How to Send Text to Notepad in C#/Win32

How to send text to Notepad in C#/Win32?

    [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
    public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
    [DllImport("User32.dll")]
    public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);
    private void button1_Click(object sender, EventArgs e)
    {
        Process [] notepads=Process.GetProcessesByName("notepad");
        if(notepads.Length==0)return;            
        if (notepads[0] != null)
        {
            IntPtr child= FindWindowEx(notepads[0].MainWindowHandle, new IntPtr(0), "Edit", null);
            SendMessage(child, 0x000C, 0, textBox1.Text);
        }
    }

WM_SETTEXT=0x000c

Write text to notepad with C#/Win32

Send EM_SETSEL to put the caret to the end of the edit window. Then send EM_REPLACESEL to append text.

This is much better than reading the entire contents, appending your addition and then setting the entire contents if the edit control contains a large amount of text.

These methods can cross 32/64 bit process boundaries without difficulty.

SendMessage to Notepad++ in C#

You are running into a string encoding issue. Strings in .NET are UTF-16 little-endian strings. The string "Send" in UTF-16 is actually the bytes S{0}e{0}n{0}d{0}{0}{0}. Your declaration of SendMessage is using the ANSI string method. There are a number of ways to solve this. Here's one: Explicitly use the UTF-16 form by changing SendMessage to SendMessageW.

[DllImport("User32.dll")]
public static extern int SendMessageW(IntPtr hWnd, int uMsg, int wParam, string lParam);

c# i'm unable to get SendMessage to send a message to a notepad window

Much credit to Remy. After some troubleshooting I ended up finding the code worked so it's a mystery why I was finding it didn't.

A good troubleshooting step is to try moving the window around with nircmd, so you know you have the handle.

To get the handle of the window, you can use nirsoft winlister, or winspector

You can use nircmd commands like nircmd win close handle 0x00230632 change that 0x00230632 to whatever you find the handle to be. Or better don't close it(otherwise you'll have to reopen it and the new window will have a new handle), so a command like nircmd win move handle 0x00B917AE 80 10 100 100 So you know the handle is right, regardless of any issue with the code.

Winspector also shows the child of the notepad window

Going back to the C# code, you can

skip the child and try writing into the parent, it should write into the title of the window

Try using SendMessage to specify a window directly. You write the handle in decimal rather than hex. e.g. if the handle is 3479948 then

e.g. SendMessage(new IntPtr(3479948), WM_SETTEXT, IntPtr.Zero, "abcdee");

You can also check that notepads[0].MainWindowHandle is picking up the correct value.. the handle shown in winspector.

You can look at the IntPtr child = FindWindowEx(...) line, make sure the 'child' is picking up the child handle.

You can try writing to that one directly with SendMessage. e.g. SendMessage(new IntPtr(1234567), WM_SETTEXT, IntPtr.Zero, "abcdee"); // (if winspector shows the child window to be that handle).

How to write and send text to mIRC in C#/Win32?

This code works for me (mirc 6.31):

IntPtr mainHandle = FindWindow("mIRC", null);
IntPtr serverHandle = FindWindowEx(mainHandle, new IntPtr(0), "MDIClient", null);  
IntPtr chanHandle = FindWindowEx(serverHandle, new IntPtr(0), "mIRC_Channel", null);  
IntPtr editHandle = FindWindowEx(chanHandle, new IntPtr(0), "richEdit20A", null);
SendMessage(editHandle, 0x000C, 0, "Hello World");

Notice the changed window class (richedit20A instead of edit). Just found the correct class by using Spy++.

As for the window handles, one possibility is to use the EnumWindows or EnumChildWindows API.

Send Message in C#

You don't need to send messages.

Add an event to the one form and an event handler to the other. Then you can use a third project which references the other two to attach the event handler to the event. The two DLLs don't need to reference each other for this to work.

SetText of textbox in external app. Win32 API

The following is what I've used successfully for that purpose w/ my GetLastError error checking removed/disabled:

[DllImport("user32.dll", SetLastError = false)]
public static extern IntPtr GetDlgItem(IntPtr hDlg, int nIDDlgItem);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)]
public static extern IntPtr SendMessage(HandleRef hWnd, uint Msg, IntPtr wParam, string lParam);
public const uint WM_SETTEXT = 0x000C;

private void InteropSetText(IntPtr iptrHWndDialog, int iControlID, string strTextToSet)
{
    IntPtr iptrHWndControl = GetDlgItem(iptrHWndDialog, iControlID);
    HandleRef hrefHWndTarget = new HandleRef(null, iptrHWndControl);
    SendMessage(hrefHWndTarget, WM_SETTEXT, IntPtr.Zero, strTextToSet);
}

I've tested this code and it works, so if it fails for you, you need to be sure that you are using the right window handle (the handle of the Dialog box itself) and the right control ID. Also try something simple like editing the Find dialog in Notepad.

I can't comment yet in the post regarding using (char *) but it's not necessary. See the second C# overload in p/Invoke SendMessage. You can pass String or StringBuilder directly into SendMessage.

I additionally note that you say that your control ID is 114. Are you certain WinSpector gave you that value in base 10? Because you are feeding it to GetDlgItem as a base 10 number. I use Spy++ for this and it returns control IDs in base 16. In that case you would use:

IntPtr boxHwnd = GetDlgItem(hWnd, 0x0114);

open new notepad.exe and write content to it

try this one source

 [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
        public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
        [DllImport("User32.dll")]
        public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);
        private void button1_Click(object sender, EventArgs e)
        {
            Process [] notepads=Process.GetProcessesByName("notepad");
            if(notepads.Length==0)return;            
            if (notepads[0] != null)
            {
                IntPtr child= FindWindowEx(notepads[0].MainWindowHandle, new IntPtr(0), "Edit", null);
                SendMessage(child, 0x000C, 0, textBox1.Text);
            }
        }

winapi - a standard way to retrieve text from running text editor

In general no there is no standard message for this.

But Windows' Notepad has an "Edit" child which responds to WM_GETTEXT and WM_GETTEXTLENGTH - messages normally used to retrieve text from input controls.

Here's a PoC demonstrating the idea:

#include <iostream>
#include <vector>
#include <string.h>
#include <Windows.h>

BOOL CALLBACK enumProc(HWND hwnd, LPARAM) {
    std::vector<char> buf(100);
    GetClassNameA(hwnd, buf.data(), 100);
    if (strcmp(buf.data(), "Notepad")) return TRUE;
    hwnd = FindWindowEx(hwnd, NULL, "Edit", NULL);
    if (!hwnd) return TRUE;
    int textLength = SendMessageA(hwnd, WM_GETTEXTLENGTH, 0, 0) + 1;
    if (textLength <= 0) return TRUE;
    buf.resize(textLength);
    SendMessage(hwnd, WM_GETTEXT, textLength, (LPARAM)buf.data());
    std::cout << buf.data() << "\n";
    return TRUE;
}

int main() {
    EnumWindows(&enumProc, 0);
}

Works on Windows 10:

Using WM_SETTEXT to set Notepad text is not affecting Text_Changed event in the Notepad instance

The edit control keeps the properties text and modified as distinct entities, allowing applications to build their own modification management around them. Sending a WM_SETTEXT message does not automatically set the modified flag. To set this flag you have to explicitly send an EM_SETMODIFY message to the edit control.

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