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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Linq;
using System.Reflection;
namespace Microsoft.AspNetCore.Mvc.ApplicationParts;
/// <summary>
/// Manages the parts and features of an MVC application.
/// </summary>
public class ApplicationPartManager
{
/// <summary>
/// Gets the list of <see cref="IApplicationFeatureProvider"/>s.
/// </summary>
public IList<IApplicationFeatureProvider> FeatureProviders { get; } =
new List<IApplicationFeatureProvider>();
/// <summary>
/// Gets the list of <see cref="ApplicationPart"/> instances.
/// <para>
/// Instances in this collection are stored in precedence order. An <see cref="ApplicationPart"/> that appears
/// earlier in the list has a higher precedence.
/// An <see cref="IApplicationFeatureProvider"/> may choose to use this an interface as a way to resolve conflicts when
/// multiple <see cref="ApplicationPart"/> instances resolve equivalent feature values.
/// </para>
/// </summary>
public IList<ApplicationPart> ApplicationParts { get; } = new List<ApplicationPart>();
/// <summary>
/// Populates the given <paramref name="feature"/> using the list of
/// <see cref="IApplicationFeatureProvider{TFeature}"/>s configured on the
/// <see cref="ApplicationPartManager"/>.
/// </summary>
/// <typeparam name="TFeature">The type of the feature.</typeparam>
/// <param name="feature">The feature instance to populate.</param>
public void PopulateFeature<TFeature>(TFeature feature)
{
if (feature == null)
{
throw new ArgumentNullException(nameof(feature));
}
foreach (var provider in FeatureProviders.OfType<IApplicationFeatureProvider<TFeature>>())
{
provider.PopulateFeature(ApplicationParts, feature);
}
}
internal void PopulateDefaultParts(string entryAssemblyName)
{
var assemblies = GetApplicationPartAssemblies(entryAssemblyName);
var seenAssemblies = new HashSet<Assembly>();
foreach (var assembly in assemblies)
{
if (!seenAssemblies.Add(assembly))
{
// "assemblies" may contain duplicate values, but we want unique ApplicationPart instances.
// Note that we prefer using a HashSet over Distinct since the latter isn't
// guaranteed to preserve the original ordering.
continue;
}
var partFactory = ApplicationPartFactory.GetApplicationPartFactory(assembly);
foreach (var applicationPart in partFactory.GetApplicationParts(assembly))
{
ApplicationParts.Add(applicationPart);
}
}
}
private static IEnumerable<Assembly> GetApplicationPartAssemblies(string entryAssemblyName)
{
var entryAssembly = Assembly.Load(new AssemblyName(entryAssemblyName));
// Use ApplicationPartAttribute to get the closure of direct or transitive dependencies
// that reference MVC.
var assembliesFromAttributes = entryAssembly.GetCustomAttributes<ApplicationPartAttribute>()
.Select(name => Assembly.Load(name.AssemblyName))
.OrderBy(assembly => assembly.FullName, StringComparer.Ordinal)
.SelectMany(GetAssemblyClosure);
// The SDK will not include the entry assembly as an application part. We'll explicitly list it
// and have it appear before all other assemblies \ ApplicationParts.
return GetAssemblyClosure(entryAssembly)
.Concat(assembliesFromAttributes);
}
private static IEnumerable<Assembly> GetAssemblyClosure(Assembly assembly)
{
yield return assembly;
var relatedAssemblies = RelatedAssemblyAttribute.GetRelatedAssemblies(assembly, throwOnError: false)
.OrderBy(assembly => assembly.FullName, StringComparer.Ordinal);
foreach (var relatedAssembly in relatedAssemblies)
{
yield return relatedAssembly;
}
}
}
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