Call List from Class

Question

Test, call Data1 from Class "Check_" and show in listbox1.

Class;

using System;  
using System.Collections.Generic;  
using System.IO;  
using System.Linq;  
using System.Text;  
using System.Threading.Tasks;  
  
namespace Str3Number_1  
{  
    public class Check_  
    {  
        private List<string> Data1 = new List<string>();  
  
  
        public void FileOperations()  
        {  
            foreach (var s in File.ReadLines(@"C:\Users\family\Documents\3digit.txt"))  
            {  
                Data1.Add(s);  
            }  
              
        }  
  
  
    }  
}  

Form1;

using System;  
using System.Collections.Generic;  
using System.ComponentModel;  
using System.Data;  
using System.Drawing;  
using System.IO;  
using System.Linq;  
using System.Text;  
using System.Threading.Tasks;  
using System.Windows.Forms;  
  
namespace Str3Number_1  
{  
    public partial class Form1 : Form  
    {  
        Check_ Result_ = new Check_();  
  
        public Form1()  
        {  
            InitializeComponent();  
        }  
  
        private void Form1_Load(object sender, EventArgs e)  
        {  
        }  
        public void viewAllData()  
        {  
            var lst = Result_.FileOperations();  
            listBox1.Items.Add(lst);  
        }  
        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)  
        {  
            viewAllData();  
  
        }  
  
        private void button1_Click(object sender, EventArgs e)  
        {  
  
        }  
  
    }  
}  

Answer 1

Unsure what the issue is but perhaps this might help, two choices to read lines from a file.

using System.Collections.Generic;  
using System.IO;  
using System.Linq;  
  
namespace YieldReadFileFormDemo  
{  
    public class FileOperations  
    {  
        public static IEnumerable<string> ReadYield(string fileName)  
        {  
            var lines = File.ReadAllLines(fileName);  
  
            foreach (var line in lines)  
            {  
                yield return line;  
            }  
        }  
  
        public static List<string> Read(string fileName)   
            => File.ReadAllLines(fileName).ToList();  
    }  
}  

Usage

using System;  
using System.Windows.Forms;  
  
namespace YieldReadFileFormDemo  
{  
    public partial class Form1 : Form  
    {  
        public Form1()  
        {  
            InitializeComponent();  
        }  
  
        private void YieldButton_Click(object sender, EventArgs e)  
        {  
            foreach (var item in FileOperations.ReadYield("TextFile1.txt"))  
            {  
                listBox1.Items.Add(item);  
            }  
        }  
  
        private void ExpressionButton_Click(object sender, EventArgs e)  
        {  
            listBox2.DataSource = FileOperations.Read("TextFile1.txt");  
        }  
    }  
}