Csharp/CSharp Tutorial/Windows/Registry Read

Get int value from Registry

using System;
using Microsoft.Win32;
class MainClass
{
    public static void Main(String[] args)
    {
        int Count = (Int32)Registry.GetValue(
                @"HKEY_CURRENT_USER\Software\CompanyName\SoftwareName",
                "Count", 0); // 0 is the default value
    }
}

Get Registry values with default

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using Microsoft.Win32;
using System.Diagnostics;
public class MainClass{
   public static void Main(){
    RegistryKey regKey = Registry.CurrentUser;
    regKey = regKey.CreateSubKey("Software\\YourCompanyName\\SubDomainName");
    int currFontSize = (int)regKey.GetValue("CurrSize", 12);
    string c = (string)regKey.GetValue("CurrColor", "defaultName");
    
   }
}

Loop through all subkeys contained in the current key

using System;
using Microsoft.Win32;
class MainClass
{
    public static void SearchSubKeys(RegistryKey root, String searchKey)
    {
        
        foreach (string keyname in root.GetSubKeyNames())
        {
            try
            {
                using (RegistryKey key = root.OpenSubKey(keyname))
                {
                    if (keyname == searchKey) 
                        Console.WriteLine("Registry key found : {0} contains {1} values",
                            key.Name, key.ValueCount);
                       
                    SearchSubKeys(key, searchKey);
                }
            }
            catch (System.Security.SecurityException)
            {
            }
        }
    }
    public static void Main(String[] args)
    {
        using (RegistryKey root = Registry.CurrentUser)
        {
            string myKey="Java";
            SearchSubKeys(root, myKey);
        }
    }
}

Loop through the values inside a key and display

using System;
using Microsoft.Win32;
class MainClass
{
    public static void SearchSubKeys(RegistryKey root, String searchKey)
    {
        foreach (string keyname in root.GetSubKeyNames())
        {
            try
            {
                using (RegistryKey key = root.OpenSubKey(keyname))
                {
                    if (keyname == searchKey) {
                        foreach (string valuename in key.GetValueNames())
                        {
                            if (key.GetValue(valuename) is String)
                            {
                                Console.WriteLine("  Value : {0} = {1}",
                                    valuename, key.GetValue(valuename));
                            }
                        }
                    }
                    SearchSubKeys(key, searchKey);
                }
            }
            catch (System.Security.SecurityException)
            {
            }
        }
    }
    public static void Main(String[] args)
    {
        using (RegistryKey root = Registry.CurrentUser)
        {
            string myKey="Java";
            SearchSubKeys(root, myKey);
        }
    }
}

Registry Tree

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using Microsoft.Win32;
  public class RegistryBrowser : System.Windows.Forms.Form
  {
    private System.Windows.Forms.TreeView tvRegistry;
    private System.Windows.Forms.ImageList ilTreeImages;
    public RegistryBrowser()
    {
      InitializeComponent();
      RootNodes();
    }
    private void InitializeComponent()
    {
      this.tvRegistry = new System.Windows.Forms.TreeView();
      this.ilTreeImages = new System.Windows.Forms.ImageList();
      this.SuspendLayout();
      // 
      // tvRegistry
      // 
      this.tvRegistry.Dock = System.Windows.Forms.DockStyle.Fill;
      this.tvRegistry.Name = "tvRegistry";
      this.tvRegistry.Size = new System.Drawing.Size(392, 333);
      this.tvRegistry.TabIndex = 0;
      this.tvRegistry.BeforeExpand += new System.Windows.Forms.TreeViewCancelEventHandler(this.tvRegistry_BeforeExpand);
      // 
      // ilTreeImages
      // 
      this.ilTreeImages.ColorDepth = System.Windows.Forms.ColorDepth.Depth8Bit;
      this.ilTreeImages.TransparentColor = System.Drawing.Color.Transparent;
      // 
      // RegistryBrowser
      // 
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(392, 333);
      this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                      this.tvRegistry});
      this.Name = "RegistryBrowser";
      this.Text = "Registry Browser";
      this.ResumeLayout(false);
    }
    static void Main() 
    {
      Application.Run(new RegistryBrowser());
    }
    private void tvRegistry_BeforeExpand(object sender, System.Windows.Forms.TreeViewCancelEventArgs e)
    {
      tvRegistry.BeginUpdate();
      foreach (TreeNode tn in e.Node.Nodes)
      {
        AddBranch(tn);
      }
      tvRegistry.EndUpdate();
    }
    public void AddBranch(TreeNode tn)
    {
      tn.Nodes.Clear();
      string strRegistryPath = tn.FullPath;
      RegistryKey regBranch = null;
      if (strRegistryPath.StartsWith("HKEY_CLASSES_ROOT"))
        regBranch = Registry.ClassesRoot;
      else if (strRegistryPath.StartsWith("HKEY_CURRENT_USER"))
        regBranch = Registry.CurrentUser;
      else if (strRegistryPath.StartsWith("HKEY_LOCAL_MACHINE"))
        regBranch = Registry.LocalMachine;
        else if (strRegistryPath.StartsWith("HKEY_USERS"))
        regBranch = Registry.Users;
      RegistryKey regSubKey = null;
      try
      {
        if (null != tn.Parent)
        {
          // we need the path minus the top level tree
          int nPosPathSeparator = strRegistryPath.IndexOf(this.tvRegistry.PathSeparator);
          string strSubkey = strRegistryPath.Substring(nPosPathSeparator+1);
          regSubKey = regBranch.OpenSubKey(strSubkey);
        }
        else
          regSubKey = regBranch;
      }
      catch
      {
        return;
      }
      string[] astrSubkeyNames = regSubKey.GetSubKeyNames();
      for (int i=0; i < astrSubkeyNames.Length; i++)
      {
        TreeNode tnBranch = new TreeNode(astrSubkeyNames[i],0,1);
        tn.Nodes.Add(tnBranch);
      }
    }
    public void RootNodes()
    {
      tvRegistry.BeginUpdate();
      TreeNode tnHKCR = new TreeNode("HKEY_CLASSES_ROOT",0,1);
      tvRegistry.Nodes.Add(tnHKCR);
      AddBranch(tnHKCR);
      TreeNode tnHKCU = new TreeNode("HKEY_CURRENT_USER",0,1);
      tvRegistry.Nodes.Add(tnHKCU);
      AddBranch(tnHKCU);
      TreeNode tnHKLM = new TreeNode("HKEY_LOCAL_MACHINE",0,1);
      tvRegistry.Nodes.Add(tnHKLM);
      AddBranch(tnHKLM);
      TreeNode tnHKU = new TreeNode("HKEY_USERS",0,1);
      tvRegistry.Nodes.Add(tnHKU);
      AddBranch(tnHKU);
      tvRegistry.SelectedNode = tnHKLM;
      tvRegistry.EndUpdate();
    }
  }

