[C++/CLI]Send WM_GETTEXT Message from Managed

I've read interesting question from msdn forum.


He is going to Send WM_GETTEXT Message to other window's child control from CLI program.



I thought it'll very helpful for my study.
I use IneropServices namespace.
It's for call unmanaged function easily.

using namespace System;

using namespace System::Runtime::InteropServices;

using namespace System::Text;

[DllImport("User32.dll", EntryPoint = "FindWindow",CallingConvention = CallingConvention::Cdecl, CharSet = CharSet::Ansi)]

IntPtr FindWindow(
System::String^ lpClassName, System::String^
lpWindowName);

[DllImport("User32.dll", EntryPoint =
"FindWindowEx",CallingConvention = CallingConvention::Cdecl, CharSet =
CharSet::Ansi)]

IntPtr FindWindowEx( IntPtr parent, IntPtr childAfter,
System::String^ lpClassName, System::String^ lpWindowName);

[DllImport("user32.dll", EntryPoint =
"SendMessage", CallingConvention =
CallingConvention::Cdecl, CharSet = CharSet::Ansi)]

IntPtr SendMessage(IntPtr
hWnd, System::UInt32 Msg, IntPtr wParam,
IntPtr lParam);

After declaring unmanaged function explicitly, You can easily using unmanaged function with InteropServices.

Important thing is Be aware of managed and unmanaged type compatible.

IntPtr is for HWND( == void*) type.

Then I'm going to find window and send WM_GETTEXT message to it's child window.

const UInt32 WM_GETTEXT = 0x000D;

IntPtr wp, lp;

Char str[100] = {0,}; //buffer for child control's text

Int32 len =20;

//Find Window caption is "FindWindowTest"

IntPtr Parenthwnd = FindWindow(nullptr, "FindWindowTest");

//Then Find Parenthwnd window's child Edit control

IntPtr childWnd = FindWindowEx(Parenthwnd, (IntPtr)0, "Edit", nullptr);

//Then Send WM_GETTEXT Message

IntPtr r = SendMessage(childWnd, WM_GETTEXT,

safe_cast(len), safe_cast<IntPtr>(str));

Then I got a some text from Edit box.

But It's broken..

Because, C++/CLI using Unicode, but Edit box is not.

So I should convert it.

C++/CLI support various converting classes.

UTF32Encoding^ u32LE = gcnew UTF32Encoding(false, true,true );

String^ UnicodeStr = gcnew String(str);

array^myBytes = gcnew array(u32LE->GetByteCount( UnicodeStr ));

u32LE->GetBytes(UnicodeStr, 0, UnicodeStr->Length, myBytes,0 );

array^ newBytes = gcnew array(myBytes->Length);

//myBytes still has problem.

//after encoding UTF32, there are double null character.

//below code eliminate double null character.

int destIdx = 0;

for (int idx=0; idxLength-1; idx++)

{

if (idx+1 != myBytes->Length)

{

if(myBytes[idx] == 0 && myBytes[idx] == 0)

{

idx++;

}

else

{

newBytes[destIdx++] = myBytes[idx];

}

}

}

//newBytes is ASCII Code. Still can't get text

//It shoud be Decode.

array<Char>^ chars = gcnew array(100);

Decoder^ d = Encoding::ASCII->GetDecoder();

int charLen = d->GetChars(newBytes, 0, newBytes->Length, chars, 0);

String^ ConvertedStr = gcnew String(chars);

//Finally we got text, we can read