Get Connection String in Azure Function v3

I am very confused. I want to get a connection string in an Azure v3 function (.Net Core 3.1).

My local settings looks like

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "AzureWebJobsDashboard": "UseDevelopmentStorage=true"
    },
    "ConnectionStrings": {
      "DefaultConnection": "bla bla"
    }
}

and in the function I do

string defaultConnection = Environment.GetEnvironmentVariable("ConnectionStrings:DefaultConnection");

This works fine locally but on Azure, defaultConnection is null. I defined the connection under the section Connection strings of the function’s Application Settings.

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Is my approach correct for Azure function v3?

Answer

You need the specify the connection string prefix (see documentation):

Environment.GetEnvironmentVariable("CUSTOMCONNSTR_DefaultConnection");