文章摘要
本文描述了一个C#类，该类通过配置在`ApplicationPartManager`中的`IApplicationFeatureProvider`实例来填充指定特征。`PopulateFeature`方法遍历所有配置的提供器，将特征应用到指定的应用部分。`PopulateDefaultParts`方法从指定的assemblyName加载assembly，并通过`ApplicationPartAttribute`获取依赖项，将这些应用部分添加到`ApplicationParts`集合中。代码涉及多处依赖项管理，用于确保依赖关系的正确性。
/// <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;
}
}