.NET C/C++ P/INVOKE异常

Question

运行这个代码得到这个错误，有没有人能帮我弄清楚这是怎么回事？

​

​

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Runtime.InteropServices;

namespace LSATest
{
class Program
{


    public static List<string> listBox1 = new List<string>(); 
    static void Main(string[] args)
    {
        DateTime systime = new DateTime(1601, 1, 1, 0, 0, 0, 0); //win32 systemdate

        UInt64 count;
        IntPtr luidPtr = IntPtr.Zero;
        LSAClass.LsaEnumerateLogonSessions(out count, out luidPtr);  //gets an array of pointers to LUIDs

        IntPtr iter = luidPtr;      //set the pointer to the start of the array

        for (ulong i = 0; i < count; i++)   //for each pointer in the array
        {
            IntPtr sessionData;

            LSAClass.LsaGetLogonSessionData(iter, out sessionData);

            LSAClass.SECURITY_LOGON_SESSION_DATA data = (LSAClass.SECURITY_LOGON_SESSION_DATA)Marshal.PtrToStructure(sessionData, typeof(LSAClass.SECURITY_LOGON_SESSION_DATA));

            //if we have a valid logon
            if (data.PSiD != IntPtr.Zero)
            {
                //get the security identifier for further use
                System.Security.Principal.SecurityIdentifier sid = new System.Security.Principal.SecurityIdentifier(data.PSiD);

                //extract some useful information from the session data struct
                string username = Marshal.PtrToStringUni(data.Username.buffer).Trim();      //get the account username
                string domain = Marshal.PtrToStringUni(data.LoginDomain.buffer).Trim();    //domain for this account  
                string authpackage = Marshal.PtrToStringUni(data.AuthenticationPackage.buffer).Trim();    //authentication package

                LSAClass.SECURITY_LOGON_TYPE secType = (LSAClass.SECURITY_LOGON_TYPE)data.LogonType;
                DateTime time = systime.AddTicks((long)data.LoginTime);                  //get the datetime the session was logged in

                //do something with the extracted data, ie, add to a display control....
                listBox1.Add("User: " + username + " *** Domain: " + domain + " *** Login Type: (" + data.LogonType + ") " + secType.ToString() + " *** Login Time: " + time.ToLocalTime().ToString());

            }
            iter = (IntPtr)((int)iter + Marshal.SizeOf(typeof(LSAClass.LUID)));  //move the pointer forward
            LSAClass.LsaFreeReturnBuffer(sessionData);   //free the SECURITY_LOGON_SESSION_DATA memory in the struct
        }
        LSAClass.LsaFreeReturnBuffer(luidPtr);   //free the array of LUIDs

    }
}

}

Answer 1

错误是因为sessionData为null。这是因为LsaGetLogonSessionData正在失败。为了进一步诊断这个问题，您需要开始关注API函数的返回值，并在失败的情况下检查错误代码。这就是你的下一步。

顺便说一句，您错误地声明了count变量。在C头文件中，它被声明为ULONG。这是一个无符号的32位整数，在C#中是uint。我没有检查过比这更多的东西了。