Allow reading connection strings from config

src/Aspire.Hosting/ComponentBuilderExtensions.cs

@@ -2,11 +2,14 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Aspire.Hosting.ApplicationModel;
+using Microsoft.Extensions.Configuration;
 
 namespace Aspire.Hosting;
 
 public static class ComponentBuilderExtensions
 {
+    private const string ConnectionStringEnvironmentName = "ConnectionStrings__";
+
     public static AllocatedEndpointAnnotation? GetEndpoint<T>(this IDistributedApplicationComponentBuilder<T> builder, string name) where T : IDistributedApplicationComponent
     {
         return builder.Component.Annotations.OfType<AllocatedEndpointAnnotation>().SingleOrDefault();
@@ -68,28 +71,32 @@ private static Action<EnvironmentCallbackContext> CreateServiceReferenceEnvironm
         };
     }
 
-    public static IDistributedApplicationComponentBuilder<TDestination> WithReference<TDestination, TSource>(this IDistributedApplicationComponentBuilder<TDestination> builder, IDistributedApplicationComponentBuilder<TSource> source)
+    public static IDistributedApplicationComponentBuilder<TDestination> WithReference<TDestination, TSource>(this IDistributedApplicationComponentBuilder<TDestination> builder, IDistributedApplicationComponentBuilder<TSource> source, string? connectionName = null)
         where TDestination : IDistributedApplicationComponentWithEnvironment
         where TSource : IDistributedApplicationComponentWithConnectionString
     {
-        var connectionName = $"ConnectionStrings__{source.Component.Name}";
+        var component = source.Component;
+        connectionName ??= component.Name;
 
         return builder.WithEnvironment(context =>
         {
+            var connectionStringName = $"{ConnectionStringEnvironmentName}{connectionName}";
+
             if (context.PublisherName == "manifest")
             {
-                context.EnvironmentVariables[connectionName] = $"{{{source.Component.Name}.connectionString}}";
+                context.EnvironmentVariables[connectionStringName] = $"{{{component.Name}.connectionString}}";
                 return;
             }
 
-            var connectionString = source.Component.GetConnectionString();
+            var connectionString = component.GetConnectionString() ??
+                builder.ApplicationBuilder.Configuration.GetConnectionString(component.Name);
 
             if (string.IsNullOrEmpty(connectionString))
             {
-                throw new DistributedApplicationException($"A connection string for '{source.Component.Name}' could not be retrieved.");
+                throw new DistributedApplicationException($"A connection string for '{component.Name}' could not be retrieved.");
             }
 
-            context.EnvironmentVariables[connectionName] = connectionString;
+            context.EnvironmentVariables[connectionStringName] = connectionString;
         });
     }
 

src/Aspire.Hosting/Postgres/PostgresBuilderExtensions.cs

@@ -4,6 +4,7 @@
 using System.Net.Sockets;
 using System.Text.Json;
 using Aspire.Hosting.ApplicationModel;
+using Microsoft.Extensions.Configuration;
 
 namespace Aspire.Hosting.Postgres;
 
@@ -32,7 +33,7 @@ public static IDistributedApplicationComponentBuilder<PostgresContainerComponent
                       });
     }
 
-    public static IDistributedApplicationComponentBuilder<PostgresComponent> AddPostgres(this IDistributedApplicationBuilder builder, string name, string? connectionString)
+    public static IDistributedApplicationComponentBuilder<PostgresComponent> AddPostgres(this IDistributedApplicationBuilder builder, string name, string? connectionString = null)
     {
         var postgres = new PostgresComponent(name, connectionString);
 
@@ -60,7 +61,7 @@ public static IDistributedApplicationComponentBuilder<T> WithPostgresDatabase<T>
         where T : IDistributedApplicationComponentWithEnvironment
     {
         var postgres = postgresBuilder.Component;
-        connectionName = connectionName ?? postgresBuilder.Component.Name;
+        connectionName ??= postgresBuilder.Component.Name;
 
         return builder.WithEnvironment((context) =>
         {
@@ -72,11 +73,14 @@ public static IDistributedApplicationComponentBuilder<T> WithPostgresDatabase<T>
                 return;
             }
 
