Today, I am going to show you a small demo of how to read, write and delete the text file content in a Windows Forms ListBox control.
Step1

Create one empty text file and named it as your desired name and add into your project, as shown below.

Step 2

Create a form. In my case, I have added a TextBox, a ListBox, and three Button controls. Double click on buttons to add event handlers for these buttons.
Step3

Add using System.IO; namespace in your C# file.
Now, begin writing code for each button click event handler.
Add the new line to the text file.
ADD button click event handler.
  1. // Declare the File Information
  2. FileInfo file = new FileInfo(@ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt");
  3. // write the line using streamwriter
  4. using(StreamWriter sw = file.AppendText()) {
  5. sw.WriteLine(textBox1.Text);
  6. }
  7. // Read the content using Streamreader from text file
  8. using(StreamReader sr = file.OpenText()) {
  9. string s = "";
  10. while ((s = sr.ReadLine()) != null) {
  11. listBox1.Text = s; // Display the text file content to the list box
  12. }
  13. sr.Close();
  14. }
Delete the line from the text file
Write the code given below at the Delete button click event hander.
  1. string path = @ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt";
  2. string word = Convert.ToString(listBox1.SelectedItem); // delete the selected line
  3. var oldLines = System.IO.File.ReadAllLines(path);
  4. var newLines = oldLines.Where(line => !line.Contains(word));
  5. System.IO.File.WriteAllLines(path, newLines);
  6. FileStream obj = new FileStream(path, FileMode.Append);
  7. obj.Close();
  8. // once deleted the selected line and once again read the text file and diplay the new text file in listBox
  9. FileInfo fi = new FileInfo(@ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt");
  10. using(StreamReader sr = fi.OpenText()) {
  11. string s = "";
  12. while ((s = sr.ReadLine()) != null) {
  13. listBox1.Text = s;
  14. }
  15. sr.Close();
  16. }
  17. FileStream obj1 = new FileStream(path, FileMode.Append);
  18. obj1.Close();
View the entered content from the text file

Now, write code to view the content of the text file in a ListBox. You can also write this code on Window load event handler.
  1. string[] lines = System.IO.File.ReadAllLines(@ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt");
  2. foreach(string line in lines) // Read all line from the text file
  3. {
  4. listBox1.Items.Add(line);
  5. }
The output looks like the following.

Learn more here: Files in C# and .NET.