App on Azure or local check

ExecutionContextExtension.cs

using Microsoft.Azure.WebJobs;
using System;

namespace MyFunction.Extensions
{
    public static class ExecutionContextExtension
    {
        public static bool IsAzureEnvironment(this ExecutionContext context, string environmentVariable = "WEBSITE_INSTANCE_ID")
        {
            var isAzureEnvironment = !string.IsNullOrEmpty(Environment.GetEnvironmentVariable(environmentVariable, EnvironmentVariableTarget.Process));
            return isAzureEnvironment;
        }
    }
}