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RegistryKey.OpenSubKey Method (String)

Retrieves a subkey as read-only.

Namespace:  Microsoft.Win32
Assembly:  mscorlib (in mscorlib.dll)

public RegistryKey OpenSubKey(
	string name


Type: System.String
The name or path of the subkey to open as read-only.

Return Value

Type: Microsoft.Win32.RegistryKey
The subkey requested, or null if the operation failed.


name is null


The RegistryKey is closed (closed keys cannot be accessed).


The user does not have the permissions required to read the registry key.

You must open a key before it can be manipulated with other methods and properties. To modify a key, you must open it with an overload of the OpenSubKey method that allows you to specify write access, such as the OpenSubKey(String, RegistryKeyPermissionCheck) overload or the OpenSubKey(String, Boolean) overload.

If the specified subkey cannot be found, then null is returned.

In order to use the OpenSubKey method, you must have an instance of RegistryKey. To get an instance of RegistryKey, use the one of the static members of the Registry class.

The following code example creates a test key and uses the OpenSubKey method to open it, demonstrating both overloads of the method.

using System;
using Microsoft.Win32;
using Microsoft.VisualBasic;

public class Example
    public static void Main()
        // Delete and recreate the test key.
        Registry.CurrentUser.DeleteSubKey("RegistryOpenSubKeyExample", false);
        RegistryKey rk = Registry.CurrentUser.CreateSubKey("RegistryOpenSubKeyExample");

        // Obtain an instance of RegistryKey for the CurrentUser registry 
        // root. 
        RegistryKey rkCurrentUser = Registry.CurrentUser;

        // Obtain the test key (read-only) and display it.
        RegistryKey rkTest = rkCurrentUser.OpenSubKey("RegistryOpenSubKeyExample");
        Console.WriteLine("Test key: {0}", rkTest);

        // Obtain the test key in one step, using the CurrentUser registry 
        // root.
        rkTest = Registry.CurrentUser.OpenSubKey("RegistryOpenSubKeyExample");
        Console.WriteLine("Test key: {0}", rkTest);

        // Open the test key in read/write mode.
        rkTest = Registry.CurrentUser.OpenSubKey("RegistryOpenSubKeyExample", true);
        rkTest.SetValue("TestName", "TestValue");
        Console.WriteLine("Test value for TestName: {0}", rkTest.GetValue("TestName"));
    } //Main
} //Example

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.