P/Invoke
P/Invoke
1.P/Invoke是什么?有何作用?
2.简单的使用P/Invoke的demo
1.P/Invoke是什么?有何作用?
P/Invoke使得C#程序调用非托管的成为可能,例如可以使用P/Invoke来调用win32 api。
2.简单的使用P/Invoke的demo
2.1 使用P/Invoke直接调用win32 api
public class Program
{
/// <summary>
/// import kernel32.dll
/// </summary>
/// <param name="source"></param>
/// <param name="dest"></param>
/// <returns></returns>
[DllImport("kernel32.dll", EntryPoint = "MoveFile",
ExactSpelling = false,
CharSet = CharSet.Unicode,
SetLastError = true)]
static extern bool MoveFile(string source, string dest);
static void Main(string[] args)
{
// Call P/Invoke
string source = @"d:\test.txt";
string dest = @"d:\test.txt.bak";
if (UsingPInvoke.Program.MoveFile(source, dest) == true)
{
Console.WriteLine("Move File Ok!");
}
else
{
Console.WriteLine("Move File Error!");
}
}
{
/// <summary>
/// import kernel32.dll
/// </summary>
/// <param name="source"></param>
/// <param name="dest"></param>
/// <returns></returns>
[DllImport("kernel32.dll", EntryPoint = "MoveFile",
ExactSpelling = false,
CharSet = CharSet.Unicode,
SetLastError = true)]
static extern bool MoveFile(string source, string dest);
static void Main(string[] args)
{
// Call P/Invoke
string source = @"d:\test.txt";
string dest = @"d:\test.txt.bak";
if (UsingPInvoke.Program.MoveFile(source, dest) == true)
{
Console.WriteLine("Move File Ok!");
}
else
{
Console.WriteLine("Move File Error!");
}
}
}
2.2 C#中的指针
public class UsingPointers
{
const uint GenericRead = 0x80000000;
const uint OpenExisting = 3;
const uint UseDefault = 0;
int fileHandle;
[DllImport("kernel32.dll",
SetLastError = true)]
static extern unsafe int CreateFile(
string filename,
uint desiredAccess,
uint shareMode,
uint attributes,
uint createDisposition,
uint flagsAndAttributes,
uint templateFile
);
[DllImport("kernel32.dll",
SetLastError = true)]
static extern unsafe bool ReadFile(
int hFile,
void* lpBuffer,
int bBytesToRead,
int* nBytesRead,
int overlapped
);
public UsingPointers(string filename)
{
this.fileHandle = CreateFile(
filename,
GenericRead,
UseDefault,
UseDefault,
OpenExisting,
UseDefault,
UseDefault
);
}
public unsafe int Read(byte[] buffer, int index, int count)
{
int byteRead = 0;
// 将byte[]转换成byte*
fixed(byte* bytePointer = buffer)
{
// 调用win32函数
ReadFile(
fileHandle,
bytePointer + index,
count,
&byteRead,
0
);
}
return byteRead;
}
}
{
const uint GenericRead = 0x80000000;
const uint OpenExisting = 3;
const uint UseDefault = 0;
int fileHandle;
[DllImport("kernel32.dll",
SetLastError = true)]
static extern unsafe int CreateFile(
string filename,
uint desiredAccess,
uint shareMode,
uint attributes,
uint createDisposition,
uint flagsAndAttributes,
uint templateFile
);
[DllImport("kernel32.dll",
SetLastError = true)]
static extern unsafe bool ReadFile(
int hFile,
void* lpBuffer,
int bBytesToRead,
int* nBytesRead,
int overlapped
);
public UsingPointers(string filename)
{
this.fileHandle = CreateFile(
filename,
GenericRead,
UseDefault,
UseDefault,
OpenExisting,
UseDefault,
UseDefault
);
}
public unsafe int Read(byte[] buffer, int index, int count)
{
int byteRead = 0;
// 将byte[]转换成byte*
fixed(byte* bytePointer = buffer)
{
// 调用win32函数
ReadFile(
fileHandle,
bytePointer + index,
count,
&byteRead,
0
);
}
return byteRead;
}
}
注意编译时,需要更改项目属性:
下面是一个p/invoke的具体例子,通过p/invoke来播放wav文件:http://www.codeproject.com/Articles/175030/PlaySound-A-Better-Way-to-Play-Wav-Files-in-Csharp.aspx
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