ASP.NET Core 1.1 runs fine locally but when publishing to Azure says “An error occurred while starting the application.”

Question

I\'ve been developing an ASP.NET Core web app, based largely on the MVC template provided in Visual Studio 2017 RC2. It runs just fine in local debug mode, but when I try to

Answer 1

In my case, it was because I was trying to publish user secrets for use with Fabook OAuth. I know that's a very situational specific answer, but OAuth seems pretty common these day. User Secrets, it turns out, are not meant to be published. Who knew.

So to test this I temporarily changed the following code in startup.cs. This data should be not hard coded as a part of best practice, as it would end up in clear text in source control.

Before

    app.UseFacebookAuthentication(new FacebookOptions()
    {
        AppId = Configuration["Authentication:Facebook:AppId"],
        AppSecret = Configuration["Authentication:Facebook:AppSecret"]
    });

After

    app.UseFacebookAuthentication(new FacebookOptions()
    {
        AppId = "0000000000000", // your value
        AppSecret = "0000000000000000000000000000000" // your value
    });

Then it worked.