.NET Windows Form 改變窗體類名（Class Name）有多難？

　　研究WinForm的東西，是我的一個個人興趣和愛好，以前做的項目，多與WinForm相關，然而這幾年，項目都與WinForm沒什么關系了，都轉為ASP.NET MVC與WPF了。關於今天討論的這個問題，以前也曾深入研究過，只是最近有朋友問到這個問題，就再挖挖這個墳（坑）。

一、類名是啥？

 　　打開神器SPY++，VS2013 在【工具】菜單里：　　

　　VS2013之前的VS版本，在【開始菜單】里：

　　打開SPY++，點擊標注的按鈕，

　　在打開的窗口上，把雷達按鈕拖到你想查看的窗口，就可以看到它的類名了，下面就是QQ的類名：

　　再看看.NET WinForm的窗體類名：

　　一大串啊，有沒有，我不想這樣，我想要一個有個性的、簡單的類名，咋辦？

二、 不是有個CreateParams屬性嗎？

　　作為一個有多年WinForm開發經驗的程序猿，這有啥難的，WinForm的控件不是都有個CreateParams屬性嗎？里面可以不是就可以設置窗口類名嗎？看看：

　　真的有，這不就簡單了嘛，動手，於是有下面代碼：　　

    public partial class FormMain : Form
    {
        public FormMain()
        {
            InitializeComponent();
        }

        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams createParams = base.CreateParams;
                createParams.ClassName = "Starts2000.Window"; //這就是我想要的窗體類名。
                return createParams;
            }
        }
    }

　　編譯，運行，結果卻是這樣的：　　

 

　　泥煤啊，這是什么啊，翻~牆，一通谷歌，原來類名使用前都需要注冊啊，難道微軟只注冊了自己的類名，我個性化的他就不幫我注冊，那我就自己注冊吧，坑爹的微軟啊。

三、注冊一個窗口類名吧

　　注冊窗口類名需要用到Windows API函數了，用C#進行P/Invoke？太麻煩了，做了這么多年的WinForm開發，我可是練了《葵花寶典（C++/CLI）》的，只是因為沒自宮，所以沒大成，不過，簡單用用還是可以的。

　　創建一個C++空項目，設置項目屬性-配置屬性-常規，如下圖：　　

　　於是有了下面的代碼：

　　1. FormEx.h

#pragma once
#include <Windows.h>
#include <vcclr.h>

#define CUSTOM_CLASS_NAME  L"Starts2000.Window"

namespace Starts2000
{
	namespace WindowsClassName
	{
		namespace Core
		{
			using namespace System;
			using namespace System::Windows::Forms;
			using namespace System::Runtime::InteropServices;

			private delegate LRESULT WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

			public ref class FormEx :
				public Form
			{
			public:
				static FormEx();
				FormEx();
			private:
				static LRESULT WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
				static void ProcessExit(Object^ sender, EventArgs^ e);
			};
		}
	}
}

　　2. FormEx.cpp　　

#include "FormEx.h"

namespace Starts2000
{
	namespace WindowsClassName
	{
		namespace Core
		{
			static FormEx::FormEx()
			{
				WNDCLASSEX wc;
				Starts2000::WindowsClassName::Core::WndProc ^windowProc =
					gcnew Starts2000::WindowsClassName::Core::WndProc(FormEx::WndProc);
				pin_ptr<Starts2000::WindowsClassName::Core::WndProc^> pWindowProc = &windowProc;

				ZeroMemory(&wc, sizeof(WNDCLASSEX));
				wc.cbSize = sizeof(WNDCLASSEX);
				wc.style = CS_DBLCLKS;
				wc.lpfnWndProc = reinterpret_cast<WNDPROC>(Marshal::GetFunctionPointerForDelegate(windowProc).ToPointer());
				wc.hInstance = GetModuleHandle(NULL);
				wc.hCursor = LoadCursor(NULL, IDC_ARROW);
				wc.hbrBackground = (HBRUSH)COLOR_WINDOW; //(HBRUSH)GetStockObject(HOLLOW_BRUSH);
				wc.lpszClassName = CUSTOM_CLASS_NAME;

				ATOM classAtom = RegisterClassEx(&wc);
				DWORD lastError = GetLastError();
				if (classAtom == 0 && lastError != ERROR_CLASS_ALREADY_EXISTS)
				{
					throw gcnew ApplicationException("Register window class failed!");
				}

