.Net WInform开发笔记(三)谈谈自制控件(自定义控件)_c#

末日这天写篇博客吧，既然没来，那就纪念一下。

这次谈谈自制控件，也就是自定义控件，先上图，再说

1.扩展openfiledialog，在openfiledialog中添加各种文件（.txt,.jpg,.excel等等）的预览功能

2.重写listbox，增加折叠、鼠标背影、分类等功能

-----------------------------分割线--------------------------------------------------------------
一、扩展openfiledialog

许多软件的打开对话框都有预览功能，最常见的就是图片预览，用鼠标选择一个图片文件后，右侧或者下侧就会有该图片的缩略图（photoshop中属于后者）。在winform编程中，有专门的打开文件对话框的类openfiledialog，但是他不提供文件预览功能，封装得实在太好。看看它公开那些接口

提到扩展，很多人可能想到继承它就可以扩展它，可惜openfiledialog声明为sealed，不允许从他继承。稍微底层一点的，想到可以通过win32 api来修改它的显示方式，只可惜，如你所见，它根本没提供handle属性，更别说handlecreated、handledestroyed等事件了。那么怎么样子搞呢？其实答案还是通过win32 api，只是我们取得它的句柄的方式要复杂一点而且调用api的时机隐晦了一点。

提示：

1.win32 api操作窗体需要知道窗体的句柄；

2.不熟悉win32编程的同学可以先上网查查资料，特别是不知道setparent、setwindowpos等api是干嘛的，我觉得以下的看不懂。

为什么说取得它的句柄复杂了一点？难道不是用“findwindow”、“findwindowex”、“ enumchildwindows”等获取openfiledialog的句柄，再用“setparent”、“setwindowpos”等api将.net控件（本例中是datagridview控件，当然可以使其他任何一种）添加到openfiledialog中去？没错，以上列举出来的api都是基本要用到的，“只是用在什么地方、什么时候用”是个比较麻烦的问题，原因如下：

1）我们知道openfiledialog显示的是模式对话框，也就是说，一旦它showdialog（），它以下的代码是不会再执行的，具体原因是什么（我以后的博客会专门讲为什么），你现在可以理解为openfiledialog()方法会阻塞调用线程，既然阻塞了调用线程，那么我们再无法控制程序了（直到它返回），根本谈不上再调用api获取openfiledialog的句柄然后去操作它。如果有人会说，“我可以另开辟线程去取openfiledialog得句柄再操作它”，恩，我不否定这个方法，只是我想说，如果你真的按照这个方法去试，那么肯定会陷入泥潭。因为你不仅要取它的句柄，你还要监视openfiledialog的一举一动，移动、缩放、用户鼠标点击选择文件、更改目录等，然后再操作.net控件（本例中是datagridview控件，下同），让.net控件去适应openfiledialog的大小等等，你会发现你忙死了，甚至有的你根本监视不了，比如用户点击选择文件、更改目录。

2）就算我们能够在openfiledialog显示之后，取得它的句柄，那么什么时候再调用其他api呢？比如什么时候调用setwindowpos，让.net控件适应openfiledialog的大小变化？什么时候知道用户选择文件发生了变化？

所以，api方法什么时候用？用在什么地方？就是接下来要讨论的东西。

我不知道各位在使用各种框架的时候，对“框架”的理解到什么程度，我觉得可以总结成一句话“跟个2b似地注册一些事件，然后苦逼地去写好每一个回调方法，我们却不知道为啥要这样写”，不是么？既然这样，那么我们的api方法只要写在了正确的回调方法中，我们就能到达想要的目的了。考虑几个问题：

1）openfiledialog显示，我们向其中添加.net控件。我们什么时候知道它显示？

2）openfiledialog大小发生变化时，我们要更新.net控件以适应新的大小。我们什么时候知道openfiledialog的大小发生了变化？

3）openfiledialog中用户选择的文件发生了变化，我们需要知道新选择的文件路径，用来显示在.net控件中。我们怎么知道选择了什么文件？（这里选择文件指用户用鼠标在openfiledialog中单击选取，不是点击“确定”后。）

以上所有的问题，其实在一个地方都可以知道，那就是监听openfiledialog窗体的windows消息，因为一个窗体的任何一个动作都伴随着一系列的windows消息（这个可以用spy++查看）。既然这样，那么我们可以在窗体处理windows消息的回调方法中调用api方法了，也就是窗体的control.wndproc方法中。之前已经说过了，openfiledialog声明为sealed，提供的接口少之又少，我们几乎根本不可能接触到openfiledialog的wndproc，更谈不上监听windows消息，然后调用api去操作它。这时候，nativewindow该出场了，先来引用一下msdn上对nativewindow的解释：

“提供窗口句柄和窗口过程的低级封装。”

说了像没说一样，其实就是说，将一个窗口句柄与nativewindow对象绑定后，该nativewindow对象就能接收到这个窗体的所有消息。说到windows消息，我想说一下windows桌面应用程序的运行流程，其实如果看了我前一篇博客的同学应该有些了解，中基本提到了一些。为了配合本次讲解，我再次画了一张图

上图中，虚线框可以看做是一个.net中的control类对象（或者其派生类，下同，控件即窗体、窗体即控件），正常情况下，winform程序会按照1->2->3的步骤运行，当我们将control类对象的handle（就是我们常说的窗口句柄，做了一下封装）与一个nativewindow对象绑定后，程序不再按照1->2->3这样的顺序运行了，他会按照1->2-1->2-2->3这样运行，也就是说，nativewindow对象可以拦截control类对象的windows消息，我们完全可以在nativewindow中重写他的wndproc方法，像处理自己的windows消息一样去处理control类对象的消息。所以，我们就可以在nativewindow对象的wndproc中调用我们的api方法。

