Crypto.JS HMAC update

Question

I have some javascript code that I need to convert to C#. I'm struggling with this section. Does C# have a equivalent to this section of code?

function sign(key, content) {
 var hmac = CryptoJS.algo.HMAC.create(CryptoJS.algo.SHA256, CryptoJS.enc.Base64.parse(key));
 hmac.update("".concat(content.timestamp, "|"));
 hmac.update(CryptoJS.enc.Base64.parse(content.nonce));
 hmac.update('|');
 return CryptoJS.enc.Base64.stringify(hmac.finalize());
}

I've started a method in C#, but I don't know how to address the 'update()' method being used above. I believe it refers to progressive hashing, but I'm not certain what that means.

UPDATE* I've created this snippet of code and it works! Is there a more elegant way to do this task?

        using (var hmacsha256 = new HMACSHA256(keyBytes))
        {
            byte[] tmp = new byte[2000];
            hmacsha256.TransformBlock(Encoding.UTF8.GetBytes(s1), 0, s1.Length, tmp, 0);
            hmacsha256.TransformBlock(s2, 0, s2.Length, tmp, s1.Length);
            hmacsha256.TransformBlock(Encoding.UTF8.GetBytes(s3), 0, s3.Length, tmp, s1.Length + s2.Length);
            hmacsha256.TransformBlock(Encoding.UTF8.GetBytes(s4), 0, s4.Length, tmp, s1.Length + s2.Length + s3.Length);
            var final = hmacsha256.TransformFinalBlock(tmp, 0, s1.Length + s2.Length + s3.Length + s4.Length);
            var hash = hmacsha256.ComputeHash(final);

            Console.WriteLine("Expected Result  : 7qJ74WZJFpSzozuXAxQQeTsdEpZDDwBcR4+PZ4glkPY=");
            Console.WriteLine("Actual Result    : " + Convert.ToBase64String(hash));
        }