GetWindowText() in Win32 C++ is not working

following code is not working .i am trying to get text from edit control but it does not work.m tired by trying all possible codes looking documentation on msdn etc...

case WM_COMMAND:
    switch(LOWORD(wParam)){
    case 1:
        ::MessageBox(hwnd,"button clicked","message",MB_OK);
        break;
    case 2: 
        TCHAR t[20]; // 
            GetWindowText(text_box,t,19);// this is not working????????????????
        ::MessageBox(hwnd,t,t,MB_OK);
        cout<<t;



        break;

for refrence below is the complete code :

#include <windows.h>
#include<iostream>
using namespace std;

const char g_szClassName[] = "myWindowClass";

// Step 4: the Window Procedure
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    HWND text_field, button , text_box;
    char text_saved[20];

    switch(msg)

    {   case WM_CREATE:
         text_field = CreateWindow("STATIC",
            "Hello World",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,20, 90,25,
            hwnd,
            NULL,NULL,NULL);
        button = CreateWindow("BUTTON",
            "push button",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,50, 100,20,
            hwnd,
            (HMENU)1,NULL,NULL  
            )  ;
        text_box = CreateWindow("EDIT",
            " ",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,80, 200,25,
            hwnd,
            NULL,NULL,NULL
            );
        CreateWindow("BUTTON",
            "Save",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,120, 100,20,
            hwnd,
            (HMENU)2,NULL,NULL  
            );





    break;
    case WM_COMMAND:
        switch(LOWORD(wParam)){
        case 1:
            ::MessageBox(hwnd,"button clicked","message",MB_OK);
            break;
        case 2: 
            TCHAR t[20];
                GetWindowText(text_box,t,19);
            ::MessageBox(hwnd,t,t,MB_OK);
            cout<<t;



            break;



    }
    break;

        case WM_CLOSE:
            DestroyWindow(hwnd);
        break;
        case WM_DESTROY:
            PostQuitMessage(0);
        break;
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

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

    //Step 1: Registering the Window Class
    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_WINDOW+1);
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = g_szClassName;
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

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

    // Step 2: Creating the Window
    hwnd = CreateWindowEx(
        WS_EX_CLIENTEDGE,
        g_szClassName,
        "The title of my window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 500,500,
        NULL, NULL, hInstance, NULL);

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

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

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