				System::AppDomain::CurrentDomain->ProcessExit += gcnew System::EventHandler(FormEx::ProcessExit);
			}

			FormEx::FormEx() : Form()
			{
			}

			LRESULT FormEx::WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
			{
				System::Windows::Forms::Message message = System::Windows::Forms::Message::Create((IntPtr)hWnd,
					(int)msg, (IntPtr)((void*)wParam), (IntPtr)((void*)lParam));
				System::Diagnostics::Debug::WriteLine(message.ToString());
				return DefWindowProc(hWnd, msg, wParam, lParam);
			}

			void FormEx::ProcessExit(Object^ sender, EventArgs^ e)
			{
				UnregisterClass(CUSTOM_CLASS_NAME, GetModuleHandle(NULL));
			}
		}
	}
}

　　3. 創建一個C# WinForm項目，引用上面創建的C++/CLI項目生成的DLL，代碼跟最開始的區別不大。　　

    public partial class FormMain : /*Form*/ FormEx
    {
        public FormMain()
        {
            InitializeComponent();
        }

        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams createParams = base.CreateParams;
                createParams.ClassName = "Starts2000.Window"; //這就是我想要的窗體類名。
                return createParams;
            }
        }
    }

　　編譯，運行，結果卻仍然是這樣的：　　

　　泥煤啊，微軟到底干了什么，我只是想搞點小玩意，滿足下我的虛榮心，你竟然……，心中千萬頭“羊駝”奔騰而過。

　　沒辦法了，微軟不都開源了嗎，也不需要反編譯了，直接下源代碼看吧。

四、也不反編譯了，直接找源代碼看吧

　　在微軟的網站（http://referencesource.microsoft.com/）Down下代碼，從Form→ContainerControl→ScrollableControl→Control，在Control里找到NativeWindow，再在NativeWindow里面找到了WindowClass，在WindowClass里找到了坑爹的RegisterClass方法，恍然大悟了，有沒有，具體看代碼，我加了注釋。　　

private void RegisterClass() {
    NativeMethods.WNDCLASS_D wndclass = new NativeMethods.WNDCLASS_D();

    if (userDefWindowProc == IntPtr.Zero) {
        string defproc = (Marshal.SystemDefaultCharSize == 1 ? "DefWindowProcA" : "DefWindowProcW");

        userDefWindowProc = UnsafeNativeMethods.GetProcAddress(new HandleRef(null, UnsafeNativeMethods.GetModuleHandle("user32.dll")), defproc);
        if (userDefWindowProc == IntPtr.Zero) {
            throw new Win32Exception();
        }
    }

    string localClassName = className;

    if (localClassName == null) {  //看看是否自定義了classnName，就是我們在 CreateParams ClassName設置的值。

        // If we don't use a hollow brush here, Windows will "pre paint" us with COLOR_WINDOW which
        // creates a little bit if flicker.  This happens even though we are overriding wm_erasebackgnd.
        // Make this hollow to avoid all flicker.
        //
        wndclass.hbrBackground = UnsafeNativeMethods.GetStockObject(NativeMethods.HOLLOW_BRUSH); //(IntPtr)(NativeMethods.COLOR_WINDOW + 1);
        wndclass.style = classStyle;

        defWindowProc = userDefWindowProc;
        localClassName = "Window." + Convert.ToString(classStyle, 16);
        hashCode = 0;
    }
    else {   //坑爹的就在這里了
        NativeMethods.WNDCLASS_I wcls = new NativeMethods.WNDCLASS_I();
        /*注意下面這句代碼，特別注意 NativeMethods.NullHandleRef，MSDN說明：
            * BOOL WINAPI GetClassInfo(
            *    _In_opt_ HINSTANCE  hInstance,
            *    _In_     LPCTSTR    lpClassName,
            *    _Out_    LPWNDCLASS lpWndClass
            *  );
            * hInstance [in, optional]
            *  Type: HINSTANCE
            *  A handle to the instance of the application that created the class. 
            * To retrieve information about classes defined by the system (such as buttons or list boxes),
            * set this parameter to NULL.
            * 就是說，GetClassInfo 的第一個參數為 NULL(NativeMethods.NullHandleRef)的時候，只有系統注冊的 ClassName
            * 才會返回 True，所以當我們設置了CreateParams ClassName的值后，只要設置的不是系統注冊的 ClassName，都會
            * 拋出后面的 Win32Exception 異常，泥煤啊。
        */
        bool ok = UnsafeNativeMethods.GetClassInfo(NativeMethods.NullHandleRef, className, wcls);
        int error = Marshal.GetLastWin32Error();
        if (!ok) {
            throw new Win32Exception(error, SR.GetString(SR.InvalidWndClsName));
        }
        wndclass.style = wcls.style;
        wndclass.cbClsExtra = wcls.cbClsExtra;
        wndclass.cbWndExtra = wcls.cbWndExtra;
        wndclass.hIcon = wcls.hIcon;
        wndclass.hCursor = wcls.hCursor;
        wndclass.hbrBackground = wcls.hbrBackground;
        wndclass.lpszMenuName = Marshal.PtrToStringAuto(wcls.lpszMenuName);
        localClassName = className;
        defWindowProc = wcls.lpfnWndProc;
        hashCode = className.GetHashCode();
    }

