Simplify normalization logic to apply to all configuration keys

Co-authored-by: davidfowl <95136+davidfowl@users.noreply.github.com>

Author: Copilot

src/Aspire.Hosting/ParameterResourceBuilderExtensions.cs

@@ -203,17 +203,16 @@ public static IResourceBuilder<ParameterResource> WithCustomInput(this IResource
 
     private static string GetParameterValue(ConfigurationManager configuration, string name, ParameterDefault? parameterDefault, string? configurationKey = null)
     {
-        var useDefaultKey = configurationKey is null;
         configurationKey ??= $"Parameters:{name}";
 
         // First try to get the value with the exact configuration key
         var value = configuration[configurationKey];
 
-        // If not found, the default key was used, and the name contains dashes, try with underscores as a fallback
+        // If not found and the name contains dashes, try with underscores as a fallback
         // This supports command-line arguments and environment variables where dashes are replaced with underscores
-        if (value is null && useDefaultKey && name.Contains('-', StringComparison.Ordinal))
+        if (value is null)
         {
-            var normalizedKey = $"Parameters:{name.Replace("-", "_", StringComparison.Ordinal)}";
+            var normalizedKey = configurationKey.Replace("-", "_", StringComparison.Ordinal);
             value = configuration[normalizedKey];
         }
 

tests/Aspire.Hosting.Tests/AddParameterTests.cs

@@ -581,7 +581,7 @@ public void ParameterWithoutDash_DoesNotFallbackToUnderscore()
     }
 
     [Fact]
-    public void ParameterWithCustomConfigurationKey_DoesNotUseFallback()
+    public void ParameterWithCustomConfigurationKey_UsesFallback()
     {
         // Arrange
         var appBuilder = DistributedApplication.CreateBuilder();
@@ -592,14 +592,14 @@ public void ParameterWithCustomConfigurationKey_DoesNotUseFallback()
             ["CustomSection:my_key"] = "custom-value"
         });
 
-        // Act - use custom configuration key
+        // Act - use custom configuration key with dash
         appBuilder.AddParameterFromConfiguration("my-param", "CustomSection:my-key");
 
         using var app = appBuilder.Build();
         var appModel = app.Services.GetRequiredService<DistributedApplicationModel>();
         var parameterResource = Assert.Single(appModel.Resources.OfType<ParameterResource>());
 
-        // Assert - should find the value using the custom key without any fallback logic
+        // Assert - should find the value using the normalized key (dash -> underscore)
 #pragma warning disable CS0618 // Type or member is obsolete
         Assert.Equal("custom-value", parameterResource.Value);
 #pragma warning restore CS0618 // Type or member is obsolete