using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Runtime.InteropServices; 
 
namespace ConsoleApplication1 
{ 
        public class DLLWrapper 
        { 
                ///<summary>    
                ///API LoadLibrary    
                ///</summary>    
                [DllImport("Kernel32")] 
                public static extern int LoadLibrary(String funcname); 
 
                ///<summary>    
                ///API GetProcAddress    
                ///</summary>    
                [DllImport("Kernel32")] 
                public static extern int GetProcAddress(int handle, String funcname); 
                ///<summary>    
                ///API FreeLibrary    
                ///</summary>    
                [DllImport("Kernel32")] 
                public static extern int FreeLibrary(int handle); 
                ///<summary>    
                ///通过非托管函数名转换为对应的委托

                ///</summary>    
                ///<param name="dllModule">通过LoadLibrary获得的DLL句柄</param>    
                ///<param name="functionName">非托管函数名</param>    
                ///<param name="t">对应的委托类型</param>    
                ///<returns>委托实例，可强制转换为适当的委托类型</returns>    
                public static Delegate GetFunctionAddress(int dllModule, string functionName, Type t) 
                { 
                        int address = GetProcAddress(dllModule, functionName); 
                        if (address == 0) 
                                return null; 
                        else 
                                return Marshal.GetDelegateForFunctionPointer(new IntPtr(address), t); 
                } 
 
                ///<summary>    
                ///将表示函数地址的IntPtr实例转换成对应的委托                ///</summary>    
                public static Delegate GetDelegateFromIntPtr(IntPtr address, Type t) 
                { 
                        if (address == IntPtr.Zero) 
                                return null; 
                        else 
                                return Marshal.GetDelegateForFunctionPointer(address, t); 
                } 
 
                ///<summary>    
                ///将表示函数地址的int转换成对应的委托

                ///</summary>    
                public static Delegate GetDelegateFromIntPtr(int address, Type t) 
                { 
                        if (address == 0) 
                                return null; 
                        else 
                                return Marshal.GetDelegateForFunctionPointer(new IntPtr(address), t); 
                } 
 
                delegate short Encrypt(StringBuilder decrypt, StringBuilder encrypt); 
 
                public string ReadDLL() 
                { 
                        int hModule = DLLWrapper.LoadLibrary("CryptoAPI.dll"); 
                        if (hModule == 0) 
                                return "0"; 
                        Encrypt encrypt = (Encrypt)DLLWrapper.GetFunctionAddress(hModule, "Encrypt", typeof(Encrypt)); 
                        if (encrypt == null) 
                        { 
                                DLLWrapper.FreeLibrary(hModule); 
                                return "0"; 
                        } 
                        StringBuilder ss = new StringBuilder(100); 
                        StringBuilder sb = new StringBuilder(100); 
                        sb.Append("aaa"); 
                        encrypt(sb, ss); 
                        DLLWrapper.FreeLibrary(hModule); 
                        return ss.ToString(); 
                } 
        } 
}