    // Our static data is different for different app domains, so we include the app domain in with
    // our window class name.  This way our static table always matches what Win32 thinks.
    // 
    windowClassName = GetFullClassName(localClassName);
    windowProc = new NativeMethods.WndProc(this.Callback);
    wndclass.lpfnWndProc = windowProc;
    wndclass.hInstance = UnsafeNativeMethods.GetModuleHandle(null);
    wndclass.lpszClassName = windowClassName;

    short atom = UnsafeNativeMethods.RegisterClass(wndclass);
    if (atom == 0) {

        int err = Marshal.GetLastWin32Error();
        if (err == NativeMethods.ERROR_CLASS_ALREADY_EXISTS) {
            // Check to see if the window class window
            // proc points to DefWndProc.  If it does, then
            // this is a class from a rudely-terminated app domain
            // and we can safely reuse it.  If not, we've got
            // to throw.
            NativeMethods.WNDCLASS_I wcls = new NativeMethods.WNDCLASS_I();
            bool ok = UnsafeNativeMethods.GetClassInfo(new HandleRef(null, UnsafeNativeMethods.GetModuleHandle(null)), windowClassName, wcls);
            if (ok && wcls.lpfnWndProc == NativeWindow.UserDefindowProc) {

                // We can just reuse this class because we have marked it
                // as being a nop in another domain.  All we need to do is call SetClassLong.
                // Only one problem:  SetClassLong takes an HWND, which we don't have.  That leaves
                // us with some tricky business. First, try this the easy way and see
                // if we can simply unregister and re-register the class.  This might
                // work because the other domain shutdown would have posted WM_CLOSE to all
                // the windows of the class.
                if (UnsafeNativeMethods.UnregisterClass(windowClassName, new HandleRef(null, UnsafeNativeMethods.GetModuleHandle(null)))) {
                    atom = UnsafeNativeMethods.RegisterClass(wndclass);
                    // If this fails, we will always raise the first err above.  No sense exposing our twiddling.
                }
                else {
                    // This is a little harder.  We cannot reuse the class because it is
                    // already in use.  We must create a new class.  We bump our domain qualifier
                    // here to account for this, so we only do this expensive search once for the
                    // domain.  
                    do {
                        domainQualifier++;
                        windowClassName = GetFullClassName(localClassName);
                        wndclass.lpszClassName = windowClassName;
                        atom = UnsafeNativeMethods.RegisterClass(wndclass);
                    } while (atom == 0 && Marshal.GetLastWin32Error() == NativeMethods.ERROR_CLASS_ALREADY_EXISTS);
                }
            }
        }

        if (atom == 0) {
            windowProc = null;
            throw new Win32Exception(err);
        }
    }
    registered = true;
}

五、嚇尿了！自己動手，豐衣足食

　　看到微軟的源碼后，只能表示尿了，不可能繼承Form實現自定義類名了，那么就自己動手，豐衣足食吧，還記得上面的C++/CLI代碼吧，簡單的加一些內容，就可以實現我們自定義窗口類名的願望了，代碼如下：　　

　　1. CustomForm.h　　

#pragma once

#include <Windows.h>
#include <vcclr.h>

#define CUSTOM_CLASS_NAME  L"Starts2000.Window"

namespace Starts2000
{
	namespace WindowsClassName
	{
		namespace Core
		{
			using namespace System;
			using namespace System::Windows::Forms;
			using namespace System::Runtime::InteropServices;

			private delegate LRESULT WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

			public ref class CustomForm
			{
			public:
				static CustomForm();
				CustomForm();
				CustomForm(String ^caption);
				~CustomForm();
				void Create();
				void Show();
			private:
				String ^_caption;
				HWND _hWnd;
				static GCHandle _windowProcHandle;
				static LRESULT WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
				static void ProcessExit(Object^ sender, EventArgs^ e);
			};
		}
	}
}

