{"id":282,"date":"2017-01-05T05:17:33","date_gmt":"2017-01-05T05:17:33","guid":{"rendered":"http:\/\/www.gmass.co\/blog\/?p=282"},"modified":"2019-10-17T14:29:01","modified_gmt":"2019-10-17T14:29:01","slug":"call-the-gmail-api-in-net-without-using-client-library","status":"publish","type":"post","link":"https:\/\/www.gmass.co\/blog\/call-the-gmail-api-in-net-without-using-client-library\/","title":{"rendered":"How to call the Gmail API in .NET without using the client library"},"content":{"rendered":"
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This article is geared towards software developers interested in the Gmail API.<\/i><\/p>\n

GMass makes extensive use of two APIs — the Inbox SDK<\/a> API, made by Streak, and the Gmail API<\/a> provided by Google. The Gmail API manages all of the backend operations for GMass, including applying the “GMass Scheduled” Label to pending campaigns and actually sending a user’s mail merge campaign. GMass is built on the .NET platform and all backend code is written in C#. Google provides a .NET client library for the Gmail API<\/a>, but recently I discovered a bug in the client library that was a show-stopper, until I figured out how to call the Gmail API using raw HTTP calls.<\/p>\n

While the Gmail API asserts\u00a0that a Draft up to 35 MB in size can be created, I was getting an error from the .NET client library anytime I attempted to create a Draft greater than 1 MB in size. The error\u00a0was:<\/p>\n

Message[Request<\/span>\u00a0payload<\/span><\/span>\u00a0size exceeds the limit: 1048576 bytes.]<\/span><\/pre>\n
I would only get this error when creating a large Draft with the .NET library. Testing the Users.drafts.create method manually using the test form provided by Google<\/a> did allow me to create large\u00a0Drafts, which confirmed that the issue was with the .NET library. I therefore set out to create my own function to call the Gmail API to create a Draft and\u00a0bypass the functionality of the client library.<\/p>\n
Like many popular APIs, the Gmail API has an endpoint that you can make an HTTP POST to. In the case of the drafts.Create method, that endpoint is:<\/p>\n
https:\/\/www.googleapis.com\/gmail\/v1\/users\/{EmailAddress}\/drafts<\/pre>\n
where {EmailAddress}<\/strong> is the Gmail account address for which you want to create the Draft.<\/p>\n
Here is the C# code I used to call service.Users.Drafts.Create<\/strong> manually:<\/p>\n
string<\/span> payload = \"{\\n\\\"message\\\": {\\n\"<\/span> + (!string<\/span>.IsNullOrEmpty(ThreadID) ? (\"\\\"threadId\\\":\\\"\"<\/span> + ThreadID + \"\\\",\\n\"<\/span>) : (\"\"<\/span>)) + \"\\\"raw\\\":\\n\\\"\"<\/span> + RawDraft + \"\\\"\\n}\\n}\"<\/span>;<\/span>\r\nusing<\/span> (var<\/span> client = new<\/span> HttpClient<\/span>())<\/span>\r\n{<\/span>\r\n\u00a0 \u00a0 \u00a0 \u00a0<\/span>var<\/span> content = new<\/span> StringContent<\/span>(payload, Encoding<\/span>.Default, \"message\/rfc822\"<\/span>);<\/span>\r\n\r\n\u00a0 \u00a0 \u00a0 \u00a0<\/span>var<\/span> response = client.PostAsync($\"https:\/\/www.googleapis.com\/gmail\/v1\/users\/<\/span>{EmailAddress}\/drafts?access_token=<\/span>{OAuthKey}\"<\/span>, content).Result;<\/span>\r\n\u00a0 \u00a0 \u00a0 \u00a0<\/span>string<\/span> resultContent = response.Content.ReadAsStringAsync().Result;<\/span>\r\n\u00a0 \u00a0 \u00a0 \u00a0<\/span>return<\/span> resultContent;<\/span>\r\n}\r\n<\/span><\/pre>\n
Using the HttpClient object will be familiar to most .NET developers, but the differentiating part of the call is that the mediaType<\/strong> has to be set to “message\/rfc822”, as that is what the Gmail API requires.<\/p>\n
Also note the payload is formatted according to how the payload is formatted on the Google test form for this method<\/a>. In my code it’s assumed that:<\/p>\n