RegistryKey.OpenSubKey Method
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Retrieves the specified subkey.
Overloads
OpenSubKey(String, Boolean) |
Retrieves a specified subkey, and specifies whether write access is to be applied to the key. |
OpenSubKey(String, RegistryKeyPermissionCheck, RegistryRights) |
Retrieves the specified subkey for read or read/write access, requesting the specified access rights. |
OpenSubKey(String, RegistryRights) |
Retrieves a subkey with the specified name and access rights. Available starting with .NET Framework 4.6. |
OpenSubKey(String) |
Retrieves a subkey as read-only. |
OpenSubKey(String, RegistryKeyPermissionCheck) |
Retrieves the specified subkey for read or read/write access. |
OpenSubKey(String, Boolean)
- Source:
- RegistryKey.cs
Retrieves a specified subkey, and specifies whether write access is to be applied to the key.
public:
Microsoft::Win32::RegistryKey ^ OpenSubKey(System::String ^ name, bool writable);
public Microsoft.Win32.RegistryKey? OpenSubKey (string name, bool writable);
public Microsoft.Win32.RegistryKey OpenSubKey (string name, bool writable);
member this.OpenSubKey : string * bool -> Microsoft.Win32.RegistryKey
Public Function OpenSubKey (name As String, writable As Boolean) As RegistryKey
Parameters
- name
- String
Name or path of the subkey to open.
- writable
- Boolean
Set to true
if you need write access to the key.
Returns
The subkey requested, or null
if the operation failed.
Exceptions
name
is null
.
The RegistryKey is closed (closed keys cannot be accessed).
The user does not have the permissions required to access the registry key in the specified mode.
Examples
The following code example creates a test key and uses the OpenSubKey method to open it, demonstrating both overloads of the method.
#using <Microsoft.VisualBasic.dll>
using namespace System;
using namespace Microsoft::Win32;
using namespace Microsoft::VisualBasic;
int main()
{
// Delete and recreate the test key.
Registry::CurrentUser->DeleteSubKey( L"RegistryOpenSubKeyExample", false );
RegistryKey ^ rk = Registry::CurrentUser->CreateSubKey( L"RegistryOpenSubKeyExample" );
rk->Close();
// 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( L"RegistryOpenSubKeyExample" );
Console::WriteLine( L"Test key: {0}", rkTest );
rkTest->Close();
rkCurrentUser->Close();
// Obtain the test key in one step, using the CurrentUser registry
// root.
rkTest = Registry::CurrentUser->OpenSubKey( L"RegistryOpenSubKeyExample" );
Console::WriteLine( L"Test key: {0}", rkTest );
rkTest->Close();
// Open the test key in read/write mode.
rkTest = Registry::CurrentUser->OpenSubKey( L"RegistryOpenSubKeyExample", true );
rkTest->SetValue( L"TestName", L"TestValue" );
Console::WriteLine( L"Test value for TestName: {0}", rkTest->GetValue( L"TestName" ) );
rkTest->Close();
return 0;
} //Main
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");
rk.Close();
// 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);
rkTest.Close();
rkCurrentUser.Close();
// Obtain the test key in one step, using the CurrentUser registry
// root.
rkTest = Registry.CurrentUser.OpenSubKey("RegistryOpenSubKeyExample");
Console.WriteLine("Test key: {0}", rkTest);
rkTest.Close();
// 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"));
rkTest.Close();
} //Main
} //Example
Imports Microsoft.Win32
Public Class Example
Public Shared Sub Main()
' Delete and recreate the test key.
Registry.CurrentUser.DeleteSubKey("RegistryOpenSubKeyExample", False)
Dim rk As RegistryKey = Registry.CurrentUser.CreateSubKey("RegistryOpenSubKeyExample")
rk.Close
' Obtain an instance of RegistryKey for the CurrentUser registry
' root.
Dim rkCurrentUser As RegistryKey = Registry.CurrentUser
' Obtain the test key (read-only) and display it.
