How to open Notepad from a Windows Forms application and place some text in it?

I'm using VB.NET and Visual Studio 2008.

My question is: How do I open Notepad from a 开发者_运维技巧Windows Forms application, and then place some text string in the Notepad window?

The easiest approach is to write a text-file, then open that, rather than the other way round.

You can use System.File.IO.WriteAllText, and the System.Diagnostics.Process class.

A quick code-sample would be along these lines:

File.WriteAllText (
    @"C:\temp\myFile.txt", 
    "This is my letter header\nIt has a new-line in it")
Process.Start("notepad.exe", @"C:\temp\myFile.txt");

1. Use Process.Start with the property ShellExecute set to true;
2. Use the clipboard: http://www.dreamincode.net/forums/topic/40011-how-do-i-put-text-in-another-program/

Update

Process.Start returns a Process object which has a MainWindowHandle property. Use that handle when sending text instead of the FindWindow in the above mentioned link.

Update 2

Some code

Const WM_SETTEXT As Integer = &HC
<DllImport("user32.dll")> _
Private Shared Function SendMessage(hWnd As IntPtr, Msg As Integer, wParam As IntPtr, <MarshalAs(UnmanagedType.LPStr)> lParam As String) As IntPtr
End Function

Private Shared Sub Main()
    'ProcessStartInfo is used to instruct the Process class
    ' on how to start a new process. The UseShellExecute tells
    ' the process class that it (amongst other) should search for the application
    ' using the PATH environment variable.
    Dim pis As ProcessStartInfo = New ProcessStartInfo("notepad.exe")
    pis.UseShellExecute = True

    ' The process class is used to start the process
    ' it returns an object which can be used to control the started process
    Dim notepad As Process = Process.Start(pis)

    ' SendMessage is used to send the clipboard message to notepad's
    ' main window.
    Dim textToAdd As String = "Text to add"
    SendMessage(notepad.MainWindowHandle, WM_SETTEXT, IntPtr.Zero, textToAdd)
End Sub

The trick here is to make a text file, and pass it to Notepad as a command line argument, or, if Notepad is the default application for ".txt", you can shell straight to the filename.

Creating/editing textfile through VB.NET

Launch and watch a process from VB.NET 2010

You can use the arguments collection ProcessStartInfo to pass the filename if required.