问一下为什么我的程序弹出的messageBox关不了,而且修改之后第二次编译的时候会不能写入，是进程没有关掉吗?

// graphics.cpp : 定义应用程序的入口点。

//



#include "framework.h"

#include "graphics.h"

#include <string.h>

#include <atltypes.h>

#include "uart.h"

#include "serialcom.h"



#define MAX_LOADSTRING 100



// 全局变量:

HINSTANCE hInst;								// 当前实例

WCHAR szTitle[MAX_LOADSTRING];                  // 标题栏文本

WCHAR szWindowClass[MAX_LOADSTRING];			// 主窗口类名	



// 此代码模块中包含的函数的前向声明:

BOOL                InitInstance(HINSTANCE, int);

LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);

BOOL CALLBACK DialogProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam);

INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);



int APIENTRY wWinMain(_In_ HINSTANCE hInstance,

                     _In_opt_ HINSTANCE hPrevInstance,

                     _In_ LPWSTR    lpCmdLine,

                     _In_ int       nCmdShow)

{

    UNREFERENCED_PARAMETER(hPrevInstance);

    UNREFERENCED_PARAMETER(lpCmdLine);



    // TODO: 在此处放置代码。

	

    // 初始化全局字符串

    LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);

	LoadStringW(hInstance, IDC_GRAPHICS, szWindowClass, MAX_LOADSTRING);



    // 执行应用程序初始化:

    if (!InitInstance (hInstance, nCmdShow))

    {

        return FALSE;

    }



    HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_GRAPHICS));



    MSG msg;



    // 主消息循环:

    while (GetMessage(&msg, NULL, 0, 0))

    {

        if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))

        {

            TranslateMessage(&msg);

            DispatchMessage(&msg);

        }

    }



    return (int) msg.wParam;

}



//

//   函数: InitInstance(HINSTANCE, int)

//

//   目标: 保存实例句柄并创建主窗口

//

//   注释:

//

//        在此函数中，我们在全局变量中保存实例句柄并

//        创建和显示主程序窗口。

//

BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)

{

   hInst = hInstance; // 将实例句柄存储在全局变量中

   /*主窗口*/

   HWND hWnd = CreateDialogW(hInst, MAKEINTRESOURCE(IDD_DIALOG_UART), NULL, About);

   if (!hWnd)

   {

      return FALSE;

   }



   ShowWindow(hWnd, nCmdShow);

   UpdateWindow(hWnd);



   return TRUE;

}





//文本框的处理程序。

BOOL CALLBACK DialogProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)

{

	switch (uMsg)

	{	

	case WM_COMMAND:

		MessageBox(hwndDlg, L"点击了文本框!\n", L"成功", MB_OK);

	}

	return (INT_PTR)FALSE;

}



// “关于”框的消息处理程序。

INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)

{

    UNREFERENCED_PARAMETER(lParam);

	static HWND hOpen;                   /*打开串口句柄*/

	static HWND hBaudRate;				 /*波特率句柄*/

	static HWND hGet;				     /*收数据框句柄*/

	static HWND hSend;				     /*发数据框句柄*/

	static HWND hDefCom;				 /*默认单选句柄*/

	static DWORD dwBaudrate = 1200;      /*波特率大小*/

	static int iPushtimes = 0;           /*波特率按钮按下次数*/

	static BOOL bOpenUart = FALSE;       /*是否打开了串口*/

	static uart myuart;                  /*串口对象*/

	TCHAR buffer[255];					/*UNICODE数据缓存*/

	char cBuffer[255];					/*ANSI*/

	DWORD baudrate;						/*波特率*/

    switch (message)

    {

    case WM_INITDIALOG:

		hOpen = GetDlgItem(hDlg, IDC_BUTTON_OPENCOMM);

		hBaudRate = GetDlgItem(hDlg, IDC_COMBO_BAUDRATE);

		hGet = GetDlgItem(hDlg, IDC_EDIT_RECEIVE);

		hSend = GetDlgItem(hDlg, IDC_EDIT_SEND);

		myuart.inithRec(hGet);

		SendMessage(hBaudRate, CB_ADDSTRING, 0, (LPARAM)_T("4800"));

		SendMessage(hBaudRate, CB_ADDSTRING, 0, (LPARAM)_T("9600"));

		SendMessage(hBaudRate, CB_ADDSTRING, 0, (LPARAM)_T("115200"));

		SendMessage(hBaudRate, CB_SETCURSEL, 0, 0);

        return (INT_PTR)TRUE;

    case WM_COMMAND:

		switch (LOWORD(wParam))

		{

		case IDC_BUTTON_OPENCOMM:

			SendMessage(hBaudRate, WM_GETTEXT, (WPARAM)20, (LPARAM)buffer);

			uart::TcharToChar(buffer, cBuffer);

			sscanf_s(cBuffer, "%d", &baudrate);

			if (!myuart.openCOM(baudrate))

			{

				MessageBox(hDlg, TEXT("打开串口失败!"), TEXT("错误"), MB_OK | MB_ICONERROR);

			}

		case IDC_COMBO_BAUDRATE:

			

			break;

		default:

			break;

		}

		break;

	case WM_DESTROY:

		PostQuitMessage(0);

		break;

	case WM_QUIT:

		EndDialog(hDlg, LOWORD(wParam));

		break;

    }

	return DefWindowProc(hDlg, message, wParam, lParam);

}