Adds code

Core/Configurations/ConfigurationManager.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Extensions.Configuration;
+
+namespace Core.Configurations
+{
+	public class ConfigurationManager
+	{
+		private static IConfigurationBuilder _configurationBuilder;
+
+		/// <summary>
+		/// This AppConfigBuilder assumes that AppConfigEndpoint and AppConfigLabelFilter are configured as Settings on Azure for the Application that needs them.
+		/// AppConfigEndpoint would look like this: Endpoint=https://config-dec-test.azconfig.io;Id=0-l9-s0:foo;Secret=somesecret/bar
+		/// </summary>
+		/// <param name="localSettingsFile">
+		///     Path relative to the base path stored in Microsoft.Extensions.Configuration.IConfigurationBuilder.Properties of builder.
+		///  </param>
+		public static IConfigurationBuilder AppConfigBuilder(string localSettingsFile)
+		{
+			if (_configurationBuilder == null)
+			{
+				var envConfiguration = new ConfigurationBuilder()
+					.AddEnvironmentVariables()
+					.Build();
+
+				System.Diagnostics.Trace.Listeners.Add(new System.Diagnostics.TextWriterTraceListener(Console.Out));
+
+				var appConfigEndpoint = envConfiguration["AppConfigEndpoint"];
+				var appConfigLabel = envConfiguration["AppConfigLabelFilter"];
+
+				_configurationBuilder = new ConfigurationBuilder();
+				if (!string.IsNullOrEmpty(appConfigEndpoint))
+				{
+					_configurationBuilder
+						.AddAzureAppConfiguration(options =>
+						{
+							options.Connect(appConfigEndpoint);
+							options.Select(keyFilter: "*", labelFilter: appConfigLabel);
+						})
+						.AddEnvironmentVariables();
+				}
+				else
+				{
+					_configurationBuilder.SetBasePath(Directory.GetCurrentDirectory());
+					_configurationBuilder.AddJsonFile(localSettingsFile, optional: false);
+				}
+			}
+			return _configurationBuilder;
+		}
+	}
+}