Display All Lines of Text ( Notepad ) File in TextBox using C#

Try this

Html Code

<div>
        <asp:TextBox ID="txtFile1" runat="server"></asp:TextBox>        
    </div>

Code

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            string ss = string.Empty;
            int count = default(int);
            string fileString = File.ReadAllText(@"F:\Users\ashutosh\Desktop\Test Details.txt");
            Dictionary<string, int> fileStringDictionary = new Dictionary<string, int>();
            string[] splittedFileString = fileString.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
            foreach (string word in splittedFileString)
            {
                if (fileStringDictionary.ContainsKey(word))
                    fileStringDictionary[word]++;
                else
                {
                    count++;
                    fileStringDictionary.Add(word, count);
                }
            }
            foreach (KeyValuePair<string, int> pair in fileStringDictionary)
            {
                ss += pair.Key + " ";
            }
            this.txtFile1.Text = ss;
        }
    }

Namespaces

using System;
using System.Collections.Generic;
using System.IO;