Dim rkTest As RegistryKey = rkCurrentUser.OpenSubKey("RegistryOpenSubKeyExample")
Console.WriteLine("Test key: {0}", rkTest)
rkTest.Close
rkCurrentUser.Close
' Obtain the test key in one step, using the CurrentUser registry
' root.
rkTest = Registry.CurrentUser.OpenSubKey("RegistryOpenSubKeyExample")
Console.WriteLine("Test key: {0}", rkTest)
rkTest.Close
' Obtain 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"))
rkTest.Close
End Sub
End Class
Remarks
If the requested key does not exist, this method returns null
instead of throwing an exception.
If writable
is true
, the key will be opened for reading and writing, otherwise, the key will be opened as read-only.
In order to use the OpenSubKey method, you must have an instance of the RegistryKey method. To get an instance of RegistryKey, use one of the static members of the Registry class.
See also
- CreateSubKey(String)
- DeleteSubKey(String)
- DeleteSubKeyTree(String)
- GetSubKeyNames()
- OpenRemoteBaseKey(RegistryHive, String)
- SubKeyCount
- Registry
Applies to
OpenSubKey(String, RegistryKeyPermissionCheck, RegistryRights)
- Source:
- RegistryKey.cs
Retrieves the specified subkey for read or read/write access, requesting the specified access rights.
public:
Microsoft::Win32::RegistryKey ^ OpenSubKey(System::String ^ name, Microsoft::Win32::RegistryKeyPermissionCheck permissionCheck, System::Security::AccessControl::RegistryRights rights);
public Microsoft.Win32.RegistryKey? OpenSubKey (string name, Microsoft.Win32.RegistryKeyPermissionCheck permissionCheck, System.Security.AccessControl.RegistryRights rights);
[System.Runtime.InteropServices.ComVisible(false)]
public Microsoft.Win32.RegistryKey OpenSubKey (string name, Microsoft.Win32.RegistryKeyPermissionCheck permissionCheck, System.Security.AccessControl.RegistryRights rights);
public Microsoft.Win32.RegistryKey OpenSubKey (string name, Microsoft.Win32.RegistryKeyPermissionCheck permissionCheck, System.Security.AccessControl.RegistryRights rights);
member this.OpenSubKey : string * Microsoft.Win32.RegistryKeyPermissionCheck * System.Security.AccessControl.RegistryRights -> Microsoft.Win32.RegistryKey
[<System.Runtime.InteropServices.ComVisible(false)>]
member this.OpenSubKey : string * Microsoft.Win32.RegistryKeyPermissionCheck * System.Security.AccessControl.RegistryRights -> Microsoft.Win32.RegistryKey
Public Function OpenSubKey (name As String, permissionCheck As RegistryKeyPermissionCheck, rights As RegistryRights) As RegistryKey
Parameters
- name
- String
The name or path of the subkey to create or open.
- permissionCheck
- RegistryKeyPermissionCheck
One of the enumeration values that specifies whether the key is opened for read or read/write access.
- rights
- RegistryRights
A bitwise combination of enumeration values that specifies the desired security access.
Returns
The subkey requested, or null
if the operation failed.
- Attributes
Exceptions
name
is null
permissionCheck
contains an invalid value.
The RegistryKey is closed (closed keys cannot be accessed).
rights
includes invalid registry rights values.
-or-
The user does not have the requested permissions.
Remarks
Rather than throwing an exception, this method returns null
if the requested key does not exist.
If permissionCheck
is RegistryKeyPermissionCheck.ReadWriteSubTree, the key is opened for reading and writing; if permissionCheck
is RegistryKeyPermissionCheck.ReadSubTree or RegistryKeyPermissionCheck.Default, the key is opened for reading unless the parent key was opened with RegistryKeyPermissionCheck.ReadWriteSubTree.
The access specified for permissionCheck
takes precedence over the access specified for rights
. For example, if you specify RegistryKeyPermissionCheck.ReadSubTree for permissionCheck
and RegistryRights.WriteKey for rights
, an attempt to write to the subkey throws an exception.