　　2. CustomForm.cpp

#include "CustomForm.h"

namespace Starts2000
{
	namespace WindowsClassName
	{
		namespace Core
		{
			static CustomForm::CustomForm()
			{
				WNDCLASSEX wc;
				Starts2000::WindowsClassName::Core::WndProc ^windowProc =
					gcnew Starts2000::WindowsClassName::Core::WndProc(CustomForm::WndProc);
				_windowProcHandle = GCHandle::Alloc(windowProc);

				ZeroMemory(&wc, sizeof(WNDCLASSEX));
				wc.cbSize = sizeof(WNDCLASSEX);
				wc.style = CS_DBLCLKS;
				wc.lpfnWndProc = reinterpret_cast<WNDPROC>(Marshal::GetFunctionPointerForDelegate(windowProc).ToPointer());
				wc.hInstance = GetModuleHandle(NULL);
				wc.hCursor = LoadCursor(NULL, IDC_ARROW);
				wc.hbrBackground = (HBRUSH)COLOR_WINDOW; //(HBRUSH)GetStockObject(HOLLOW_BRUSH);
				wc.lpszClassName = CUSTOM_CLASS_NAME;

				ATOM classAtom = RegisterClassEx(&wc);
				DWORD lastError = GetLastError();
				if (classAtom == 0 && lastError != ERROR_CLASS_ALREADY_EXISTS)
				{
					throw gcnew ApplicationException("Register window class failed!");
				}

				System::AppDomain::CurrentDomain->ProcessExit += gcnew System::EventHandler(CustomForm::ProcessExit);
			}

			CustomForm::CustomForm() : _caption("Starts2000 Custom ClassName Window")
			{
			}

			CustomForm::CustomForm(String ^caption) : _caption(caption)
			{
			}

			CustomForm::~CustomForm()
			{
				if (_hWnd)
				{
					DestroyWindow(_hWnd);
				}
			}

			void CustomForm::Create()
			{
				DWORD styleEx = 0x00050100;
				DWORD style = 0x17cf0000;

				pin_ptr<const wchar_t> caption = PtrToStringChars(_caption);

				_hWnd = CreateWindowEx(styleEx, CUSTOM_CLASS_NAME, caption, style,
					CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
					NULL, NULL, GetModuleHandle(NULL), NULL);
				if (_hWnd == NULL)
				{
					throw gcnew ApplicationException("Create window failed! Error code:" + GetLastError());
				}
			}

			void CustomForm::Show()
			{
				if (_hWnd)
				{
					ShowWindow(_hWnd, SW_NORMAL);
				}
			}

			LRESULT CustomForm::WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
			{
				System::Windows::Forms::Message message = System::Windows::Forms::Message::Create((IntPtr)hWnd,
					(int)msg, (IntPtr)((void*)wParam), (IntPtr)((void*)lParam));
				System::Diagnostics::Debug::WriteLine(message.ToString());
				
				if (msg == WM_DESTROY)
				{
					PostQuitMessage(0);
					return 0;
				}

				return DefWindowProc(hWnd, msg, wParam, lParam);
			}

			void CustomForm::ProcessExit(Object^ sender, EventArgs^ e)
			{
				UnregisterClass(CUSTOM_CLASS_NAME, GetModuleHandle(NULL));
				if (CustomForm::_windowProcHandle.IsAllocated)
				{
					CustomForm::_windowProcHandle.Free();
				}
			}
		}
	}
}

　　最后仍然用我們熟悉的C#來調用：

using System;
using System.Windows.Forms;
using Starts2000.WindowsClassName.Core;

namespace Starts2000.WindowClassName.Demo
{
    static class Program
    {
        /// <summary>
        /// 應用程序的主入口點。
        /// </summary>
        [STAThread]
        static void Main()
        {
            //Application.EnableVisualStyles();
            //Application.SetCompatibleTextRenderingDefault(false);
            //Application.Run(new FormMain());

            CustomForm form = new CustomForm();
            form.Create();
            form.Show();
            Application.Run();
        }
    }
}

　　編譯，運行，拿出神器SPY++看一看：

　　目標終於達成。

　　最后，所有代碼的下載（項目使用的是VS2013編譯、調試，不保證其他版本VS能正常編譯）：猛擊我。