Win32 API VS C++;要字符串的文本框内容

我是Win32应用程序编程的新手。我已经编程了一个文本框，用户可以在其中输入文本。问题是，我不知道如何将框的输入转换为字符串，这是处理输入所必需的。出于测试目的，我试图通过输出文本框输出输入的文本，无论如何我都必须对其进行编程。

在谷歌上搜索，我发现GetWindowTextA(hInput, input, length);应该做到这一点。然而，我不确定如何使用这种方法将输入输入到变量中。

所以，我的问题是，如何将用户输入到文本框中的文本转换为字符串？

如果这真的很重要：我没有使用免费版本的Visual Studio，因为我可以通过我的大学免费访问Microsoft软件。目前我正在使用Visual Studio 2015终极预览版。为了提前回答这个问题，这不是我所在大学的家庭作业或其他工作，也不是工作或任何商业活动。我自学了C++，它已经成为我最喜欢的编程语言，我希望能够用它来编程图形界面

以下是Visual Studio的标准代码，经过了一些修改，最引人注目的是添加了两个文本框和一个按钮(目前没有任何作用，对这个问题也不重要)：

Includes、globals、forward声明

#include "stdafx.h"
#include "WilliTeX.h"
#include <iostream>;
using namespace std;
#define MAX_LOADSTRING 100
//custom defines
#define TEXT_INPUT_BOX 1
#define TEXT_OUTPUT_BOX 2
#define BUTTON 3
HWND hInput;
HWND hOutput;
HWND hButton;
int length;
LPSTR input;
// Global Variables:
HINSTANCE hInst;                                // current instance
TCHAR szTitle[MAX_LOADSTRING];                  // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING];            // the main window class name

// Forward declarations of functions included in this code module:
ATOM                MyRegisterClass(HINSTANCE hInstance);
BOOL                InitInstance(HINSTANCE, int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);

_tWinMain

int APIENTRY _tWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPTSTR    lpCmdLine,
_In_ int       nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
MSG msg;
HACCEL hAccelTable;
// Initialize global strings
LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
LoadString(hInstance, IDC_WILLITEX, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);
// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}
hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_WILLITEX));
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;
}

MyRegisterClass

//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style          = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc    = WndProc;
wcex.cbClsExtra     = 0;
wcex.cbWndExtra     = 0;
wcex.hInstance      = hInstance;
wcex.hIcon          = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_WILLITEX));
wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName   = MAKEINTRESOURCE(IDC_WILLITEX);
wcex.lpszClassName  = szWindowClass;
wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassEx(&wcex);
}

代码的其余部分

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
HWND hWnd;
hInst = hInstance; // Store instance handle in our global variable
hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
return TRUE;
}
//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE:  Processes messages for the main window.
//
//  WM_COMMAND  - process the application menu
//  WM_PAINT    - Paint the main window
//  WM_DESTROY  - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
switch (message)
{
case WM_CREATE:
{
//This is the input box, where the user enters the text
hInput = CreateWindowExA(WS_EX_CLIENTEDGE,
"EDIT",
"",
WS_CHILD | WS_VISIBLE | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL,
50, //moving left/right the box
10, //moving up/down the box
1300, //length
350, //height
hWnd,
(HMENU)TEXT_INPUT_BOX,
GetModuleHandle(NULL),
NULL);
//This is the output text box, that will display the convertion
hInput = CreateWindowExA(WS_EX_CLIENTEDGE,
"Edit", 
"test",
WS_CHILD | WS_VISIBLE | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL,
50, //moving left/right the box
200, //moving up/down the box
1300, //length
450, //height
hWnd, 
(HMENU)TEXT_INPUT_BOX,
GetModuleHandle(NULL),
NULL);
hButton = CreateWindowExA(NULL,
"BUTTON",
"OK",
WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,
3, //moving left/right
10, //moving up/down
48, //length
50, //height
hWnd,
(HMENU) BUTTON,
GetModuleHandle(NULL),
NULL);
break;
}
case WM_COMMAND:
wmId    = LOWORD(wParam);
wmEvent = HIWORD(wParam);
switch (LOWORD(wParam)) {
//refreshing the output box whenever the user is giving an input
case TEXT_INPUT_BOX:
{
length = GetWindowTextLengthA(hInput);
GetWindowTextA(hInput, input, length);
hInput = CreateWindowExA(WS_EX_CLIENTEDGE,
"Edit",
input,
WS_CHILD | WS_VISIBLE | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL,
50, //moving left/right the box
200, //moving up/down the box
1300, //length
450, //height
hWnd,
(HMENU)TEXT_INPUT_BOX,
GetModuleHandle(NULL),
NULL);
break;
}
case BUTTON:
{
break;
}
}
// Parse the menu selections:
switch (wmId)
{
case IDM_ABOUT:
DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
break;
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code here...
EndPaint(hWnd, &ps);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
UNREFERENCED_PARAMETER(lParam);
switch (message)
{
case WM_INITDIALOG:
return (INT_PTR)TRUE;
case WM_COMMAND:
if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
{
EndDialog(hDlg, LOWORD(wParam));
return (INT_PTR)TRUE;
}
break;
}
return (INT_PTR)FALSE;
}

附言：我知道使用命名空间std；这是一种糟糕的编码实践，但对于这个学习程序，我真的不在乎。