Need to write batch (C#) app to pull Constant Contact data via API

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Hi, I've been tasked with writing a C# program that will run in the middle of the night (unattended) to pull data via the CC API.  Everything seems to be based around OAuth2, but that's terribly complex and I'm not sure it's applicable anyway (this is NOT a web app, and no one will be there to click the "allow access" button).


Can anyone give me some pointers on this?  I'm absolutely NOT an OAuth2 expert, so keep it simple.... thanks

0 Votes

Hello DarleneC93,


Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.


Each of our current OAuth2 authorization flows require the use of a browser to grant access to an application on an account once, at which point an application can utilize refresh tokens to maintain account access without requiring further authorization through a browser window.


We're currently investigating options which would better suit the needs of unattended applications, such as the device authorization flow, however, I’m unable to guarantee if or when this would be implemented. Below I’m including overview documentation for each of our current OAuth2 flows along with some steps to get started with the Authorization Code flow.


OAuth2 Overview:


You should be able to fully automate your integration with the exception of the initial Authorization Request screen and redirect, which can only be accessed/authorized via a browser window and cannot be bypassed, but you should only need to authorize each connected account once.


To get started with the V3 API, you’ll want to start by going through the V3 API OAuth2 Authorization Code Flow. Please note, after step 1, you should set up step 4 before proceeding, because the authorization code from steps 2 and 3 only has a lifespan of 5 minutes.


V3 API OAuth2 Authorization Code Flow


Once you have your first set of tokens, you’ll want to set the access token and the refresh token as values for corresponding variables in your application, so that when your program runs through step 8 of the OAuth2 Authorization Code Flow

to get the new set of tokens it can assign the updated values to those variables to maintain an authenticated connection.


You can either have the application refresh the tokens on a timer based on the life of the access token (access token lifetime is a static 24 hours), or you can check to see if the access token is still active before each submission, and then use the refresh token to generate a new set of tokens if not.


In order to parse the JWT access token for the expiration date/time and/or granted scopes, I'd suggest looking for a standalone JWT decoder tool or setting up a decoder within your program’s code so that it can programmatically verify the remaining lifetime of the access token before attempting to refresh.


[3rd party resource] JWT Decoder Tool Examples:


[3rd party resource] Epoch & Unix Timestamp Conversion Tool Example:


If you want your application to parse the JWT programmatically in your program’s code (the example we currently offer in the documentation is only in Java at this time), you can find instructions online regarding how to do this in different languages.


The OpenID Foundation maintains a list of libraries implementing JWT and JOSE specs, which may be a good starting point. Their list can be found here:


Once authentication is set up, and you’re able to complete Step 8 (Refresh the Access Token), you can then use your current Access Token variable value to make calls to the API endpoints.


Please have a look and let us know if you have any other questions!



John B.
API Support Specialist
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