Add support for .env files

src/Samples/.env

@@ -0,0 +1 @@
+FOO=BAR

src/Samples/Program.cs

@@ -5,6 +5,7 @@
     { "user", "What's Tesla stock worth today? Search X and the news for latest info." },
 };
 
+// Env supports .env as well as all standard .NET configuration sources
 var grok = new GrokClient(Env.Get("XAI_API_KEY")!, new GrokClientOptions()
     .UseJsonConsoleLogging(new() { WrapLength = 80 }));
 

src/Weaving/ConsoleInitializer.cs → src/Weaving/AppInitializer.cs

@@ -4,7 +4,7 @@
 
 namespace Weaving;
 
-class ConsoleInitializer
+class AppInitializer
 {
 #pragma warning disable CA2255 // The 'ModuleInitializer' attribute should not be used in libraries
     [ModuleInitializer]
@@ -13,5 +13,13 @@ public static void Init()
     {
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             Console.InputEncoding = Console.OutputEncoding = Encoding.UTF8;
+
+        // Load environment variables from .env files in current dir and above.
+        DotNetEnv.Env.TraversePath().Load();
+
+        // Load environment variables from user profile directory.
+        var userEnv = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".env");
+        if (File.Exists(userEnv))
+            DotNetEnv.Env.Load(userEnv);
     }
 }

src/Weaving/Weaving.csproj

@@ -10,6 +10,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="DotNetEnv" Version="3.1.1" />
     <PackageReference Include="Microsoft.Extensions.Hosting" Version="9.0.6" />
     <PackageReference Include="NuGetizer" Version="1.2.4" PrivateAssets="all" />
   </ItemGroup>

src/Weaving/Weaving.props

@@ -30,6 +30,7 @@
 
   <ItemGroup>
     <AssemblyMetadata Include="MSBuildProjectName" Value="$(MSBuildProjectName)" />
+    <None Update=".env" CopyToOutputDirectory="PreserveNewest" CopyToPublishDirectory="Never" />
   </ItemGroup>
 
 </Project>

src/Weaving/readme.md

@@ -29,6 +29,21 @@ AnsiConsole.MarkupLine($":robot: {response.Text}");
 > The most useful namespaces and dependencies for developing Microsoft.Extensions.AI-
 > powered applications are automatically referenced and imported when using this package.
 
+## Configuration / Environment Variables
+
+The `Env` class provides access to the following variables/configuration automatically: 
+
+* `.env` files: in local and parent directories
+* `~/.env` file: in the user's home directory (`%userprofile%\.env` on Windows)
+* All default configuration sources from [App Builder](https://learn.microsoft.com/en-us/dotnet/core/extensions/generic-host?tabs=appbuilder#host-builder-settings): 
+    * Environment variables prefixed with DOTNET_.
+    * Command-line arguments.
+    * appsettings.json.
+    * appsettings.{Environment}.json.
+    * Secret Manager when the app runs in the Development environment.
+    * Environment variables.
+    * Command-line arguments.
+
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