接下来，上代码（代码只提供大概思路）

1.扩展对话框

复制代码代码如下:

public class multiopenfiledialog 
{ 
#region fields 
private const setwindowposflags uflagshide = 
setwindowposflags.swp_noactivate | 
setwindowposflags.swp_noownerzorder | 
setwindowposflags.swp_nomove | 
setwindowposflags.swp_nosize | 
setwindowposflags.swp_hidewindow; 
#endregion 
public string filename; 
#region public methods 
public dialogresult showdialog() 
{ 
return showdialog(null); 
} 
public dialogresult showdialog(iwin32window owner) 
{ 
using (openfiledialog open = new openfiledialog()) 
{ 
medianform median = new medianform(open); 
median.show(owner); 
win32.setwindowpos(median.handle, intptr.zero, 0, 0, 0, 0, uflagshide); //隐藏中间窗体 
dialogresult dialogresult = open.showdialog(median); //将median作为openfiledialog的owner 
median.close(); 
if (dialogresult == dialogresult.ok) 
{ 
filename = open.filename; 
} 
return dialogresult; 
} 
} 
#endregion 
}

2.监听dialog的nativewindow

复制代码代码如下:

view code 
class dialognativewindow : nativewindow,idisposable 
{ 
intptr handle; //待扩展openfiledialog的句柄 
openfiledialog openfiledialog; //待扩展openfiledialog 
datagridview addcontrol; //向窗体中添加新的控件 
childcontrolnativewindow childnative; 
bool init = false; 

public dialognativewindow(intptr handle, openfiledialog openfiledialog) 
{ 
this.handle = handle; 
this.openfiledialog = openfiledialog; 
assignhandle(handle); 

//设置控件信息 
addcontrol = new datagridview(); 
addcontrol.width = 600; 
addcontrol.height = 200; 
addcontrol.datasource = null; 
} 

#region override methods 
protected override void wndproc(ref message m) 
{ 
switch (m.msg) 
{ 
case (int)msg.wm_showwindow: //窗体显示 
{ 
nativechild(); 
addcontrol(); 
break; 
} 
case (int)msg.wm_sizing: //窗体大小改变 
{ 
updatesize(); 
break; 
} 
case (int)msg.wm_windowposchanging: //窗体位置变化 
{ 
updatelocation(m); 
break; 
} 
} 
base.wndproc(ref m); 
} 
#endregion 

#region event handlers 
void childnative_selectpathchanged(stringbuilder path) 
{ 
//处理选择目录变化事件 
//... 
} 

void childnative_selectfilechanged(stringbuilder file) 
{ 
//处理选择文件变化事件 
//如果是xls文件，将其显示在datagridview控件中 
string str = file.tostring(); 
if (str.tolower().endswith(".xls")) 
{ 
oledbmanager manager = new oledbmanager(); 
if (manager.connect("provider=microsoft.jet.oledb.4.0; data source=\'" + str + "\'; extended properties='excel 8.0;'")) 
{ 
datatable tb = manager.searchtable(); 
if (tb != null) 
{ 
addcontrol.rows.clear(); 
addcontrol.columns.clear(); 
foreach (datacolumn col in tb.columns) 
{ 
addcontrol.columns.add(col.columnname, col.caption); 
} 
foreach (datarow row in tb.rows) 
{ 
object[] objs = new object[tb.columns.count]; 
for (int i = 0; i < tb.columns.count; ++i) 
{ 
objs[i] = row[i]; 
} 
addcontrol.rows.add(objs); 
} 
} 
} 
} 
else 
{ 
addcontrol.rows.clear(); 
addcontrol.columns.clear(); 
} 
} 
#endregion 

#region private methods 
private void nativechild() 
{ 
//查找openfiledialog中的子控件 
win32.enumchildwindows(handle, new win32.enumwindowscallback(windowcallback), 0); 
} 
private void addcontrol() 
{ 
//添加控件到openfiledialog界面 
win32.setparent(addcontrol.handle, handle); 
rect currentsize = new rect(); 
win32.getclientrect(handle, ref currentsize); 
addcontrol.height = (int)currentsize.height; 
addcontrol.location = new point((int)(currentsize.width - addcontrol.width), 0); 

init = true; 
} 
private void updatelocation(message m) 
{ 
if (!init) //只初始化openfiledialog的大小一次 
{ 
windowpos pos = (windowpos)marshal.ptrtostructure(m.lparam, typeof(windowpos)); 
if (pos.flags != 0 && ((pos.flags & (int)swp_flags.swp_nosize) != (int)swp_flags.swp_nosize)) 
{ 
pos.cx += addcontrol.width; //修改openfiledialog的宽度 
marshal.structuretoptr(pos, m.lparam, true); 

rect currentsize = new rect(); 
win32.getclientrect(handle, ref currentsize); 
addcontrol.height = (int)currentsize.height; 
} 
} 
} 
private void updatesize() 
{ 
rect currentsize = new rect(); 
win32.getclientrect(handle, ref currentsize); 
win32.setwindowpos(addcontrol.handle, (intptr)zorderpos.hwnd_bottom, 0, 0, (int)addcontrol.width, (int)currentsize.height, uflagssizeex); //新添加的控件与openfiledialog大小一致 
} 
private bool windowcallback(intptr handle, int lparam) 
{ 
stringbuilder wndclass = new stringbuilder(256); 
win32.getclassname(handle, wndclass, wndclass.capacity);//获取控件类名 

if (wndclass.tostring().startswith("#32770")) //找到目标控件 
{ 
childnative = new childcontrolnativewindow(handle); 
childnative.selectfilechanged += new childcontrolnativewindow.selectfilechangedeventhandler(childnative_selectfilechanged); 
childnative.selectpathchanged += new childcontrolnativewindow.selectpathchangedeventhandler(childnative_selectpathchanged); 
return true; 
} 
return true; 
} 
#endregion 

