RegQueryValueExW

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Runtime.InteropServices;
 
namespace RegView
{
    public partial class Form1 : Form
    {
        [DllImport("advapi32.dll", EntryPoint = "RegOpenKeyW", CharSet = CharSet.Unicode)]
        static extern int RegOpenKey(UIntPtr hKey, string lpSubKey, out UIntPtr phkResult);
        [DllImport("advapi32.dll")]
        static extern int RegCloseKey(UIntPtr hKey);
        [DllImport("advapi32.dll", EntryPoint = "RegQueryValueExW", CharSet = CharSet.Unicode)]
        static extern int RegQueryValueEx(UIntPtr hKey, string lpValueName, int lpReserved, uint lpType, StringBuilder lpData, ref int lpcbData);
 
        public Form1()
        {
            InitializeComponent();
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            
 
            int lDlen;
            UIntPtr hregkey;
            string subkey;
            int retval;
            int lres;
            UIntPtr hKey = (UIntPtr)0x80000001;
 
            subkey = "HKEY_CURRENT_USER\\Environment";
 
            retval = RegOpenKey(hKey, subkey, out hregkey);
         
                lDlen = 1024;
                StringBuilder sData = new StringBuilder(lDlen);
 
                lres = RegQueryValueEx(hregkey, "TMP", 0, 0, sData, ref lDlen);
 
                          retval = RegCloseKey(hregkey);
                textBox1.Text = sData.ToString();
           
        }
        }
    }