转自:http://hacker.cnblogs.com/archive/2004/08/12/32563.aspx
1, PInvoke什么意思? Platform Invocation Services
2, 干什么用? 导入外部函数?什么是外部函数,就是不属于.Net托管的函数。
3,如何用?看下面的例子。用[DllImport(dllname)]来实现,但是首先要把System.Runtiime.InteropServices using进来。但是不using也行,就要敲全称,随你便了。
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4,万一我的程序中已经有了一个函数叫MessageBoxA怎么办?这时候,可以使用EntryPoint来帮忙,下面的例子中,你把自己的函数定义为MyMsg.
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5,charset如何使用?****A的是Ansi编码,****W的是unicode编码,如何使用charset,看你的函数调用而定。2K以后都用unicode了,前面的9x都是ansi编码,但是这是缺省的,微软给9x打布丁支持unicode不算。
API有两个版本: A(ASNI)版本和W(Unicode)版本. A版本调用时候会用ANSI来封送字符串,一般是win95/98上。W版本用Unicode来封送,在NT,2K和XP上。
.Net和win32交互的时候,默认是使用CharSet.Ansi来传送。
在
当 ExactSpelling 字段为 false(它是 C++ 托管扩展和 C# 中的默认值),平台调用将首先搜索未处理的别名 (MessageBox),如果没有找到未处理的别名,则将搜索已处理的名称 (MessageBoxA)。请注意,ANSI 名称匹配行为与 Unicode 名称匹配行为不同。
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6,Dll里面的callback函数如何实现?看下面这个例子:
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7,MarshalAs如何用,什么时候用?
在MessageBox传递string去Dll的时,C#编译器知道Win32LPSTR等价与一个C#字符串。但是如果想覆盖默认.Net行为, 这时候就需要MarshallAs
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8,我怎么知道要调用的函数在那个dll了?
这个问题我不会比你更清楚,特殊的函数应该在你特殊的dll中。Win32中常用的几个dll是user32.dll, kernel32.dll和GDI32.dll.用dumpbin -exports kernel32.dll可以看到这个dll所有的API函数。
9,相互之间传递struct怎么办?我是说传递很复杂的struct?
传递一个结构,这个要用到StructLayoutAttribute属性。比如:
PtInRect 具有以下非托管签名:
BOOL PtInRect(const RECT *lprc, POINT pt);
请注意,由于函数需要指向 RECT 类型的指针,必须通过引用来传递 Rect 结构。
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10,哪里有不错的教程,我可以学到更详细的东西?
google一下多的是。MSDN里面也有一些不错的教程:(vs.net 2003)
11,最后,这位大哥,你说了很多,我想问一个对我来说最关键的问题,我看了你的东西,似是而非,不会用怎么办?
这位兄弟勇气可嘉,我给你准备了一个站点。这里有一个PInvoke的Add-In tools for Visual Studio.Net,几乎所有的Win32 API都有。安装了以后,基本不用自己写了。