#region enums 
private const setwindowposflags uflagssizeex = 
setwindowposflags.swp_noactivate | 
setwindowposflags.swp_noownerzorder | 
setwindowposflags.swp_nomove | 
setwindowposflags.swp_asyncwindowpos | 
setwindowposflags.swp_defererase; 
private const setwindowposflags uflagssize = 
setwindowposflags.swp_noactivate | 
setwindowposflags.swp_noownerzorder | 
setwindowposflags.swp_nomove; 
private const setwindowposflags uflagshide = 
setwindowposflags.swp_noactivate | 
setwindowposflags.swp_noownerzorder | 
setwindowposflags.swp_nomove | 
setwindowposflags.swp_nosize | 
setwindowposflags.swp_hidewindow; 
#endregion 

#region idisposable 成员 

public void dispose() 
{ 
releasehandle(); //释放与openfiledialog的句柄关联 
if (childnative != null) 
{ 
childnative.selectfilechanged -= new childcontrolnativewindow.selectfilechangedeventhandler(childnative_selectfilechanged); 
childnative.selectpathchanged -= new childcontrolnativewindow.selectpathchangedeventhandler(childnative_selectpathchanged); 
childnative.dispose(); 
} 

} 

#endregion 
}

3.监听子控件的nativewindow

复制代码代码如下:

class childcontrolnativewindow : nativewindow,idisposable 
{ 
intptr handle; //需要被监听消息的子控件句柄 
public childcontrolnativewindow(intptr handle) 
{ 
this.handle = handle; 
assignhandle(handle); 
} 

#region override methods 
protected override void wndproc(ref message m) 
{ 
switch (m.msg) 
{ 
case (int)msg.wm_notify: 
ofnotify ofnotify = (ofnotify)marshal.ptrtostructure(m.lparam, typeof(ofnotify)); 
if (ofnotify.hdr.code == (uint)dialogchangestatus.cdn_selchange) //openfiledialog选择文件发生变化 
{ 
stringbuilder file = new stringbuilder(256); 
win32.sendmessage(win32.getparent(handle), (int)dialogchangeproperties.cdm_getfilepath, (int)256, file); 
if (selectfilechanged != null) 
selectfilechanged(file); //通知注册者 
} 
else if (ofnotify.hdr.code == (uint)dialogchangestatus.cdn_folderchange) //openfiledialog选择目录发生变化 
{ 
stringbuilder path = new stringbuilder(256); 
win32.sendmessage(win32.getparent(handle), (int)dialogchangeproperties.cdm_getfolderpath, (int)256, path); 
if (selectpathchanged != null) 
selectpathchanged(path); //通知注册者 
} 
break; 
} 
base.wndproc(ref m); 
} 
#endregion 

#region delegate 
public delegate void selectfilechangedeventhandler(stringbuilder file); 
public delegate void selectpathchangedeventhandler(stringbuilder path); 
#endregion 

#region events 
public event selectfilechangedeventhandler selectfilechanged; //当openfiledialog的选择文件发生变化时发生 
public event selectpathchangedeventhandler selectpathchanged; //当openfiledialog的选择目录发生变化时发生 
#endregion 

#region idisposable 成员 

public void dispose() 
{ 
releasehandle(); //终止与子控件句柄的关联 
} 

#endregion 
}

4.中间过渡窗体，用来获取openfiledialog的句柄

复制代码代码如下:

 
class medianform : form 
{ 
openfiledialog open = null; 
dialognativewindow dialognative; 

public medianform(openfiledialog open) 
{ 
this.open = open; 
startposition = formstartposition.manual; 
location = new system.drawing.point(-1000, -1000); //避免界面闪烁 
} 
protected override void onclosing(system.componentmodel.canceleventargs e) 
{ 
if (dialognative != null) 
{ 
dialognative.dispose(); //释放资源 
} 
base.onclosing(e); 
} 
protected override void wndproc(ref message m) 
{ 
if (m.msg == (int) msg.wm_activate) 
{ 
dialognative = new dialognativewindow(m.lparam, open); //m.lparam为要打开的窗口句柄，开始监听openfiledialog的windows消息 
} 
base.wndproc(ref m); 
} 
}

5.访问excel文件的类

复制代码代码如下:

class oledbmanager 
{ 
oledbconnection conn; 
/// <summary> 
/// 连接excel文件 
/// </summary> 
/// <param name="connstr"></param> 
/// <returns></returns> 
public bool connect(string connstr) 
{ 
try 
{ 
conn = new oledbconnection(connstr); 
conn.open(); 
return true; 
} 
catch 
{ 
return false; 
} 
} 
/// <summary> 
/// 查找第一张表中的数据 
/// </summary> 
/// <returns></returns> 
public datatable searchtable() 
{ 
try 
{ 
datatable tb = new datatable(); 
string sql = "select * from [sheet1$]"; 
oledbcommand com = new oledbcommand(sql, conn); 
oledbdataadapter adp = new oledbdataadapter(com); 
adp.fill(tb); 
return tb; 
} 
catch 
{ 
return null; 
} 
} 
}

