How to Delete Text File Content in C#

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.

// Declare the File Information
FileInfo file = new FileInfo(@ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt");
// write the line using streamwriter
using(StreamWriter sw = file.AppendText()) {
sw.WriteLine(textBox1.Text);
}
// Read the content using Streamreader from text file
using(StreamReader sr = file.OpenText()) {
string s = "";
while ((s = sr.ReadLine()) != null) {
listBox1.Text = s; // Display the text file content to the list box
}
sr.Close();
}

Delete the line from the text file

Write the code given below at the Delete button click event hander.

string path = @ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt";
string word = Convert.ToString(listBox1.SelectedItem); // delete the selected line
var oldLines = System.IO.File.ReadAllLines(path);
var newLines = oldLines.Where(line => !line.Contains(word));
System.IO.File.WriteAllLines(path, newLines);
FileStream obj = new FileStream(path, FileMode.Append);
obj.Close();
// once deleted the selected line and once again read the text file and diplay the new text file in listBox
FileInfo fi = new FileInfo(@ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt");
using(StreamReader sr = fi.OpenText()) {
string s = "";
while ((s = sr.ReadLine()) != null) {
listBox1.Text = s;
}
sr.Close();
}
FileStream obj1 = new FileStream(path, FileMode.Append);
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.

string[] lines = System.IO.File.ReadAllLines(@ "C:\Users\shekhart\documents\visual studio 2013\study\Demo\Demo\Demo.txt");
foreach(string line in lines) // Read all line from the text file
{
listBox1.Items.Add(line);
}

The output looks like the following.

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