I downloaded the sample code for asp.net for "Campaign sample forms" from the following page:
I tried to click on the link on the default.aspx page for "Listing all email campaigns" and I got the error (401) Unauthorized.
The reason I tried this in the first place is that I am trying to create some campaign programmatically and I could not because of the same problem.
So I need help on passing the authentication.
In most cases, 401 errors are a result of an improperly formatted login. Your application will need to construct a HTTP Username from a concatenation of your API User Key, the "%" character and the Constant Contact customer's UserName. This information is passed with Constant Contact Customer's Password.
Please ensure the username you are passing is formatted as follows, where the string of letters preceding the % is your API key:
Support Engineer, Constant Contact