I'm going crazy about this one. Spend whole day and still can't understand what is going on. I'm using AES256CBC encryption both in .Net and JavaScript. For some reason I got different results, despite that I'm using same key an iv. My codes are:

JavaScript:

function convertStringToArrayBuffer(str) {
        var length = str.length;
        var bytes = new Uint8Array(length);
        for(var i = 0; i < length; i++) {
            bytes[i] = str.charCodeAt(i);
        }
        return bytes;
    }

    var keyB64 ="sy/d1Ddy/9K3p8x6pWMq2P8Qw2ftUjkkrAA7xFC7aK8=";
    var viB64 = "t8eI2F+QmlUBWZJVIlTX6Q==";

    var dataToEnc = "Test123!"
    let dataInBytes = convertStringToArrayBuffer(dataToEnc);

    let key = window.atob(keyB64);
    let iv = window.atob(viB64);

    console.log(key);
    console.log(iv);
    window.crypto.subtle.importKey("raw", convertStringToArrayBuffer(key).buffer, {name: "AES-CBC", length: 256}, false, ["encrypt"]).then(function(key){
        console.log(key);
        window.crypto.subtle.encrypt({name: "AES-CBC", iv: convertStringToArrayBuffer(iv).buffer}, key, dataInBytes.buffer).then(function(encrypted){
            console.log(encrypted);
        });
    });

This one produces

.Net:

public static void Test()
        {
            var dataToEnc = "Test123!";
            var keyB64 = "sy/d1Ddy/9K3p8x6pWMq2P8Qw2ftUjkkrAA7xFC7aK8=";
            var viB64 = "t8eI2F+QmlUBWZJVIlTX6Q==";
            var key = Convert.FromBase64String(keyB64);
            var iv = Convert.FromBase64String(viB64);
            var data = Encoding.UTF8.GetBytes(dataToEnc);

            byte[] encrypted = null;
            using (Aes aesAlg = Aes.Create())
            {
                aesAlg.Key = key;
                aesAlg.IV = iv;

                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
                using (MemoryStream msEncrypt = new MemoryStream())
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        {
                            swEncrypt.Write(data);
                        }
                        encrypted = msEncrypt.ToArray();
                    }
                }

            }

        }

This one produces

I belive it is something trivial, yet I can't find this. I appreciate any hint here.