Определение имени текущего пользователя

using System.Management;
using System.Runtime.InteropServices;
using System.Runtime.ConstrainedExecution;
using System.Security;
 
static string GetExplorerUser()
{
    var query = new ObjectQuery("SELECT * FROM Win32_Process WHERE Name='explorer.exe' AND ProcessId=" + GetParentExplorerProcessId());
    var explorerProcesses = new ManagementObjectSearcher(query).Get();
    foreach (ManagementObject mo in explorerProcesses)
    {
        string[] ownerInfo = new string[2];
        mo.InvokeMethod("GetOwner", (object[])ownerInfo);
        return ownerInfo[1] + "\" + ownerInfo[0];
    }
    return "";
}
 
private static uint GetParentExplorerProcessId()
{
    return GetParentExplorerProcessId(Process.GetCurrentProcess().Id);
}
 
private static uint GetParentExplorerProcessId(int processId)
{
    const uint ERROR = 0;
    
    IntPtr hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    if (hSnapshot == IntPtr.Zero) return ERROR;
 
    PROCESSENTRY32 procEntry = new PROCESSENTRY32();
    procEntry.dwSize = (uint)Marshal.SizeOf(typeof(PROCESSENTRY32));
 
    if (Process32First(hSnapshot, ref procEntry) == false) return ERROR;
    
    List<PROCESSENTRY32> ids = new List<PROCESSENTRY32>();
    do
    {
        ids.Add(procEntry);
    }
    while (Process32Next(hSnapshot, ref procEntry));
    CloseHandle(hSnapshot);
    
    uint parentId = ids.Where(pe => pe.th32ProcessID == processId).FirstOrDefault().th32ParentProcessID;
    for(;parentId != 0;)
    {
        string name = ids.Where(pe => pe.th32ProcessID == parentId).FirstOrDefault().szExeFile;
        if ("explorer.exe".Equals(name, StringComparison.OrdinalIgnoreCase)) return parentId;
        
        parentId = ids.Where(pe => pe.th32ProcessID == parentId).FirstOrDefault().th32ParentProcessID;
    }
    
    return ERROR;
}
 
const uint TH32CS_SNAPPROCESS = 2;
 
[StructLayout(LayoutKind.Sequential)]
public struct PROCESSENTRY32
{
    public uint dwSize;
    public uint cntUsage;
    public uint th32ProcessID;
    public IntPtr th32DefaultHeapID;
    public uint th32ModuleID;
    public uint cntThreads;
    public uint th32ParentProcessID;
    public int pcPriClassBase;
    public uint dwFlags;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
    public string szExeFile;
};
 
[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr CreateToolhelp32Snapshot(uint dwFlags, uint th32ProcessID);
 
[DllImport("kernel32.dll")]
static extern bool Process32First(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);
 
[DllImport("kernel32.dll")]
static extern bool Process32Next(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);
 
[DllImport("kernel32.dll", SetLastError=true)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
[SuppressUnmanagedCodeSecurity]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool CloseHandle(IntPtr hObject);