api.cs

var os = new OAuthSettings(
     "dsserver.yqBdWzA3x4toe123prtSPYZZqTljS8JY",
     "ggWxH3sWaQH123anqM6Vsazyd0CfFIcw");

var s_dp = new DocumentProcessing("https://trial.dsserver.io", os);

List<Customer> customers = new List<Customer>();

var customer = new Customer() {
     Company = "Text Control",
     Name = "Jack Petersen"
};

customers.Add(customer);

MergeBody mergeBody = new MergeBody() {
     MergeData = customers,
     MergeSettings = new MergeSettings() {
          Author = "Text Control",
          DocumentTitle = "My Document"
     },
     Template = System.IO.File.ReadAllBytes("App_Data/sample.docx")
};

var results = await s_dp.Merge(mergeBody, ReturnFormat.PDF);