6.几个win32结构体、枚举类型以及api声明（本代码参考codeproject上的一篇文章）

复制代码代码如下:

public static class win32 
{ 
#region delegates 
public delegate bool enumwindowscallback(intptr hwnd, int lparam); 
#endregion 

#region user32 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern intptr getparent(intptr hwnd); 
[dllimport("user32.dll")] 
public static extern int getdlgctrlid(intptr hwndctl); 
[dllimport("user32.dll", charset = charset.auto, exactspelling = true)] 
public static extern int mapwindowpoints(intptr hwnd, intptr hwndto, ref point pt, int cpoints); 
[dllimport("user32.dll", setlasterror = true)] 
public static extern bool getwindowinfo(intptr hwnd, out windowinfo pwi); 
[dllimport("user32.dll")] 
public static extern void getwindowtext(intptr hwnd, stringbuilder param, int length); 
[dllimport("user32.dll")] 
public static extern void getclassname(intptr hwnd, stringbuilder param, int length); 
[dllimport("user32.dll")] 
public static extern bool enumchildwindows(intptr hwndparent, enumwindowscallback lpenumfunc, int lparam); 
[dllimport("user32.dll")] 
public static extern bool enumwindows(enumwindowscallback lpenumfunc, int lparam); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern bool releasecapture(); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern intptr setcapture(intptr hwnd); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern intptr childwindowfrompointex(intptr hparent, point pt, childfrompointflags flags); 
[dllimport("user32.dll", entrypoint = "findwindowexa", callingconvention = callingconvention.stdcall, charset = charset.ansi)] 
public static extern intptr findwindowex(intptr hwndparent, intptr hwndchildafter, string lpszclass, string lpszwindow); 
[dllimport("user32.dll")] 
public static extern intptr setparent(intptr hwndchild, intptr hwndnewparent); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern int postmessage(intptr hwnd, uint msg, intptr wparam, intptr lparam); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern int postmessage(intptr hwnd, int msg, int wparam, int lparam); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern int sendmessage(intptr hwnd, uint msg, intptr wparam, intptr lparam); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern int sendmessage(intptr hwnd, int msg, int wparam, int lparam); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern int sendmessage(intptr hwnd, int msg, int wparam, stringbuilder param); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern int sendmessage(intptr hwnd, int msg, int wparam, char[] chars); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern intptr begindeferwindowpos(int nnumwindows); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern intptr deferwindowpos(intptr hwinposinfo, intptr hwnd, intptr hwndinsertafter, int x, int y, int width, int height, setwindowposflags flags); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern bool enddeferwindowpos(intptr hwinposinfo); 
[dllimport("user32.dll", charset = charset.auto)] 
public static extern bool setwindowpos(intptr hwnd, intptr hwndinsertafter, int x, int y, int width, int height, setwindowposflags flags); 
[dllimport("user32.dll")] 
public static extern bool getwindowrect(intptr hwnd, ref rect rect); 
[dllimport("user32.dll")] 
public static extern bool getclientrect(intptr hwnd, ref rect rect); 
#endregion 
} 
#region swp_flags 
[flags] 
public enum swp_flags 
{ 
swp_nosize = 0x0001, 
swp_nomove = 0x0002, 
swp_nozorder = 0x0004, 
swp_noactivate = 0x0010, 
swp_framechanged = 0x0020, /* the frame changed: send wm_nccalcsize */ 
swp_showwindow = 0x0040, 
swp_hidewindow = 0x0080, 
swp_noownerzorder = 0x0200, /* don't do owner z ordering */ 

swp_drawframe = swp_framechanged, 
swp_noreposition = swp_noownerzorder 
} 
#endregion 

#region dialogchangestatus 
public enum dialogchangestatus : long 
{ 
cdn_first = 0xfffffda7, 
cdn_initdone = (cdn_first - 0x0000), 
cdn_selchange = (cdn_first - 0x0001), 
cdn_folderchange = (cdn_first - 0x0002), 
cdn_shareviolation = (cdn_first - 0x0003), 
cdn_help = (cdn_first - 0x0004), 
cdn_fileok = (cdn_first - 0x0005), 
cdn_typechange = (cdn_first - 0x0006), 
} 
#endregion 

#region dialogchangeproperties 
public enum dialogchangeproperties 
{ 
cdm_first = (0x400 + 100), 
cdm_getspec = (cdm_first + 0x0000), 
cdm_getfilepath = (cdm_first + 0x0001), 
cdm_getfolderpath = (cdm_first + 0x0002), 
cdm_getfolderidlist = (cdm_first + 0x0003), 
cdm_setcontroltext = (cdm_first + 0x0004), 
cdm_hidecontrol = (cdm_first + 0x0005), 
cdm_setdefext = (cdm_first + 0x0006) 
} 
#endregion 

#region imenotify 
public enum imenotify 
{ 
imn_closestatuswindow = 0x0001, 
imn_openstatuswindow = 0x0002, 
imn_changecandidate = 0x0003, 
imn_closecandidate = 0x0004, 
imn_opencandidate = 0x0005, 
imn_setconversionmode = 0x0006, 
imn_setsentencemode = 0x0007, 
imn_setopenstatus = 0x0008, 
imn_setcandidatepos = 0x0009, 
imn_setcompositionfont = 0x000a, 
imn_setcompositionwindow = 0x000b, 
imn_setstatuswindowpos = 0x000c, 
imn_guideline = 0x000d, 
imn_private = 0x000e 
} 
#endregion 

