Question

I use this code to read every line from my file but it only reads (or it only displays the last line of the file). When i open the file in notepad i can see that there are more than one lines.
Here’s the code that i am using:

 using (StreamReader sr = File.OpenText(newPath))
        {
            String input;
            while ((input = sr.ReadLine()) != null)
            {

                TextBox1.Text = input;  

            }

Answer 1

You need to use:

TextBox1.Text += input;

else the described behaviour is correct

eventually you can change your sample as:

String input;
String target = String.Empty;
try {
using (StreamReader sr = File.OpenText(newPath)) 
{ 
    while ((input = sr.ReadLine()) != null) 
    { 
        target += input;   
    }
}
TextBox1.Text = target;
} catch { ... }

and the best would be to extract the reading process to a separate method..