(Mono C#) Adyen HMAC Signature Calculation for Hosted Payment Pages

Demonstrates how to do the HMAC Signature Calculation for a hosted payment page (HPP) in Adyen.

For a C# ASP.NET Razor Pages example showing the HTML Form with HMAC signature code, see Adyen HMAC Signature Calculation in C#

For more information, see https://docs.adyen.com/classic-integration/hosted-payment-pages/hmac-signature-calculation/

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

bool success;

string strHtml = "<table class=\"od\"><tr><th>Description</th><th>Quantity</th><th>Amount</th></tr><tr><td>1 Digital Camera</td><td class=\"r\">1</td><td class=\"r\">100 GBP</td></tr><tr><td class=\"b\">Total</td><td class=\"r\"></td><td class=\"b r\">100.00 GBP</td></tr></table>";

Chilkat.Gzip gzip = new Chilkat.Gzip();
string gzOrderData = gzip.CompressStringENC(strHtml,"utf-8","base64");

Chilkat.Xml xml = new Chilkat.Xml();
xml.Tag = "keyValuePairs";

xml.NewChild2("orderData",gzOrderData);

// required, The payment deadline; the payment needs to occur within the specified time value.
string sessionValidity = "2019-08-11T10:30:00Z";
xml.NewChild2("sessionValidity",sessionValidity);

// optional.  Normally we'll let Adyen automatically know the country based on the IP address.
// By default, the payment methods offered to a shopper are filtered based on the country the shopper's IP address is mapped to. 
// In this way, shoppers are not offered payment methods that are not available in the country they are carrying out the transaction from. 
// This IP-to-country mapping is not 100% accurate, so if you have already established the country of the shopper, you can set it explicitly 
// in the countryCode parameter.
string countryCode = "GB";
xml.NewChild2("countryCode",countryCode);

// optional
string shopperLocale = "en_GB";
// If not specified, the locale preference is set to en_GB   by default.
// When it is not necessary to include the country-specific part, use only the language code.
// For example: it instead of it_IT to set the locale preferences to Italian.
xml.NewChild2("shopperLocale",shopperLocale);

// required, A reference to uniquely identify the payment. This reference is used in all communication with you about the payment status. 
// We recommend using a unique value per payment; however, it is not a requirement. If you need to provide multiple references for a transaction, 
// you can enter them in this field. Separate each reference value with a hyphen character ("-"). This field has a length restriction: 
// you can enter max. 80 characters.
string merchantReference = "paymentTest1234";
xml.NewChild2("merchantReference",merchantReference);

// required, The merchant account identifier you want to process the (transaction) request with.
string merchantAccount = "ChilkatSoftwareIncCOM";
xml.NewChild2("merchantAccount",merchantAccount);

// required.  10000 for $100.00
string paymentAmount = "10000";
xml.NewChild2("paymentAmount",paymentAmount);

// required, The three-character ISO currency code
string currencyCode = "GBP";
xml.NewChild2("currencyCode",currencyCode);

// required.
string skinCode = "S7uWsvfB";
xml.NewChild2("skinCode",skinCode);

// optional, A unique identifier for the shopper, for example, a customer ID.
// We recommend providing this information, as it is used in velocity fraud checks. It is also the key in recurring payments.
// This field is mandatory in recurring payments.  
string shopperReference = "somebody@example.com";
xml.NewChild2("shopperReference",shopperReference);

// optional
string shopperEmail = "somebody@example.com";
xml.NewChild2("shopperEmail",shopperEmail);

// optional, An integer value that adds up to the normal fraud score.
// The value can be either a positive or negative integer.
xml.NewChild2("offset","0");

// Apparently this is a required field.
string shipBeforeDate = "2019-06-04";
xml.NewChild2("shipBeforeDate",shipBeforeDate);

xml.SortByTag(true);

// Encode...
//  "\" (backslash) as "\\"
//  ":" (colon) as "\:"

Chilkat.StringBuilder sbTags = new Chilkat.StringBuilder();
Chilkat.StringBuilder sbValues = new Chilkat.StringBuilder();

Chilkat.StringBuilder sbContent = new Chilkat.StringBuilder();
int n = xml.NumChildren;
int i = 0;
while (i < n) {
    if (i > 0) {
        sbTags.Append(":");
        sbValues.Append(":");
    }

    xml.GetChild2(i);
    sbTags.Append(xml.Tag);

    sbContent.SetString(xml.Content);
    int numReplaced = sbContent.Replace("\\","\\\\");
    numReplaced = sbContent.Replace(":","\\:");
    sbValues.AppendSb(sbContent);
    xml.GetParent2();

    i = i + 1;
}

Chilkat.StringBuilder sbSigningStr = new Chilkat.StringBuilder();
sbSigningStr.AppendSb(sbTags);
sbSigningStr.Append(":");
sbSigningStr.AppendSb(sbValues);

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();
crypt.HashAlgorithm = "sha256";
crypt.MacAlgorithm = "hmac";

string hmacKey = "934D1E806DDD99595EB430076FD7F8E4D12D0A3F51243A4C0C3897703118E739";
crypt.SetMacKeyEncoded(hmacKey,"hex");

crypt.EncodingMode = "base64";
string merchantSig = crypt.HmacStringENC(sbSigningStr.GetAsString());

Debug.WriteLine(merchantSig);