从文件加载列表框

Question

This is my first time creating a C# program so I apologize if this question seems basic. I have 3 list boxes on my design form along with 3 buttons I'd like to load a list of item into each text box when I click the corresponding button for the listbox. can someone instruct me on how to do this.

Answer 1

Abbas has given you a sufficient answer, but there are a couple of problems with it, so I thought I would add my own response. The issues:

1. Streams (anything that implements IDisposable ) need to be closed after you're done with them. You can do this by manually calling Dispose() or by wrapping the creation of the object in a using block.
2. You shouldn't add items to the list box one by one like that in case there are a large number of items. This will cause poor performance and the list box will flicker as it updates/redraws after each item is added.

I would do something like this:

using System.IO;
// other includes

public partial class MyForm : Form
{
    public MyForm()
    {
        // you can add the button event 
        // handler in the designer as well
        someButton.Click += someButton_Click;
    }

    private void someButton_Click( object sender, EventArgs e )
    {
        PopulateList( "some file path here" );
    }

    private void PopulateList( string filePath )
    {
        var items = new List<string>();
        using( var stream = File.OpenRead( filePath ) )  // open file
        using( var reader = new TextReader( stream ) )   // read the stream with TextReader
        {
            string line;

            // read until no more lines are present
            while( (line = reader.ReadLine()) != null )
            {
                items.Add( line );
            }
        }

        // add the ListBox items in a bulk update instead of one at a time.
        listBox.AddRange( items );
    }
}

Answer 2

These are the steps to load the textfile in the listbox.

1. Read textfile line by line
2. While reading, populate the listbox

Here's a small example on how to do this:

string line;
var file = new System.IO.StreamReader("C:\\PATH_TO_FILE\\test.txt");
while ((line = file.ReadLine()) != null)
{
    listBox1.Items.Add(line);
}

Answer 3

all you need to do is create an event handler for each button. You can do it by double-clicking the button on the visual-studio designer. Then you'll see the code window with the following new-created

private void button1_Click(object sender, EventArgs e)
{

}

on this method, implement your item loading method and add them to your ListBox.Items. for example:

private void button1_Click(object sender, EventArgs e)
{
string[] allLines = File.ReadAllLines(@"C:\Test.txt"); // reads all lines from text file
listBox1.AddRange(allLines); // Adds an array of objects into the ListBox's Item Collection.
}

Hope it helps and good luck!

Answer 4

try this example , remember to include System.IO;

Using System.IO;

        private void button3_Click(object sender, EventArgs e)
    {
        //Pass the file path and file name to the StreamReader constructor
        StreamReader sr = new StreamReader("youfilePath");
        string line = string.Empty;
        try
        {
            //Read the first line of text
            line = sr.ReadLine();
            //Continue to read until you reach end of file
            while (line != null)
            {
                this.listBox1.Items.Add(line);
                //Read the next line
                line = sr.ReadLine();
            }

            //close the file
            sr.Close();
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message.ToString());
        }
        finally
        {
            //close the file
            sr.Close();
        }
    }

Regards.