In order to use the OpenSubKey method, you must have an instance of the RegistryKey class. To get an instance of RegistryKey, use one of the static members of the Registry class.
See also
- CreateSubKey(String)
- DeleteSubKey(String)
- DeleteSubKeyTree(String)
- GetSubKeyNames()
- OpenRemoteBaseKey(RegistryHive, String)
- SubKeyCount
- Registry
Applies to
OpenSubKey(String, RegistryRights)
- Source:
- RegistryKey.cs
Retrieves a subkey with the specified name and access rights. Available starting with .NET Framework 4.6.
public:
Microsoft::Win32::RegistryKey ^ OpenSubKey(System::String ^ name, System::Security::AccessControl::RegistryRights rights);
public Microsoft.Win32.RegistryKey? OpenSubKey (string name, System.Security.AccessControl.RegistryRights rights);
public Microsoft.Win32.RegistryKey OpenSubKey (string name, System.Security.AccessControl.RegistryRights rights);
[System.Runtime.InteropServices.ComVisible(false)]
public Microsoft.Win32.RegistryKey OpenSubKey (string name, System.Security.AccessControl.RegistryRights rights);
member this.OpenSubKey : string * System.Security.AccessControl.RegistryRights -> Microsoft.Win32.RegistryKey
[<System.Runtime.InteropServices.ComVisible(false)>]
member this.OpenSubKey : string * System.Security.AccessControl.RegistryRights -> Microsoft.Win32.RegistryKey
Public Function OpenSubKey (name As String, rights As RegistryRights) As RegistryKey
Parameters
- name
- String
The name or path of the subkey to create or open.
- rights
- RegistryRights
The rights for the registry key.
Returns
The subkey requested, or null
if the operation failed.
- Attributes
Exceptions
name
is null
.
The RegistryKey is closed (closed keys cannot be accessed).
The user does not have the permissions required to access the registry key in the specified mode.
Remarks
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.
Applies to
OpenSubKey(String)
- Source:
- RegistryKey.cs
Retrieves a subkey as read-only.
public:
Microsoft::Win32::RegistryKey ^ OpenSubKey(System::String ^ name);
public Microsoft.Win32.RegistryKey? OpenSubKey (string name);
public Microsoft.Win32.RegistryKey OpenSubKey (string name);
member this.OpenSubKey : string -> Microsoft.Win32.RegistryKey
Public Function OpenSubKey (name As String) As RegistryKey
Parameters
- name
- String
The name or path of the subkey to open as read-only.
Returns
The subkey requested, or null
if the operation failed.
Exceptions
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.
Examples
The following code example creates a test key and uses the OpenSubKey method to open it, demonstrating both overloads of the method.
#using <Microsoft.VisualBasic.dll>
using namespace System;
using namespace Microsoft::Win32;
using namespace Microsoft::VisualBasic;
int main()
{
// Delete and recreate the test key.
Registry::CurrentUser->DeleteSubKey( L"RegistryOpenSubKeyExample", false );
RegistryKey ^ rk = Registry::CurrentUser->CreateSubKey( L"RegistryOpenSubKeyExample" );
rk->Close();
// 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( L"RegistryOpenSubKeyExample" );
Console::WriteLine( L"Test key: {0}", rkTest );
rkTest->Close();
rkCurrentUser->Close();
// Obtain the test key in one step, using the CurrentUser registry
// root.
rkTest = Registry::CurrentUser->OpenSubKey( L"RegistryOpenSubKeyExample" );
Console::WriteLine( L"Test key: {0}", rkTest );
rkTest->Close();
// Open the test key in read/write mode.
rkTest = Registry::CurrentUser->OpenSubKey( L"RegistryOpenSubKeyExample", true );
rkTest->SetValue( L"TestName", L"TestValue" );
Console::WriteLine( L"Test value for TestName: {0}", rkTest->GetValue( L"TestName" ) );
rkTest->Close();
return 0;
} //Main
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");
rk.Close();
// 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);
rkTest.Close();
rkCurrentUser.Close();
// Obtain the test key in one step, using the CurrentUser registry
// root.
rkTest = Registry.CurrentUser.OpenSubKey("RegistryOpenSubKeyExample");
Console.WriteLine("Test key: {0}", rkTest);
rkTest.Close();
// 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"));
rkTest.Close();
} //Main
} //Example
Imports Microsoft.Win32
Public Class Example
Public Shared Sub Main()
' Delete and recreate the test key.
