(.NET Core C#) Send GMail with Attachments

Demonstrates how to send an email containing attachments using the GMail REST API.

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

bool success;

// Use the Chilkat Email API to create or load an email.
Chilkat.Email email = new Chilkat.Email();

// The From name/address don't need to be specified. 
// GMail will automatically use your Gmail address if the following 2 lines are omitted.
email.FromName = "My Name";
email.FromAddress = "my_account_name@gmail.com";

email.AddTo("John Smith","somebody@somewhere.com");
// To add more recipients, make additional calls to AddTo or AddCC, one per recipient...

email.Subject = "This is a test GMail email created using Chilkat.";
email.Charset = "utf-8";
email.AddPlainTextAlternativeBody("This is a test");

// Create an HTML email body with an embedded image.
string cid = email.AddRelatedFile("qa_data/jpg/starfish.jpg");
Chilkat.StringBuilder sbHtml = new Chilkat.StringBuilder();
sbHtml.Append("<html><body>This is a <b>test</b><br><img src=\"cid:STARFISH_CID\"/></body></html>");
int numReplacements = sbHtml.Replace("STARFISH_CID",cid);

email.AddHtmlAlternativeBody(sbHtml.GetAsString());

// Add some attachments..
string mimeType = email.AddFileAttachment("qa_data/helloWorld.pdf");
if (email.LastMethodSuccess != true) {
    Debug.WriteLine("Failed to add PDF attachment.");
    return;
}

mimeType = email.AddFileAttachment("qa_data/msword/sample2.docx");
if (email.LastMethodSuccess != true) {
    Debug.WriteLine("Failed to add MS-Word attachment.");
    return;
}

// OK.. we now have an HTML email with 2 attachments..
Chilkat.StringBuilder sbMime = new Chilkat.StringBuilder();
email.GetMimeSb(sbMime);

// Send the email.  (GMail has a 5MB limit on the total email size.)
Chilkat.Http http = new Chilkat.Http();
http.AuthToken = "GMAIL-ACCESS-TOKEN";

// Send using the simple upload request for the Gmail API
string url = "https://www.googleapis.com/upload/gmail/v1/users/me/messages/send?uploadType=media";
bool sendGzipped = true;
Chilkat.HttpResponse resp = http.PTextSb("POST",url,sbMime,"utf-8","message/rfc822",false,sendGzipped);
if (http.LastMethodSuccess != true) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

// A status code of 200 indicates success.
Debug.WriteLine("Response status code: " + Convert.ToString(resp.StatusCode));
Debug.WriteLine("Response body:");
Debug.WriteLine(resp.BodyStr);

// The response body contains JSON.
// Use the online tool at Generate JSON Parsing Code
// to generate JSON parsing code.

// A sample successful JSON response:

// {
//  "id": "166f0d4ac39e50bf",
//  "threadId": "166f0d4ac39e50bf",
//  "labelIds": [
//   "SENT"
//  ]
// }