How to set int value to PCSTR?

[0x5bfa]

I'm using CryptDecodeObject function in C# using CsWin32. Only initializing PCWSTR with byte*(char*) is allowed. How do I set greater than 255(byte max value)?

private static unsafe CMSG_SIGNER_INFO? GetSignerInfo(void* hMsg, uint index)
{
    nint pbEncodedSigner = nint.Zero;
    uint cbEncodedSigner = 0;
    nint pSignerInfo = nint.Zero;
    uint cbSignerInfo = 0;

    var bResult = PInvoke.CryptMsgGetParam(
        hMsg,
        28, // CMSG_ENCODED_SIGNER
        index,
        null,
        &cbEncodedSigner);

    if (cbEncodedSigner == 0)
    {
        Cleanup(pbEncodedSigner);
        return null;
    }

    pbEncodedSigner = Marshal.AllocHGlobal((int)cbEncodedSigner / Marshal.SizeOf(typeof(byte)));

    bResult = PInvoke.CryptMsgGetParam(
        hMsg,
        28,
        index,
        (void*)pbEncodedSigner,
        ref cbEncodedSigner);

    var error = Marshal.GetLastWin32Error();

    if (cbEncodedSigner == 0)
    {
        Cleanup(pbEncodedSigner);
        return null;
    }

    // HERE!!!
    uint byMsg = 500;
    PCSTR pMsg = new((byte*)&byMsg);

    bResult = PInvoke.CryptDecodeObject(
        CERT_QUERY_ENCODING_TYPE.X509_ASN_ENCODING | CERT_QUERY_ENCODING_TYPE.PKCS_7_ASN_ENCODING,
        pMsg,
        (byte*)pbEncodedSigner,
        cbEncodedSigner,
        0,
        null,
        &cbSignerInfo);

    pSignerInfo = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(CMSG_SIGNER_INFO)));


    return null;

    bool Cleanup(nint pbEncodedSigner)
    {
        if (pbEncodedSigner != nint.Zero)
            Marshal.FreeHGlobal(pbEncodedSigner);

        return false;
    }
}

[AArnott]

You appear to be trying to pass a pointer to the 500 value. That's not what the documentation requires. It wants to see 500 as the value of the pointer itself rather than the value that is pointed to.
I think this will do the trick:

byte* byMsg = (byte*)500;
PCSTR pMsg = new(byMsg);

[0x5bfa]

Oh thank you!!! Really helpful.