How to read text file (*.txt) in C#

How to read text file in C#?

Open Visual Studio, then click New Project, then select Visual C# on the left, then Windows and then select Windows Forms Application. Name your project "ReadTxtFile" and then click OK

Drag and drop the TextBox, Button controls from the Visual Toolbox onto your form designer, then design your form as shown below.

Add a click event handler to the Open button to allow opening a text file and displaying its content in the TextBox control as shown below.

private async void btnOpen_Click(object sender, EventArgs e)
{
    try
    {
        // Open file dialog to select a text file
        using (OpenFileDialog ofd = new OpenFileDialog() { Filter = "Text Documents|*.txt", Multiselect = false, ValidateNames = true })
        {
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                using (StreamReader sr = new StreamReader(ofd.FileName))
                {
                    txtValue.Text = await sr.ReadToEndAsync();
                }
            }
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message, "Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}

StreamReader.ReadToEndAsync is used for non-blocking reading of the file contents. This ensures the UI remains responsive while reading large files.

This is an example of asynchronously reading a text file and displaying its contents in a TextBox in a Windows Forms application.

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