-            var connectionString = postgres.GetConnectionString(databaseName);
+            var connectionString = postgres.GetConnectionString(databaseName) ??
+                builder.ApplicationBuilder.Configuration.GetConnectionString(postgres.Name);
+
             if (string.IsNullOrEmpty(connectionString))
             {
                 throw new DistributedApplicationException($"A connection string for Postgres '{postgres.Name}' could not be retrieved.");
             }
+
             context.EnvironmentVariables[connectionStringName] = connectionString;
         });
     }

src/Aspire.Hosting/Redis/RedisBuilderExtensions.cs

@@ -20,7 +20,7 @@ public static IDistributedApplicationComponentBuilder<RedisContainerComponent> A
         return componentBuilder;
     }
 
-    public static IDistributedApplicationComponentBuilder<RedisComponent> AddRedis(this IDistributedApplicationBuilder builder, string name, string? connectionString)
+    public static IDistributedApplicationComponentBuilder<RedisComponent> AddRedis(this IDistributedApplicationBuilder builder, string name, string? connectionString = null)
     {
         var redis = new RedisComponent(name, connectionString);
 
@@ -44,6 +44,6 @@ private static void WriteRedisComponentToManifest(Utf8JsonWriter jsonWriter, str
     public static IDistributedApplicationComponentBuilder<T> WithRedis<T>(this IDistributedApplicationComponentBuilder<T> builder, IDistributedApplicationComponentBuilder<IRedisComponent> redisBuilder, string? connectionName = null)
         where T : IDistributedApplicationComponentWithEnvironment
     {
-        return builder.WithReference(redisBuilder);
+        return builder.WithReference(redisBuilder, connectionName);
     }
 }

src/Aspire.Hosting/SqlServer/SqlServerBuilderExtensions.cs

@@ -4,6 +4,7 @@
 using System.Net.Sockets;
 using System.Text.Json;
 using Aspire.Hosting.ApplicationModel;
+using Microsoft.Extensions.Configuration;
 
 namespace Aspire.Hosting.SqlServer;
 
@@ -24,7 +25,7 @@ public static IDistributedApplicationComponentBuilder<SqlServerContainerComponen
         return componentBuilder;
     }
 
-    public static IDistributedApplicationComponentBuilder<SqlServerComponent> AddSqlServer(this IDistributedApplicationBuilder builder, string name, string? connectionString)
+    public static IDistributedApplicationComponentBuilder<SqlServerComponent> AddSqlServer(this IDistributedApplicationBuilder builder, string name, string? connectionString = null)
     {
         var sqlServer = new SqlServerComponent(name, connectionString);
 
@@ -49,7 +50,7 @@ public static IDistributedApplicationComponentBuilder<T> WithSqlServer<T>(this I
         where T : IDistributedApplicationComponentWithEnvironment
     {
         var sql = sqlBuilder.Component;
-        connectionName = connectionName ?? sqlBuilder.Component.Name;
+        connectionName ??= sqlBuilder.Component.Name;
 
         return builder.WithEnvironment((context) =>
         {
@@ -61,11 +62,14 @@ public static IDistributedApplicationComponentBuilder<T> WithSqlServer<T>(this I
                 return;
             }
 
-            var connectionString = sql.GetConnectionString(databaseName);
+            var connectionString = sql.GetConnectionString(databaseName) ??
+                builder.ApplicationBuilder.Configuration.GetConnectionString(sql.Name);
+
             if (string.IsNullOrEmpty(connectionString))
             {
                 throw new DistributedApplicationException($"A connection string for SqlServer '{sql.Name}' could not be retrieved.");
             }
+
             context.EnvironmentVariables[connectionStringName] = connectionString;
         });
     }