I have tried adding DefaultConnection from my appsettings.json file to Azure's Application Settings but Azure will not override the connection string.
Any article or blog I can find states that all I should need to do is add the connection string name as it states in the appsettings.json file and Azure should do the rest (e.g. https://tehremo.wordpress.com/2016/10/07/override-connection-strings-app-settings-in-asp-net-core-and-azure-app-service/) however when the application is published it is using my local connection string.
My Startup.cs file looks like the following:
NOTE: I am publishing using VSTS continuous delivery with "Deploy Azure App Service" release task.
I just had a similar problem (the problem was with PostgreSQL connection string type, I had to change it to custom) and now it works for me, so these are the pieces:
Additional info from my comments below:
Azure GUI (Connection strings, Application settings) uses environment variables internally, so the appsettings.json will stay the same.
If there is a need for an appsettings.json's value to be overwritten during VSTS release activity (before it will be published to Azure), Colin's ALM Corner Build & Release Tools can be used. Here are the links to Colin's ALM Corner Build & Release Tools and tutorial.