#region folderviewmode 
public enum folderviewmode 
{ 
default = 0x7028, 
icon = default + 1, 
smallicon = default + 2, 
list = default + 3, 
details = default + 4, 
thumbnails = default + 5, 
title = default + 6, 
thumbstrip = default + 7, 
} 
#endregion 

#region enum dialogviewproperty 
public enum defaultviewtype 
{ 
icons = 0x7029, 
list = 0x702b, 
details = 0x702c, 
thumbnails = 0x702d, 
tiles = 0x702e, 
} 
#endregion 

#region buttonstyle 
public enum buttonstyle : long 
{ 
bs_pushbutton = 0x00000000, 
bs_defpushbutton = 0x00000001, 
bs_checkbox = 0x00000002, 
bs_autocheckbox = 0x00000003, 
bs_radiobutton = 0x00000004, 
bs_3state = 0x00000005, 
bs_auto3state = 0x00000006, 
bs_groupbox = 0x00000007, 
bs_userbutton = 0x00000008, 
bs_autoradiobutton = 0x00000009, 
bs_pushbox = 0x0000000a, 
bs_ownerdraw = 0x0000000b, 
bs_typemask = 0x0000000f, 
bs_lefttext = 0x00000020, 
bs_text = 0x00000000, 
bs_icon = 0x00000040, 
bs_bitmap = 0x00000080, 
bs_left = 0x00000100, 
bs_right = 0x00000200, 
bs_center = 0x00000300, 
bs_top = 0x00000400, 
bs_bottom = 0x00000800, 
bs_vcenter = 0x00000c00, 
bs_pushlike = 0x00001000, 
bs_multiline = 0x00002000, 
bs_notify = 0x00004000, 
bs_flat = 0x00008000, 
bs_rightbutton = bs_lefttext 
} 
#endregion 

#region zorderpos 
public enum zorderpos 
{ 
hwnd_top = 0, 
hwnd_bottom = 1, 
hwnd_topmost = -1, 
hwnd_notopmost = -2 
} 
#endregion 

#region static control styles 
public enum staticcontrolstyles : long 
{ 
ss_left = 0x00000000, 
ss_center = 0x00000001, 
ss_right = 0x00000002, 
ss_icon = 0x00000003, 
ss_blackrect = 0x00000004, 
ss_grayrect = 0x00000005, 
ss_whiterect = 0x00000006, 
ss_blackframe = 0x00000007, 
ss_grayframe = 0x00000008, 
ss_whiteframe = 0x00000009, 
ss_useritem = 0x0000000a, 
ss_simple = 0x0000000b, 
ss_leftnowordwrap = 0x0000000c, 
ss_ownerdraw = 0x0000000d, 
ss_bitmap = 0x0000000e, 
ss_enhmetafile = 0x0000000f, 
ss_etchedhorz = 0x00000010, 
ss_etchedvert = 0x00000011, 
ss_etchedframe = 0x00000012, 
ss_typemask = 0x0000001f, 
ss_realsizecontrol = 0x00000040, 
ss_noprefix = 0x00000080, /* don't do "&" character translation */ 
ss_notify = 0x00000100, 
ss_centerimage = 0x00000200, 
ss_rightjust = 0x00000400, 
ss_realsizeimage = 0x00000800, 
ss_sunken = 0x00001000, 
ss_editcontrol = 0x00002000, 
ss_endellipsis = 0x00004000, 
ss_pathellipsis = 0x00008000, 
ss_wordellipsis = 0x0000c000, 
ss_ellipsismask = 0x0000c000 
} 
#endregion 

#region combo box styles 
public enum comboboxstyles : long 
{ 
cbs_simple = 0x0001, 
cbs_dropdown = 0x0002, 
cbs_dropdownlist = 0x0003, 
cbs_ownerdrawfixed = 0x0010, 
cbs_ownerdrawvariable = 0x0020, 
cbs_autohscroll = 0x0040, 
cbs_oemconvert = 0x0080, 
cbs_sort = 0x0100, 
cbs_hasstrings = 0x0200, 
cbs_nointegralheight = 0x0400, 
cbs_disablenoscroll = 0x0800, 
cbs_uppercase = 0x2000, 
cbs_lowercase = 0x4000 
} 
#endregion 

#region window styles 
public enum windowstyles : long 
{ 
ws_overlapped = 0x00000000, 
ws_popup = 0x80000000, 
ws_child = 0x40000000, 
ws_minimize = 0x20000000, 
ws_visible = 0x10000000, 
ws_disabled = 0x08000000, 
ws_clipsiblings = 0x04000000, 
ws_clipchildren = 0x02000000, 
ws_maximize = 0x01000000, 
ws_caption = 0x00c00000, 
ws_border = 0x00800000, 
ws_dlgframe = 0x00400000, 
ws_vscroll = 0x00200000, 
ws_hscroll = 0x00100000, 
ws_sysmenu = 0x00080000, 
ws_thickframe = 0x00040000, 
ws_group = 0x00020000, 
ws_tabstop = 0x00010000, 
ws_minimizebox = 0x00020000, 
ws_maximizebox = 0x00010000, 
ws_tiled = 0x00000000, 
ws_iconic = 0x20000000, 
ws_sizebox = 0x00040000, 
ws_popupwindow = 0x80880000, 
ws_overlappedwindow = 0x00cf0000, 
ws_tiledwindow = 0x00cf0000, 
ws_childwindow = 0x40000000 
} 
#endregion 

