GetWindowText() retrieving nothing from my edit control

#include <windows.h>
#include <stdio.h>

#pragma comment (lib, "comctl32.lib")
#pragma comment(linker,"\"/manifestdependency:type='win32' \
name='Microsoft.Windows.Common-Controls' version='6.0.0.0' \
processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK printout(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
HWND mainwindow;
HWND editbox;
HWND sendbutton;
HWND printbox;
HFONT hFont = (HFONT)GetStockObject(DEFAULT_GUI_FONT);

#define PO_ADDTEXT (WM_USER + 1)

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wc;
	WNDCLASSEX print;
    MSG Msg;

    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.style         = 0;
    wc.lpfnWndProc   = WndProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInstance;
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH) COLOR_BACKGROUND + 1;
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = "clientstuffs";
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&wc))
    {
        MessageBox(NULL, "Window Registration Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    print.cbSize        = sizeof(WNDCLASSEX);
    print.style         = 0;
    print.lpfnWndProc   = printout;
    print.cbClsExtra    = 0;
    print.cbWndExtra    = 0;
    print.hInstance     = hInstance;
    print.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    print.hCursor       = LoadCursor(NULL, IDC_ARROW);
    print.hbrBackground = (HBRUSH) CreateSolidBrush(RGB(255,255,255));
    print.lpszMenuName  = NULL;
    print.lpszClassName = "printbox";
    print.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

	if(!RegisterClassEx(&print))
    {
        MessageBox(NULL, "Window Registration Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    mainwindow = CreateWindowEx(
        WS_EX_CLIENTEDGE,
        "clientstuffs",
        "The title of my window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 600, 500,
        NULL, NULL, hInstance, NULL);

	editbox = CreateWindowEx(0, "EDIT", "",
                      WS_VISIBLE | WS_CHILD | WS_BORDER | ES_LEFT,
                      40, 410, 420, 30,
                      mainwindow,
                      (HMENU)5, hInstance, NULL);
	SendMessage(editbox, WM_SETFONT, (WPARAM)hFont, MAKELPARAM(TRUE, 0));

	
	printbox = CreateWindowEx(0, "printbox", "",
					   WS_VISIBLE | WS_CHILD | WS_BORDER | WS_VSCROLL,
					   40, 40, 420, 360,
					   mainwindow,
					   NULL, hInstance, NULL);

	sendbutton = CreateWindowEx( 0, "BUTTON", "Send",
					WS_VISIBLE | WS_CHILD | BS_CENTER | BS_VCENTER,
					470, 410, 70, 30,
					mainwindow,
					(HMENU)5, hInstance, NULL);
	SendMessage(sendbutton, WM_SETFONT, (WPARAM)hFont, MAKELPARAM(TRUE, 0));

    if(mainwindow == NULL)
    {
        MessageBox(NULL, "Window Creation Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(mainwindow, nCmdShow);
    UpdateWindow(mainwindow);

    // Step 3: The Message Loop
    while(GetMessage(&Msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	static LPTSTR textmessage = "";
	static char buffer[256];

    switch(msg)
    {
        case WM_CLOSE:
            DestroyWindow(hwnd);
        break;
        case WM_DESTROY:
            PostQuitMessage(0);
        break;

		case WM_KEYDOWN:
			{
				switch (wParam)
				{
					case VK_RETURN:
					{	
						SendMessage(sendbutton, BM_CLICK, 0, 0);
					}
				}
				break;
			}

		case WM_COMMAND:
			{
				switch(HIWORD(wParam))
				{
					case BN_CLICKED:
					{
						SendMessage(editbox, WM_GETTEXT, (WPARAM) 256, (LPARAM) textmessage);
						//GetWindowText(editbox, textmessage, 256);
						sprintf(buffer,"number of chacacters copied : %i", strlen(textmessage));
						MessageBox(hwnd, buffer, "yerp", MB_OK);
						SetWindowText(editbox, "");
						SendMessage(printbox, PO_ADDTEXT, (WPARAM) textmessage , 0);
					}
				}
				break;
			}
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

LRESULT CALLBACK printout(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	HDC hdc;
	static PAINTSTRUCT paint;
	static RECT textbox = {20, 20, 373, 200};
	static RECT clientrect;
	static char prompt[50000] = "this is a testing string filled with a bunch of insignifigant words where i fill the string to make it as large as possible so that it makes testing the string in multiple lines possible";
	static char linebreak[3] = "\n\n";
	switch(msg)
	{
		case WM_CLOSE:
		{
                        DestroyWindow(hwnd);
			break;
		}
                case WM_DESTROY:
		{
			PostQuitMessage(0);
			break;
		}
		case WM_PAINT:
		{
			hdc = BeginPaint(hwnd, &paint);

				SelectObject(hdc, hFont);
				DrawText(hdc, prompt, strlen(prompt), &textbox, DT_CALCRECT | DT_WORDBREAK);
				DrawText(hdc, prompt, strlen(prompt), &textbox, DT_WORDBREAK);

			EndPaint(hwnd, &paint);
			break;
		}
		case PO_ADDTEXT:
		{
			strcat(prompt, linebreak);
			strcat(prompt, (char*) wParam);
			GetClientRect(printbox, &clientrect);
			InvalidateRect(printbox, &clientrect, true);
			break;
		}
		default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}