Different results between System.Security.SignedCms and BouncyCastle CmsSignedDataGenerator

Question

I need make pksc#7 signature. It's my working (time to time) code with SignedCms:

public static string SignSignedCms(string data)
{
    byte[] bData = Encoding.UTF8.GetBytes(data);

    X509Certificate2 certificate = new X509Certificate2();

    certificate.Import(@"D:\...file.pfx", "pwd", X509KeyStorageFlags.DefaultKeySet);

    ContentInfo content = new ContentInfo(bData);
    SignedCms signedCms = new SignedCms(content);

    CmsSigner signer = new CmsSigner(certificate);
    signer.DigestAlgorithm = new Oid("SHA256");

    signedCms.ComputeSignature(signer, true);
    return Convert.ToBase64String(signedCms.Encode()).TrimEnd('=').Replace('+', '-').Replace('/', '_');
}

if data="asdfghjkl" result is: MIIFbAYJKoZIhvcNAQcCoIIFXTCCBVkCAQExDzANBglghkg...IRmmg0beHTRwKd - 1857 sybols

In this case I have same result every time.

Now I need different way for making same thing (why? - it's other question)

I found BouncyCastle CmsSignedDataGenerator and I have this:

public static string SignBouncyCastle(string data)
{
    byte[] bData = Encoding.UTF8.GetBytes(data);

    X509Certificate2 certificate = new X509Certificate2();

    certificate.Import(@"D:\...file.pfx", "pwd", 509KeyStorageFlags.Exportable);

    AsymmetricKeyParameter key = DotNetUtilities.GetKeyPair(certificate.PrivateKey).Private;

    CmsSignedDataGenerator gen = new CmsSignedDataGenerator();

    gen.AddSigner(key, DotNetUtilities.FromX509Certificate(certificate), CmsSignedGenerator.DigestSha256);

    CmsSignedData cmsSignedData = gen.Generate(new CmsProcessableByteArray(bData));

    return Convert.ToBase64String(cmsSignedData.GetEncoded()).TrimEnd('=').Replace('+', '-').Replace('/', '_');
}

In this case (data="asdfghjkl") I always have different results, something like this: MIAGCSqGSIb3DQEHAqCAMIACAQExDzANB...egV70FgAAAAAAAA - 811 symbols!

Both methods should make "detached pkcs7-signature message", but BouncyCastle makes something different.

I'm sure that SignedCms makes right signature, but I can't use it.

What should I change in my second method to have the same result like in SignedCms?

SignedCms - https://msdn.microsoft.com/en-us/library/8412wc31%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396

CMSSignedDataGenerator - https://www.bouncycastle.org/docs/pkixdocs1.5on/org/bouncycastle/cms/CMSSignedDataGenerator.html

I don't see difference!