How to open text in Notepad from .NET?

When I click a button on a Windows Forms form, I would like to open a Notepad window containing the text from a TextBox control on the form.

How ca开发者_C百科n I do that?

You don't need to create file with this string. You can use P/Invoke to solve your problem.

Usage of NotepadHelper class:

NotepadHelper.ShowMessage("My message...", "My Title");

NotepadHelper class code:

using System;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace Notepad
{
    public static class NotepadHelper
    {
        [DllImport("user32.dll", EntryPoint = "SetWindowText")]
        private static extern int SetWindowText(IntPtr hWnd, string text);

        [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
        private static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

        [DllImport("User32.dll", EntryPoint = "SendMessage")]
        private static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);

        public static void ShowMessage(string message = null, string title = null)
        {
            Process notepad = Process.Start(new ProcessStartInfo("notepad.exe"));
            if (notepad != null)
            {
                notepad.WaitForInputIdle();

                if (!string.IsNullOrEmpty(title))
                    SetWindowText(notepad.MainWindowHandle, title);

                if (!string.IsNullOrEmpty(message))
                {
                    IntPtr child = FindWindowEx(notepad.MainWindowHandle, new IntPtr(0), "Edit", null);
                    SendMessage(child, 0x000C, 0, message);
                }
            }
        }
    }
}

References (pinvoke.net and msdn.microsoft.com):

SetWindowText: pinvoke | msdn

FindWindowEx: pinvoke | msdn

SendMessage: pinvoke | msdn

Try this out:

System.IO.File.WriteAllText(@"C:\test.txt", textBox.Text);
System.Diagnostics.Process.Start(@"C:\test.txt");

Save the file to disk using File.WriteAllText:

File.WriteAllText("path to text file", myTextBox.Text);

Then use Process.Start to open it in notepad:

Process.Start("path to notepad.exe", "path to text file");

For non ASCII user.

[DllImport("User32.dll", EntryPoint = "SendMessage", CharSet = CharSet.Unicode)]
private static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);

Based on @Peter Mortensen answer

Add CharSet = CharSet.Unicode to the attribute for supporting Unicode characters

I was using the NotepadHelper solution until I discovered it doesn't work on Windows 11. Writing the file to disk and starting with the default text editor seems to be the best solution. This has already been posted, but I discovered you need to pass UseShellExecute=true.

System.IO.File.WriteAllText(path, value);
System.Diagnostics.ProcessStartInfo psi = new() { FileName = path, UseShellExecute = true };
System.Diagnostics.Process.Start(psi);

I write to the System.IO.Path.GetTempPath() folder and run a cleanup when the application exits - searching for a unique prefix pattern for file names used by my app. Something like this:

string pattern = TempFilePrefix + "*.txt";
foreach (string f in Directory.EnumerateFiles(Path.GetTempPath(), pattern))
{
    File.Delete(f);
}