#region window extended styles 
public enum windowexstyles 
{ 
ws_ex_dlgmodalframe = 0x00000001, 
ws_ex_noparentnotify = 0x00000004, 
ws_ex_topmost = 0x00000008, 
ws_ex_acceptfiles = 0x00000010, 
ws_ex_transparent = 0x00000020, 
ws_ex_mdichild = 0x00000040, 
ws_ex_toolwindow = 0x00000080, 
ws_ex_windowedge = 0x00000100, 
ws_ex_clientedge = 0x00000200, 
ws_ex_contexthelp = 0x00000400, 
ws_ex_right = 0x00001000, 
ws_ex_left = 0x00000000, 
ws_ex_rtlreading = 0x00002000, 
ws_ex_ltrreading = 0x00000000, 
ws_ex_leftscrollbar = 0x00004000, 
ws_ex_rightscrollbar = 0x00000000, 
ws_ex_controlparent = 0x00010000, 
ws_ex_staticedge = 0x00020000, 
ws_ex_appwindow = 0x00040000, 
ws_ex_overlappedwindow = 0x00000300, 
ws_ex_palettewindow = 0x00000188, 
ws_ex_layered = 0x00080000 
} 
#endregion 

#region childfrompointflags 
public enum childfrompointflags 
{ 
cwp_all = 0x0000, 
cwp_skipinvisible = 0x0001, 
cwp_skipdisabled = 0x0002, 
cwp_skiptransparent = 0x0004 
} 
#endregion 

#region hittest 
public enum hittest 
{ 
hterror = (-2), 
httransparent = (-1), 
htnowhere = 0, 
htclient = 1, 
htcaption = 2, 
htsysmenu = 3, 
htgrowbox = 4, 
htsize = htgrowbox, 
htmenu = 5, 
hthscroll = 6, 
htvscroll = 7, 
htminbutton = 8, 
htmaxbutton = 9, 
htleft = 10, 
htright = 11, 
httop = 12, 
httopleft = 13, 
httopright = 14, 
htbottom = 15, 
htbottomleft = 16, 
htbottomright = 17, 
htborder = 18, 
htreduce = htminbutton, 
htzoom = htmaxbutton, 
htsizefirst = htleft, 
htsizelast = htbottomright, 
htobject = 19, 
htclose = 20, 
hthelp = 21 
} 
#endregion 