Registry.CurrentUser.DeleteSubKey("RegistryOpenSubKeyExample", False)
Dim rk As RegistryKey = Registry.CurrentUser.CreateSubKey("RegistryOpenSubKeyExample")
rk.Close
' Obtain an instance of RegistryKey for the CurrentUser registry
' root.
Dim rkCurrentUser As RegistryKey = Registry.CurrentUser
' Obtain the test key (read-only) and display it.
Dim rkTest As RegistryKey = rkCurrentUser.OpenSubKey("RegistryOpenSubKeyExample")
Console.WriteLine("Test key: {0}", rkTest)
rkTest.Close
rkCurrentUser.Close
' Obtain the test key in one step, using the CurrentUser registry
' root.
rkTest = Registry.CurrentUser.OpenSubKey("RegistryOpenSubKeyExample")
Console.WriteLine("Test key: {0}", rkTest)
rkTest.Close
' Obtain 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"))
rkTest.Close
End Sub
End Class
Remarks
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.
See also
- CreateSubKey(String)
- DeleteSubKey(String)
- DeleteSubKeyTree(String)
- GetSubKeyNames()
- OpenRemoteBaseKey(RegistryHive, String)
- SubKeyCount
- Registry
Applies to
OpenSubKey(String, RegistryKeyPermissionCheck)
- Source:
- RegistryKey.cs
Retrieves the specified subkey for read or read/write access.
public:
Microsoft::Win32::RegistryKey ^ OpenSubKey(System::String ^ name, Microsoft::Win32::RegistryKeyPermissionCheck permissionCheck);
public Microsoft.Win32.RegistryKey? OpenSubKey (string name, Microsoft.Win32.RegistryKeyPermissionCheck permissionCheck);
[System.Runtime.InteropServices.ComVisible(false)]
public Microsoft.Win32.RegistryKey OpenSubKey (string name, Microsoft.Win32.RegistryKeyPermissionCheck permissionCheck);
public Microsoft.Win32.RegistryKey OpenSubKey (string name, Microsoft.Win32.RegistryKeyPermissionCheck permissionCheck);
member this.OpenSubKey : string * Microsoft.Win32.RegistryKeyPermissionCheck -> Microsoft.Win32.RegistryKey
[<System.Runtime.InteropServices.ComVisible(false)>]
member this.OpenSubKey : string * Microsoft.Win32.RegistryKeyPermissionCheck -> Microsoft.Win32.RegistryKey
Public Function OpenSubKey (name As String, permissionCheck As RegistryKeyPermissionCheck) As RegistryKey
Parameters
- name
- String
The name or path of the subkey to create or open.
- permissionCheck
- RegistryKeyPermissionCheck
One of the enumeration values that specifies whether the key is opened for read or read/write access.
Returns
The subkey requested, or null
if the operation failed.
- Attributes
Exceptions
name
is null
permissionCheck
contains an invalid value.
The RegistryKey is closed (closed keys cannot be accessed).
The user does not have the permissions required to read the registry key.
