调用外部dll

public class DllInvoke
{
[DllImport("kernel32.dll")]
private extern static IntPtr LoadLibrary(String path);
[DllImport("kernel32.dll")]
private extern static IntPtr LoadModule(String path);
[DllImport("kernel32.dll")]
private extern static IntPtr GetProcAddress(IntPtr lib, String funcName);
[DllImport("kernel32.dll")]
private extern static bool FreeLibrary(IntPtr lib);
public IntPtr hLib;
public DllInvoke(String DLLPath)
{
//hLib = LoadLibrary(DLLPath);
hLib = LoadLibrary(DLLPath);
//hLib = (IntPtr)268435456;
}
~DllInvoke()
{
FreeLibrary(hLib);
}
//将要执行的函数转换为委托
public Delegate Invoke(String APIName, Type t)
{
IntPtr api = GetProcAddress(hLib, APIName);
return (Delegate)Marshal.GetDelegateForFunctionPointer(api, t);//.NET 2.0新增了Marshal.GetDelegateForFunctionPointer 方法可以满足这个要求，MSDN里的解释是：将非托管函数指针转换为委托
}
}

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然后程序就可以声明函数内部方法，进行调用