#region windows messages 
public enum msg 
{ 
wm_null = 0x0000, 
wm_create = 0x0001, 
wm_destroy = 0x0002, 
wm_move = 0x0003, 
wm_size = 0x0005, 
wm_activate = 0x0006, 
wm_setfocus = 0x0007, 
wm_killfocus = 0x0008, 
wm_enable = 0x000a, 
wm_setredraw = 0x000b, 
wm_settext = 0x000c, 
wm_gettext = 0x000d, 
wm_gettextlength = 0x000e, 
wm_paint = 0x000f, 
wm_close = 0x0010, 
wm_queryendsession = 0x0011, 
wm_quit = 0x0012, 
wm_queryopen = 0x0013, 
wm_erasebkgnd = 0x0014, 
wm_syscolorchange = 0x0015, 
wm_endsession = 0x0016, 
wm_showwindow = 0x0018, 
wm_ctlcolor = 0x0019, 
wm_wininichange = 0x001a, 
wm_settingchange = 0x001a, 
wm_devmodechange = 0x001b, 
wm_activateapp = 0x001c, 
wm_fontchange = 0x001d, 
wm_timechange = 0x001e, 
wm_cancelmode = 0x001f, 
wm_setcursor = 0x0020, 
wm_mouseactivate = 0x0021, 
wm_childactivate = 0x0022, 
wm_queuesync = 0x0023, 
wm_getminmaxinfo = 0x0024, 
wm_painticon = 0x0026, 
wm_iconerasebkgnd = 0x0027, 
wm_nextdlgctl = 0x0028, 
wm_spoolerstatus = 0x002a, 
wm_drawitem = 0x002b, 
wm_measureitem = 0x002c, 
wm_deleteitem = 0x002d, 
wm_vkeytoitem = 0x002e, 
wm_chartoitem = 0x002f, 
wm_setfont = 0x0030, 
wm_getfont = 0x0031, 
wm_sethotkey = 0x0032, 
wm_gethotkey = 0x0033, 
wm_querydragicon = 0x0037, 
wm_compareitem = 0x0039, 
wm_getobject = 0x003d, 
wm_compacting = 0x0041, 
wm_commnotify = 0x0044, 
wm_windowposchanging = 0x0046, 
wm_windowposchanged = 0x0047, 
wm_power = 0x0048, 
wm_copydata = 0x004a, 
wm_canceljournal = 0x004b, 
wm_notify = 0x004e, 
wm_inputlangchangerequest = 0x0050, 
wm_inputlangchange = 0x0051, 
wm_tcard = 0x0052, 
wm_help = 0x0053, 
wm_userchanged = 0x0054, 
wm_notifyformat = 0x0055, 
wm_contextmenu = 0x007b, 
wm_stylechanging = 0x007c, 
wm_stylechanged = 0x007d, 
wm_displaychange = 0x007e, 
wm_geticon = 0x007f, 
wm_seticon = 0x0080, 
wm_nccreate = 0x0081, 
wm_ncdestroy = 0x0082, 
wm_nccalcsize = 0x0083, 
wm_nchittest = 0x0084, 
wm_ncpaint = 0x0085, 
wm_ncactivate = 0x0086, 
wm_getdlgcode = 0x0087, 
wm_syncpaint = 0x0088, 
wm_ncmousemove = 0x00a0, 
wm_nclbuttondown = 0x00a1, 
wm_nclbuttonup = 0x00a2, 
wm_nclbuttondblclk = 0x00a3, 
wm_ncrbuttondown = 0x00a4, 
wm_ncrbuttonup = 0x00a5, 
wm_ncrbuttondblclk = 0x00a6, 
wm_ncmbuttondown = 0x00a7, 
wm_ncmbuttonup = 0x00a8, 
wm_ncmbuttondblclk = 0x00a9, 
wm_ncxbuttondown = 0x00ab, 
wm_ncxbuttonup = 0x00ac, 
wm_ncxbuttondblclk = 0x00ad, 
wm_keydown = 0x0100, 
wm_keyup = 0x0101, 
wm_char = 0x0102, 
wm_deadchar = 0x0103, 
wm_syskeydown = 0x0104, 
wm_syskeyup = 0x0105, 
wm_syschar = 0x0106, 
wm_sysdeadchar = 0x0107, 
wm_keylast = 0x0108, 
wm_ime_startcomposition = 0x010d, 
wm_ime_endcomposition = 0x010e, 
wm_ime_composition = 0x010f, 
wm_ime_keylast = 0x010f, 
wm_initdialog = 0x0110, 
wm_command = 0x0111, 
wm_syscommand = 0x0112, 
wm_timer = 0x0113, 
wm_hscroll = 0x0114, 
wm_vscroll = 0x0115, 
wm_initmenu = 0x0116, 
wm_initmenupopup = 0x0117, 
wm_menuselect = 0x011f, 
wm_menuchar = 0x0120, 
wm_enteridle = 0x0121, 
wm_menurbuttonup = 0x0122, 
wm_menudrag = 0x0123, 
wm_menugetobject = 0x0124, 
wm_uninitmenupopup = 0x0125, 
wm_menucommand = 0x0126, 
wm_ctlcolormsgbox = 0x0132, 
wm_ctlcoloredit = 0x0133, 
wm_ctlcolorlistbox = 0x0134, 
wm_ctlcolorbtn = 0x0135, 
wm_ctlcolordlg = 0x0136, 
wm_ctlcolorscrollbar = 0x0137, 
wm_ctlcolorstatic = 0x0138, 
wm_mousemove = 0x0200, 
wm_lbuttondown = 0x0201, 
wm_lbuttonup = 0x0202, 
wm_lbuttondblclk = 0x0203, 
wm_rbuttondown = 0x0204, 
wm_rbuttonup = 0x0205, 
wm_rbuttondblclk = 0x0206, 
wm_mbuttondown = 0x0207, 
wm_mbuttonup = 0x0208, 
wm_mbuttondblclk = 0x0209, 
wm_mousewheel = 0x020a, 
wm_xbuttondown = 0x020b, 
wm_xbuttonup = 0x020c, 
wm_xbuttondblclk = 0x020d, 
wm_parentnotify = 0x0210, 
wm_entermenuloop = 0x0211, 
wm_exitmenuloop = 0x0212, 
wm_nextmenu = 0x0213, 
wm_sizing = 0x0214, 
wm_capturechanged = 0x0215, 
wm_moving = 0x0216, 
wm_devicechange = 0x0219, 
wm_mdicreate = 0x0220, 
wm_mdidestroy = 0x0221, 
wm_mdiactivate = 0x0222, 
wm_mdirestore = 0x0223, 
wm_mdinext = 0x0224, 
wm_mdimaximize = 0x0225, 
wm_mditile = 0x0226, 
wm_mdicascade = 0x0227, 
wm_mdiiconarrange = 0x0228, 
wm_mdigetactive = 0x0229, 
wm_mdisetmenu = 0x0230, 
wm_entersizemove = 0x0231, 
wm_exitsizemove = 0x0232, 
wm_dropfiles = 0x0233, 
wm_mdirefreshmenu = 0x0234, 
wm_ime_setcontext = 0x0281, 
wm_ime_notify = 0x0282, 
wm_ime_control = 0x0283, 
wm_ime_compositionfull = 0x0284, 
wm_ime_select = 0x0285, 
wm_ime_char = 0x0286, 
wm_ime_request = 0x0288, 
wm_ime_keydown = 0x0290, 
wm_ime_keyup = 0x0291, 
wm_mousehover = 0x02a1, 
wm_mouseleave = 0x02a3, 
wm_cut = 0x0300, 
wm_copy = 0x0301, 
wm_paste = 0x0302, 
wm_clear = 0x0303, 
wm_undo = 0x0304, 
wm_renderformat = 0x0305, 
wm_renderallformats = 0x0306, 
wm_destroyclipboard = 0x0307, 
wm_drawclipboard = 0x0308, 
wm_paintclipboard = 0x0309, 
wm_vscrollclipboard = 0x030a, 
wm_sizeclipboard = 0x030b, 
wm_askcbformatname = 0x030c, 
wm_changecbchain = 0x030d, 
wm_hscrollclipboard = 0x030e, 
wm_querynewpalette = 0x030f, 
wm_paletteischanging = 0x0310, 
wm_palettechanged = 0x0311, 
wm_hotkey = 0x0312, 
wm_print = 0x0317, 
wm_printclient = 0x0318, 
wm_theme_changed = 0x031a, 
wm_handheldfirst = 0x0358, 
wm_handheldlast = 0x035f, 
wm_afxfirst = 0x0360, 
wm_afxlast = 0x037f, 
wm_penwinfirst = 0x0380, 
wm_penwinlast = 0x038f, 
wm_app = 0x8000, 
wm_user = 0x0400, 
wm_reflect = wm_user + 0x1c00 
} 
#endregion 

