从文本文件读取并使用Button填充到Listbox

Question

I am trying to create a window program where the program reads from a text file and display the data in a listbox. I have tried the below coding but the problem now is that every time I click on the button, it will append and the data will repeat.

How do I do it so that it reads the file and only include new input data?

private void Button_Click(object sender, RoutedEventArgs e)
{
    using (StreamReader sr = new StreamReader("C:\\Users\\jason\\Desktop\\Outbound.txt"))
    {
        string line;
        // Read and display lines from the file until the end of  
        // the file is reached. 
        while ((line = sr.ReadLine()) != null)
        {
            Listbox1.Items.Add(line);
        }
        sr.Close();
    }
}

Answer 1

The probably most simple way to do what you want is to read all lines from the file into a collection, and then assign that collection to the ItemsSource property of your ListBox:

private void Button_Click(object sender, RoutedEventArgs e)
{
    Listbox1.ItemsSource = File.ReadAllLines(@"C:\Users\jason\Desktop\Outbound.txt");
}

Answer 2

As Clemens said in comment, you can either Listbox1.Items.Clear() or Listbox1.ItemsSource = File.ReadAllLines(@"C:\\Users\\jason\\Desktop\\Outbound.txt");
But this would always replace all your listbox with the file. If you just want, as you said, to enter new data, you could simply check if if(!Listbox1.Items.Contains(line)) before adding the item.
Depends on what you really want, reupdate the whole list or just add new entries and not removing old ones.