When using c#, the easiest way to use the PayGate DDMS API is by using the excellent RestSharp package.  You can get this via NuGet by searching for RestSharp.

       private string baseUrl = "https://enterprise.paygate.cloud/ddmsapi";

       private string username = "myUsername";

       private string password = "myPassword";

       private string apiKey = "myApiKey";

           // Request

           // Need to provide Username, Password, ApiKey and the payer's reference

           // Create an anonymous type to hold the data

           var payerRequest = new

           {

               Username = username,

               Password = password,

               ApiKey = apiKey,

               PayerReference = "payerRef"

           };

           // PayGate DDMS API URL for the CreatePayer function

           string paygateApiUrl = $"{baseUrl}/api/Payer/GetPayer";

           // REST call to PayGate DDMS API: CreatePayer

           var client = new RestClient(paygateApiUrl);

           var request = new RestRequest(Method.POST);

           request.AddHeader("cache-control", "no-cache");

           request.AddHeader("content-type", "application/json");

           request.AddJsonBody(payerRequest);

           IRestResponse response = client.Execute(request);

           // Deserialise the response messages from PayGate

           RestSharp.Deserializers.JsonDeserializer deserial = new RestSharp.Deserializers.JsonDeserializer();

           PayerResponse paygateResponse = deserial.Deserialize<PayerResponse>(response);

           // Display the response

           if (paygateResponse.ValidationMessages != null)

               foreach (string message in paygateResponse.ValidationMessages)

                   tbLog.AppendText(message + Environment.NewLine);

           // For demonstration purposes we will use reflection to show the response properties.

           foreach (PropertyInfo propertyInfo in paygateResponse.GetType().GetProperties())

               tbLog.AppendText($"{propertyInfo.Name} - {propertyInfo.GetValue(paygateResponse)}" + Environment.NewLine);

Sample Visual Studio 2017 solution

We have prepared a sample Visual Studio Winforms application to get you started.  This solution contains a definition of the NewAmount class.

The solution can be download from the PayGate portal at this address: https://portal.paygate.cloud/cdn/files/paygate/enterprise/sdk/ddms/RestApi/csharp/2.1.3/DDMSRestClient.zip