C# Signature:

[DllImport("advapi32.dll", SetLastError=true)]
static extern int RegQueryValueEx(
    IntPtr hKey,
    string lpValueName,
    int lpReserved,
    out uint lpType,
    IntPtr lpData,
    ref uint lpcbData);

VB Signature:

Flavor 1: (For strings)
<System.Runtime.InteropServices.DllImport("advapi32.dll", SetLastError:=True)> _
Friend Shared Function RegQueryValueEx( _
    ByVal hKey As IntPtr, _
    ByVal lpValueName As String, _
    ByVal lpReserved As Integer, _
    ByRef lpType As Integer, _
    ByVal lpData As System.Text.StringBuilder, _
    ByRef lpcbData As Integer) As Integer
End Function

Flavor 2: (For binary)
<System.Runtime.InteropServices.DllImport("advapi32.dll", SetLastError:=True)> _
Friend Shared Function RegQueryValueEx( _
    ByVal hKey As IntPtr, _
    ByVal lpValueName As String, _
    ByVal lpReserved As Integer, _
    ByRef lpType As Integer, _
    ByVal lpData As byte(), _
    ByRef lpcbData As Integer) As Integer
End Function

Key Types:

User-Defined Types:

None.

Notes:

Managed APIs won't let you get raw REG_EXPAND_SZ values. You'll be forced to use Win32 APIs for this. Also, since .NET won't give access to the key pointer (hKey), you'll have to browse the registry using pInvoke or use Reflection to query the private member (see sample code for how to).

If you don't need the key type, set it to null

If you don't need data, set both lpData and lpcbData to null

If you only need value size, set lpcbData to null

Tips & Tricks:

None.

Sample Code:

'Allows to read System Environment Path and keeps it unexpanded (in opposition to default .NET behavior)
Dim environmentReg As Microsoft.Win32.RegistryKey = Microsoft.Win32.Registry.LocalMachine.OpenSubKey("SYSTEM\CurrentControlSet\Control\Session Manager\Environment", True)Manager\Environment", True)

'Retrieves the hKey "field"
Dim environmentRegHKey As System.Reflection.FieldInfo = environmentReg.GetType.GetFields(Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)(0)

'Get the instance value back to intPtr
Dim ParentKey As IntPtr = DirectCast(environmentRegHKey.GetValue(environmentReg), IntPtr)

Dim KeyType As Integer 'replace by nothing if you don't need the info
Dim KeyValue As System.Text.StringBuilder
Dim KeyByteValue As Byte()
Dim KeyValueLength As Integer

'First, retrieve buffer size
Dim queryValueReturn As Integer = RegQueryValueEx(ParentKey, "path", Nothing, KeyType, Nothing, KeyValueLength)

'If there is no error
'(if you have an error and you want to know the description, you could call environmentReg's private method GetMessage)
If queryValueReturn = 0 Then
    'Init buffer
    KeyValue = New System.Text.StringBuilder(KeyValueLength)
    ReDim KeyByteValue(KeyValueLength - 1)

    queryValueReturn = RegQueryValueEx(ParentKey, "path", Nothing, KeyType, KeyValue, KeyValueLength)
    queryValueReturn = RegQueryValueEx(ParentKey, "path", Nothing, KeyType, KeyByteValue, KeyValueLength)

    'You should verify the operation succeeded before continuing by validating queryValueReturn
End If

Alternative Managed API:

namespace Microsoft.Win32;

classes Registery, RegistryKey

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