#region setwindowposflags 
public enum setwindowposflags 
{ 
swp_nosize = 0x0001, 
swp_nomove = 0x0002, 
swp_nozorder = 0x0004, 
swp_noredraw = 0x0008, 
swp_noactivate = 0x0010, 
swp_framechanged = 0x0020, 
swp_showwindow = 0x0040, 
swp_hidewindow = 0x0080, 
swp_nocopybits = 0x0100, 
swp_noownerzorder = 0x0200, 
swp_nosendchanging = 0x0400, 
swp_drawframe = 0x0020, 
swp_noreposition = 0x0200, 
swp_defererase = 0x2000, 
swp_asyncwindowpos = 0x4000 
} 
#endregion 
} 

#region windowinfo 
[structlayout(layoutkind.sequential)] 
public struct windowinfo 
{ 
public uint32 cbsize; 
public rect rcwindow; 
public rect rcclient; 
public uint32 dwstyle; 
public uint32 dwexstyle; 
public uint32 dwwindowstatus; 
public uint32 cxwindowborders; 
public uint32 cywindowborders; 
public uint16 atomwindowtype; 
public uint16 wcreatorversion; 
} 
#endregion 

#region point 
[structlayout(layoutkind.sequential)] 
public struct point 
{ 
public int x; 
public int y; 

#region constructors 
public point(int x, int y) 
{ 
this.x = x; 
this.y = y; 
} 

public point(point point) 
{ 
x = point.x; 
y = point.y; 
} 
#endregion 
} 
#endregion 

#region rect 
[structlayout(layoutkind.sequential)] 
public struct rect 
{ 
public uint left; 
public uint top; 
public uint right; 
public uint bottom; 

#region properties 
public point location 
{ 
get { return new point((int)left, (int)top); } 
set 
{ 
right -= (left - (uint)value.x); 
bottom -= (bottom - (uint)value.y); 
left = (uint)value.x; 
top = (uint)value.y; 
} 
} 

public uint width 
{ 
get { return right - left; } 
set { right = left + value; } 
} 

public uint height 
{ 
get { return bottom - top; } 
set { bottom = top + value; } 
} 
#endregion 

#region overrides 
public override string tostring() 
{ 
return left + ":" + top + ":" + right + ":" + bottom; 
} 
#endregion 
} 
#endregion 

#region windowpos 
[structlayout(layoutkind.sequential)] 
public struct windowpos 
{ 
public intptr hwnd; 
public intptr hwndafter; 
public int x; 
public int y; 
public int cx; 
public int cy; 
public uint flags; 

#region overrides 
public override string tostring() 
{ 
return x + ":" + y + ":" + cx + ":" + cy + ":" + ((swp_flags)flags).tostring(); 
} 
#endregion 
} 
#endregion 

#region nccalcsize_params 
[structlayout(layoutkind.sequential)] 
public struct nccalcsize_params 
{ 
public rect rgrc1; 
public rect rgrc2; 
public rect rgrc3; 
public intptr lppos; 
} 
#endregion 

#region nmhdr 
[structlayout(layoutkind.sequential)] 
public struct nmhdr 
{ 
public intptr hwndfrom; 
public uint idfrom; 
public uint code; 
} 
#endregion 

#region ofnotify 
[structlayout(layoutkind.sequential)] 
public struct ofnotify 
{ 
public nmhdr hdr; 
public intptr openfilename; 
public intptr filenameshareviolation; 
} 
#endregion

补充一下
1.代码只提供思路，不能拿来继承一下，就能实现自己想要的功能。

2.可以自己将代码中dialognativewindow类的addcontrol替换为其他控件，比如picturebox用来预览图片、textbox用来预览txt文件、richtextbox用来预览代码文件等等，还可自由组合。

3.可以自己将代码中dialognativewindow类的两个事件（selectedfilechanged、selectpathchanged）移到multiopenfiledialog中，并使其对外开放，外部程序可以监听该事件。

4.如果想做成通用类，拿过来继承一下就可以实现自己想要的效果，建议使multiopenfiledialog从usercontrol，并将addcontrol设为自己。也就是说将自己添加到openfiledialog中去，multiopenfiledialog的派生类就可以在vs中设计自己想要的效果。

5.一个窗体新建显示时，它的拥有者会接收许多消息，包括wm_activate、wm_idle等等，并且lparam参数为新建窗体的句柄。

复制代码代码如下:

 
class form1:form 
{ 
private void form1_load(object sender,eventargs e) 
{ 
using(openfiledialog dia = new openfiledialog()) 
{ 
dia.showdialog(this); 
} 
} 
protected override void wndproc(ref message m) 
{ 
//当dia显示时，它的拥有者即为this，这里会接受一连串的window消息，并且它的lparam参数为dia的句柄 
base.wndproc(ref m); 
} 
}

6.windows中窗体和所谓的控件（button、textbox）本质上没有区别，任务栏与qq聊天框或者chrome浏览器的地址栏对我们程序员来讲，是同一个东西。

7.与窗体有关的win32 api基本都需要窗体句柄，其实任何一个api几乎都需要知道操作对象的句柄（不一定是窗体）。

8.windows中任何一个窗体（控件）理论上都是平级的，不管是否同一进程，也就是说，我的winform应用程序只要知道了chrome浏览器窗体的句柄，就可以控制chrome浏览器，监听chrome窗体的windows消息（除非chrome程序本身禁止了此操作）。

9.windows桌面应用程序开发中，（部分平台、语言）理解四个东西，即进程、线程、窗体（已经说了，是广义上的窗体）、消息。

10.查看系统中以上四个东西，可以使用spy++工具。

完了，剩下那个下次再写了，太多了。希望有帮助~