How can I save a listbox in a text file

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Good morning!
I have a doubt, I searched a lot but found nothing, I hope someone can help me.
Very well.

I have 2 Forms, on Form1 I have a button and in the Form2 I have a ListBox with data.
What I want is to click the button on Form1 and save the data from the Form2 ListBox in a text file.

The data types that are in the listbox are fairly straightforward, the listbox has at most 12 line, and each row has only one word.

What I have tried:

This is button on Form1

private void toolStripButtonGuardar_Click(object sender, EventArgs e)
        {
            var myForm = new FormVer();

            //Escolher onde salvar o arquivo
            SaveFileDialog sfd = new SaveFileDialog();
            sfd.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
            sfd.Title = "Guardar";
            sfd.Filter = "Arquivos TXT (*.txt)|*.txt";

            if (sfd.ShowDialog() == DialogResult.OK)
            {
                try
                {

                    File.WriteAllLines(sfd.FileName, myForm.listBox.Items.OfType<string>());

                    //Mensagem de confirmação
                    MessageBox.Show("Guardado com sucesso", "Notificação", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "Erro", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
        }

But it doesn't work, always save the file blank.

Posted 5-Aug-17 3:13am

Member 13347457

Updated 11-Aug-17 2:36am

v2

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Alan N 11-Aug-17 8:46am

Why are you creating a new form? You need a reference to the existing FormVer.

1 solution

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Graeme_Grant · Answer 1 · 2017-08-05T03:22:00

C#

File.WriteAllText(sfd.FileName, string.Join("|", myForm.listBox.Items.OfType<string>()));

Update: The above solution is based on the information provided. You imply that the data in the list are simple strings, So the above code joins strings and writes them to disk as a continuous string.

If you are using complex objects like classes, then you need to do more work to serialize the object before you can write it to disk.

Here is a [Newtonsoft] JSON helper for serializing and deserializing:

C#

using Newtonsoft.Json;
using System.Collections.Generic;

namespace DotNet.Shared.Helpers
{
    public static class JsonConverter
    {
        public static string FromClass<T>(T data, bool isEmptyToNull = false, JsonSerializerSettings jsonSettings = null)
        {
            string response = string.Empty;

            if (!EqualityComparer<T>.Default.Equals(data, default(T)))
                response = JsonConvert.SerializeObject(data, jsonSettings);

            return isEmptyToNull ? (response == "{}" ? "null" : response) : response;
        }

        public static T ToClass<T>(string data, JsonSerializerSettings jsonSettings = null)
        {
            var response = default(T);

            if (!string.IsNullOrEmpty(data))
                response = jsonSettings == null
                    ? JsonConvert.DeserializeObject<T>(data)
                    : JsonConvert.DeserializeObject<T>(data, jsonSettings);

            return response;
        }
    }
}

And to use:

C#

File.WriteAllText(sfd.FileName, JsonConverter.FromClass(listBox1.Items.OfType<Person>()));

UPDATE #2: You will always have blank files because of this line:

C#

var myForm = new FormVer();

Instead of creating a new form with empty data, you need to point to the active form with the data. Something like:

C#

var myForm = Application.OpenForms[nameof(FormVer)];