loop that starts at the end, but you will only notice it on VERY large lists or in loops that do a lot of computations.