How to pass a (byte[] lpData) with integer value to RegSetValueExW P/Invoke

Question

I have this P/Invoke RegSetValueExW that sets the value to the registry key. in C#

[DllImport("coredll.dll", EntryPoint = "RegSetValueExW")]
public static extern int RegSetValueExW(uint hKey, string lpValueName,
            uint lpReserved,
            uint lpType,
            byte[] lpData,
            uint lpcbData);

I'm having a problem with the 4th param byte[] lpdata. I need to pass a DWORD with a value of 5 (int) in it. Everything is OK if I pass a string (REG_SZ), just need to convert using the GetBytes function.

If I call GetBytes("5") it converts it to ascii value of 53 so it writes 53 on the registry value instead of 5

Answer 1

I've got to start by asking why you are using PInvoke here when there is already a method for setting registry values in the Microsoft.Win32.RegistryKey class? Or are you stuck using an old version of the Compact Framework?

Assuming you have a good reason for the PInvoke, the easiest answer is just to overload the PInvoke declaration for integer values. i.e.:

[DllImport("coredll.dll", EntryPoint = "RegSetValueExW")]
public static extern int RegSetValueExW(uint hKey, string lpValueName,
        uint lpReserved,
        uint lpType,
        ref int lpData,
        uint lpcbData);

Answer 2

If you need to pass an integer value you can simply cast it to byte

byte[] lpData = new byte[] { (byte)5 };

Answer 3

Use REG_DWORD instead of REG_SZ and then use BitConverter.GetBytes(Int32) to convert the int to a byte[].

Answer 4

Hi stephen. i am currently using Compact Framework 2.0. So there is no registry classes available

Answer 5

Thanks Guys for the answers. I tried Ste answer and it worked but I guess the proper way to do it is Stephen's answer. Thanks again