How to take file from button

Question

I made a application with iTextSharp to put numbers on a PDF file. As you will see in the following code, my application just can do this, only if the file is in a specific directory.

So I made an "Other" button where the user can select a file. What I want to do now is, that the chosen file will download the converted PDF.

Code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

namespace NummerierePDF
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            byte[] bytes = File.ReadAllBytes(@"L:\Users\user\Documents\PDFnummerieren\PDF.pdf");
            iTextSharp.text.Font blackFont = FontFactory.GetFont("Arial", 12, iTextSharp.text.Font.NORMAL, BaseColor.BLACK);
            using (MemoryStream stream = new MemoryStream())
            {
                PdfReader reader = new PdfReader(bytes);
                using (PdfStamper stamper = new PdfStamper(reader, stream))
                {
                    int pages = reader.NumberOfPages;
                    for (int i = 1; i <= pages; i++)
                    {
                        ColumnText.ShowTextAligned(stamper.GetOverContent(i), Element.ALIGN_RIGHT, new Phrase(i.ToString(), blackFont), 568f, 15f, 0);
                    }
                }
                bytes = stream.ToArray();
            }
            File.WriteAllBytes(@"L:\Users\user\Documents\PDFnummerieren\PDF1.pdf", bytes);
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            var FD = new System.Windows.Forms.OpenFileDialog();
            if (FD.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
                string fileToOpen = FD.FileName;

                System.IO.FileInfo File = new System.IO.FileInfo(FD.FileName);



                System.IO.StreamReader reader = new System.IO.StreamReader(fileToOpen);

            }
        }
    }
}

So File.WriteAllBytes(@"L:\Users\user\Documents\PDFnummerieren\PDF1.pdf", bytes); can stay because it doesn't matter where the file will be downloaded after it's converted.

But File.ReadAllBytes(@"L:\Users\user\Documents\PDFnummerieren\PDF.pdf"); shouldn't be a specific directory, it should get the chosen file from button3. As you probably noticed I'm new into programming so I thought maybe I could do this: File.ReadAllBytes(fileToOpen); to get the string. Though that doesn't do his job.

Thanks for your time.

Steve · Accepted Answer

If you want to use a variable between methods of the same class then you need to declare a private and non-static class level variable (called also Instance Field). This is visible to every method of the class.

public partial class Form1 : Form
{
    // Here declare a variable visible to all methods inside the class but 
    // not outside the class. Init it with an empty string
    private string theFile = "";

    private void button1_Click(object sender, EventArgs e)
    {
        // When you click the button1 check if the variable 
        // has been set to something in the button3 click event handler
        if(string.IsNullOrEmpty(theFile) || !File.Exists(theFile))
            return;

        // Now you can use it to load the file and continue with the code
        // you have already written
        byte[] bytes = File.ReadAllBytes(theFile);
        ......
        ......
    }

    private void button3_Click(object sender, EventArgs e)
    {
        // The only job of button3 is to select the file to work on
        // as you can see we can use the variable also here
        var FD = new System.Windows.Forms.OpenFileDialog();
        if (FD.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            theFile = FD.FileName;
    }
}

But do you really need a separate button for this? I mean you could put the three lines of code in the button3 directly in at the start of the code in button1 and remove the superfluos (at this point) button3

I suggest you to read some docs on variable's Scope and Lifetime

How to take file from button

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