(.NET Core C#) Download GMail Message Attachment by ID

Demonstrates how to download a GMail email attachment by the attachment ID.

For more information, see https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get

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

Chilkat.Http http = new Chilkat.Http();
bool success;

http.AuthToken = "ACCESS_TOKEN";
http.Accept = "application/json";

// See the following example:  Get GMail Message (format=full)
// It shows how to download an email by message ID, and it shows how to parse the JSON
// response which includes attachment names, ids, and other information.

// This example will assume we already have the attachment id and filename.

// This is the attachment ID for a file named "helloWorld.pdf".
string attachmentId = "ANGjdJ-oy3aCuZISJKLAhUdaEksCEklbAPyMaWzFgqOMGbPCRkgwgeu_Kttd99C17OBTHROkDZGekibTKWXGfscB5ww7fw4E65_V1dQ-jHhb2TD1Cdm58-BbNw2iDxzptco8iILPiSnLLfFn5Ps7nsRcxHaGTt3r0yqFKCuIYNnPK1vM04BXI_cfzo-HnI4I3tD6oHNHOGVQrL01MdShFQjPELPUjXM8z1qs7Kom-QyvV1iOldUN-66UuhynsmDX-CMM5TIdB-8KD_lmdhf-0DqG8JnCA20XpXyfqwS8XFkPA-t-QSjb7SdkHQFtQ4lz2PcBREFzZ2eI5j0l0Y_dQHRPYTeMwkVl1yl4MfFT4C4iso3VSF-eqaIjiFCbXKCFNyeEIW5WFsv189dhlSqU";

string messageId = "1712bc1dc22da2a2";

http.SetUrlVar("messageId",messageId);
http.SetUrlVar("attachmentId",attachmentId);

string url = "https://www.googleapis.com/gmail/v1/users/userId/messages/{$messageId}/attachments/{$attachmentId}";

// When we download, the response is JSON that contains the attachment data base64url encoded, like this:
// {
//  "size": 934,
//  "data": "JVBERi0xLjM ... CiUlRU9GCg=="
// }

string outputFilePath = "qa_output/helloWorld.pdf";

// Download into a StringBuilder.
Chilkat.StringBuilder sbJson = new Chilkat.StringBuilder();
success = http.DownloadSb(url,"utf-8",sbJson);
if (success == false) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

if (http.LastStatus != 200) {
    // Something failed.
    // the JSON contains an error message.
    Debug.WriteLine(sbJson.GetAsString());
    return;
}

// Load into a Chilkat JSON object.
Chilkat.JsonObject json = new Chilkat.JsonObject();
success = json.LoadSb(sbJson);

// Extract the base64url data into a BinData.
Chilkat.BinData bd = new Chilkat.BinData();
success = json.BytesOf("data","base64url",bd);

// Save the data to a file.
success = bd.WriteFile("qa_output/helloWorld.pdf");

Debug.WriteLine("Success.");