Examples
The following code example creates a subkey containing 100 key/value pairs and closes it. The example opens the subkey with Default, records the time it takes to read all the values, and closes the subkey. The example opens the subkey with ReadSubTree and records the time it takes to read all the values. Finally, the example computes and displays the percentage improvement.
using System;
using Microsoft.Win32;
using System.Diagnostics;
public class Example
{
public static void Main()
{
const int LIMIT = 100;
RegistryKey cu = Registry.CurrentUser;
const string testKey = "RegistryKeyPermissionCheckExample";
Console.WriteLine("Generating {0} key/value pairs.", LIMIT);
RegistryKey rk = cu.CreateSubKey(testKey);
for (int i = 0; i < LIMIT; i++)
{
rk.SetValue("Key" + i, i);
}
rk.Close();
Stopwatch s = new Stopwatch();
// On the default setting, security is checked every time
// a key/value pair is read.
rk = cu.OpenSubKey(testKey, RegistryKeyPermissionCheck.Default);
s.Start();
for (int i = 0; i < LIMIT; i++)
{
rk.GetValue("Key" + i, i);
}
s.Stop();
rk.Close();
long delta1 = s.ElapsedTicks;
s.Reset();
// When the key is opened with ReadSubTree, security is
// not checked when the values are read.
rk = cu.OpenSubKey(testKey, RegistryKeyPermissionCheck.ReadSubTree);
s.Start();
for (int i = 0; i < LIMIT; i++)
{
rk.GetValue("Key" + i, i);
}
s.Stop();
rk.Close();
long delta2 = s.ElapsedTicks;
double faster = (double) (delta1 - delta2) / (double) delta1;
Console.WriteLine("ReadSubTree is {0}% faster for {1} values.",
(faster * 100).ToString("0.0"), LIMIT);
cu.DeleteSubKey(testKey);
}
}
/* This code example produces output similar to the following:
Generating 100 key/value pairs.
ReadSubTree is 23.4% faster for 100 values.
*/
Imports Microsoft.Win32
Imports System.Diagnostics
Public Class Example
Public Shared Sub Main()
Const LIMIT As Integer = 100
Dim cu As RegistryKey = Registry.CurrentUser
Const testKey As String = "RegistryKeyPermissionCheckExample"
Console.WriteLine("Generating {0} key/value pairs.", LIMIT)
Dim rk As RegistryKey = cu.CreateSubKey(testKey)
For i As Integer = 0 To LIMIT
rk.SetValue("Key" & i, i)
Next i
rk.Close()
Dim s As New Stopwatch()
' On the default setting, security is checked every time
' a key/value pair is read.
rk = cu.OpenSubKey(testKey, _
RegistryKeyPermissionCheck.Default)
s.Start()
For i As Integer = 0 To LIMIT
rk.GetValue("Key" & i, i)
Next i
s.Stop()
rk.Close()
Dim delta1 As Long = s.ElapsedTicks
s.Reset()
' When the key is opened with ReadSubTree, security is
' not checked when the values are read.
rk = cu.OpenSubKey(testKey, _
RegistryKeyPermissionCheck.ReadSubTree)
s.Start()
For i As Integer = 0 To LIMIT
rk.GetValue("Key" & i, i)
Next i
s.Stop()
rk.Close()
Dim delta2 As Long = s.ElapsedTicks
Dim faster As Double = _
CDbl(delta1 - delta2) * 100.0 / CDbl(delta1)
Console.WriteLine("ReadSubTree is {0}% faster for {1} values.", _
faster.ToString("0.0"), LIMIT)
cu.DeleteSubKey(testKey)
End Sub
End Class
' This code example produces output similar to the following:
'
'Generating 100 key/value pairs.
'ReadSubTree is 23.4% faster for 100 values.
'
Remarks
Rather than throwing an exception, this method returns null
if the requested key does not exist.
If permissionCheck
is RegistryKeyPermissionCheck.ReadWriteSubTree, the key is opened for reading and writing; if permissionCheck
is RegistryKeyPermissionCheck.ReadSubTree or RegistryKeyPermissionCheck.Default, the key is opened for reading unless the parent key was opened with RegistryKeyPermissionCheck.ReadWriteSubTree.
In order to use the OpenSubKey method, you must have an instance of the RegistryKey class. To get an instance of RegistryKey, use one of the static members of the Registry class.
See also
- CreateSubKey(String)
- DeleteSubKey(String)
- DeleteSubKeyTree(String)
- GetSubKeyNames()
- OpenRemoteBaseKey(RegistryHive, String)
- SubKeyCount
- Registry
Applies to
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