C # Confirm Signature

I have the following code to sign my data before sending (http):

    internal static byte[] Encode(byte[] arMessage, string signerCert, string signerPassword)
            {
                X509Certificate2 cert = new X509Certificate2(signerCert, signerPassword);
                //debug data
                var msg = System.Text.ASCIIEncoding.ASCII.GetString(arMessage);
                //--
                ContentInfo contentInfo = new ContentInfo(arMessage);

                SignedCms signedCms = new SignedCms(contentInfo, true); // <- true detaches the signature
                CmsSigner cmsSigner = new CmsSigner(cert);

                signedCms.ComputeSignature(cmsSigner);
                byte[] signature = signedCms.Encode();

                return signature;
            }

I see a signature after following these steps:

    string sig = Convert.ToBase64String(bSignature) + MESSAGE_SEPARATOR;
    //this will be included in the message:
    bSignature = System.Text.ASCIIEncoding.ASCII.GetBytes(sig);

    //debug data, see the signature:
    string deb8 = System.Text.ASCIIEncoding.ASCII.GetString(bSignature);
    //--

For instance:

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

This is what I received in the received message. So, the question is : how to check the signature of the received message at the recipient (is there a .cer file)? thanks in advance

Edit 1:

I tried to follow the logic of Daniel Hilgart, but that didn't work. Several times I met the exception "ASN Bad tag value". To make it easier, I hard-coded the message used to generate the signature. So, I have 2 things on the receiver: the original message and the signature generated for it:

    //Signature from the message  (string in ASCII)
    var signatureKey = GetSignatureFromSignatureMessage(signatureMessage, boundary);
    //Original sent message (the arMessage itself used in Encode method above, converted to string from byte) 
    var messageOriginal =
        "Content-Type: application/EDIFACT\r\nContent-Transfer-Encoding: binary\r\n\r\nSome short text.\r\nVery short.";

I need to check if the signature matches this post. So I am trying to do something like this:

//contentInfo from the original message.
ContentInfo contentInfo = new ContentInfo(System.Text.ASCIIEncoding.ASCII.GetBytes(messageOriginal));

//SingedCms from the contentInfo above
SignedCms signedCms = new SignedCms(contentInfo, true);

//Here, I believe, I am attaching the signature I have to the Cms    
 signedCms.Decode(System.Text.ASCIIEncoding.ASCII.GetBytes(signatureKey));

//checking?
signedCms.CheckSignature(true);

.

?

2: : . , : Base64 → Base64String → ASCII → ASCII → Send_message ASCII, : ASCII String → . base64, .

    //Signature from the message (ASCII String)
    var signatureKey = GetSignatureFromSignatureMessage(signatureMessage, boundary);

    //Original Byte Array (Base64)
    var sigKeyBase = Convert.FromBase64String(signatureKey);

   //Original sent message
    var messageOriginal =
        "Content-Type: application/EDIFACT\r\nContent-Transfer-Encoding: binary\r\n\r\nSome short text.\r\nVery short.";

    var messageOriginalByteASCII = System.Text.ASCIIEncoding.ASCII.GetBytes(messageOriginal);


    ContentInfo contentInfo = new ContentInfo(messageOriginalByteASCII);
    SignedCms signedCms = new SignedCms(contentInfo, true);
    signedCms.Decode(sigKeyBase);

    signedCms.CheckSignature(true);

. ChekSignature true false. .: (