Registry Tree With Class

using System;
using System.Drawing;
using System.IO;
using System.Windows.Forms;
using Microsoft.Win32;
  public class RegistryTreeClass: TreeView
  {
    public RegistryTreeClass()
    {
      ImageList = new ImageList();
      ImageList.Images.Add(new Bitmap(GetType(), "CLOSED.BMP"));
      ImageList.Images.Add(new Bitmap(GetType(), "OPEN.BMP"));
      RootNodes();
    }
    protected override void OnBeforeExpand(TreeViewCancelEventArgs e)
    {
      base.OnBeforeExpand(e);
      BeginUpdate();
      foreach (TreeNode tn in e.Node.Nodes)
      {
        AddBranch(tn);
      }
      EndUpdate();
    }
    
    public void RootNodes()
    {
      BeginUpdate();
      TreeNode tnHKCR = new TreeNode("HKEY_CLASSES_ROOT",0,1);
      Nodes.Add(tnHKCR);
      AddBranch(tnHKCR);
      TreeNode tnHKCU = new TreeNode("HKEY_CURRENT_USER",0,1);
      Nodes.Add(tnHKCU);
      AddBranch(tnHKCU);
      TreeNode tnHKLM = new TreeNode("HKEY_LOCAL_MACHINE",0,1);
      Nodes.Add(tnHKLM);
      AddBranch(tnHKLM);
      TreeNode tnHKU = new TreeNode("HKEY_USERS",0,1);
      Nodes.Add(tnHKU);
      AddBranch(tnHKU);
      SelectedNode = tnHKLM;
      EndUpdate();
    }
    public void AddBranch(TreeNode tn)
    {
      if (tn.Nodes.Count > 0) return;
      string strRegistryPath = tn.FullPath;
      RegistryKey regBranch = null;
      if (strRegistryPath.StartsWith("HKEY_CLASSES_ROOT"))
        regBranch = Registry.ClassesRoot;
      else if (strRegistryPath.StartsWith("HKEY_CURRENT_USER"))
        regBranch = Registry.CurrentUser;
      else if (strRegistryPath.StartsWith("HKEY_LOCAL_MACHINE"))
        regBranch = Registry.LocalMachine;
      else if (strRegistryPath.StartsWith("HKEY_USERS"))
        regBranch = Registry.Users;
      RegistryKey regSubKey = null;
      try
      {
        if (null != tn.Parent)
        {
          // We need the path minus the top level tree.
          int nPosPathSeparator = strRegistryPath.IndexOf(this.PathSeparator);
          string strSubkey = strRegistryPath.Substring(nPosPathSeparator+1);
          regSubKey = regBranch.OpenSubKey(strSubkey);
        }
        else
          regSubKey = regBranch;
      }
      catch
      {
        return;
      }
      string[] astrSubkeyNames = regSubKey.GetSubKeyNames();
      for (int i=0; i < astrSubkeyNames.Length; i++)
      {
        TreeNode tnBranch = new TreeNode(astrSubkeyNames[i],0,1);
        tn.Nodes.Add(tnBranch);
      }
    }
  }
  public class MainForm : System.Windows.Forms.Form
  {
    private RegistryTreeClass rtvRegistry;
    public MainForm()
    {
      InitializeComponent();
      this.rtvRegistry = new RegistryTreeClass();
      this.SuspendLayout();
      this.rtvRegistry.Dock = System.Windows.Forms.DockStyle.Fill;
      this.rtvRegistry.ImageIndex = -1;
      this.rtvRegistry.Name = "rtvRegistry";
      this.rtvRegistry.SelectedImageIndex = -1;
      this.rtvRegistry.Size = new System.Drawing.Size(292, 273);
      this.rtvRegistry.TabIndex = 0;
      this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                      this.rtvRegistry});
      this.ResumeLayout(false);
    }
    private void InitializeComponent()
    {
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(292, 273);
      this.Name = "MainForm";
      this.Text = "Registry with class";
      this.Load += new System.EventHandler(this.Form1_Load);
    }
    static void Main() 
    {
      Application.Run(new MainForm());
    }
    private void Form1_Load(object sender, System.EventArgs e)
    {
    
    }
  }