ASP.NET Core 中间件(Middleware)的使用及其源码解析（二）- 使用UseMiddle - ToB企服应用市场:ToB评测及商务社交产业平台

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using NETCoreMiddleware.Middlewares;
namespace NETCoreMiddleware
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
//服务注册（往容器中添加服务）
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllersWithViews();
}
/// <summary>
/// 配置Http请求处理管道
/// Http请求管道模型---就是Http请求被处理的步骤
/// 所谓管道，就是拿着HttpContext，经过多个步骤的加工，生成Response，这就是管道
/// </summary>
/// <param name="app"></param>
/// <param name="env"></param>
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
#region 环境参数
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
}
#endregion 环境参数
//静态文件中间件
app.UseStaticFiles();
#region Use中间件
//中间件1
app.Use(next =>
{
Console.WriteLine("middleware 1");
return async context =>
{
await Task.Run(() =>
{
Console.WriteLine("");
Console.WriteLine("===================================Middleware===================================");
Console.WriteLine($"This is middleware 1 Start");
});
await next.Invoke(context);
await Task.Run(() =>
{
Console.WriteLine($"This is middleware 1 End");
Console.WriteLine("===================================Middleware===================================");
});
};
});
//中间件2
app.Use(next =>
{
Console.WriteLine("middleware 2");
return async context =>
{
await Task.Run(() => Console.WriteLine($"This is middleware 2 Start"));
await next.Invoke(context); //可通过不调用 next 参数使请求管道短路
await Task.Run(() => Console.WriteLine($"This is middleware 2 End"));
};
});
//中间件3
app.Use(next =>
{
Console.WriteLine("middleware 3");
return async context =>
{
await Task.Run(() => Console.WriteLine($"This is middleware 3 Start"));
await next.Invoke(context);
await Task.Run(() => Console.WriteLine($"This is middleware 3 End"));
};
});
//中间件4
//Use方法的另外一个重载
app.Use(async (context, next) =>
{
await Task.Run(() => Console.WriteLine($"This is middleware 4 Start"));
await next();
await Task.Run(() => Console.WriteLine($"This is middleware 4 End"));
});
#endregion Use中间件
#region UseMiddleware中间件
app.UseMiddleware<CustomMiddleware>();
#endregion UseMiddleware中间件
#region 终端中间件
//app.Use(_ => handler);
app.Run(async context =>
{
await Task.Run(() => Console.WriteLine($"This is Run"));
});
#endregion 终端中间件
#region 最终把请求交给MVC
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "areas",
pattern: "{area:exists}/{controller=Home}/{action=Index}/{id?}");
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
});
#endregion 最终把请求交给MVC
}
}
}

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// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Abstractions;
using Microsoft.Extensions.Internal;
namespace Microsoft.AspNetCore.Builder
{
/// <summary>
/// Extension methods for adding typed middleware.
/// </summary>
public static class UseMiddlewareExtensions
{
internal const string InvokeMethodName = "Invoke";
internal const string InvokeAsyncMethodName = "InvokeAsync";
private static readonly MethodInfo GetServiceInfo = typeof(UseMiddlewareExtensions).GetMethod(nameof(GetService), BindingFlags.NonPublic | BindingFlags.Static);
/// <summary>
/// Adds a middleware type to the application's request pipeline.
/// </summary>
/// <typeparam name="TMiddleware">The middleware type.</typeparam>
/// <param name="app">The <see cref="IApplicationBuilder"/> instance.</param>
/// <param name="args">The arguments to pass to the middleware type instance's constructor.</param>
/// <returns>The <see cref="IApplicationBuilder"/> instance.</returns>
public static IApplicationBuilder UseMiddleware<TMiddleware>(this IApplicationBuilder app, params object[] args)
{
return app.UseMiddleware(typeof(TMiddleware), args);
}
/// <summary>
/// Adds a middleware type to the application's request pipeline.
/// </summary>
/// <param name="app">The <see cref="IApplicationBuilder"/> instance.</param>
/// <param name="middleware">The middleware type.</param>
/// <param name="args">The arguments to pass to the middleware type instance's constructor.</param>
/// <returns>The <see cref="IApplicationBuilder"/> instance.</returns>
public static IApplicationBuilder UseMiddleware(this IApplicationBuilder app, Type middleware, params object[] args)
{
if (typeof(IMiddleware).GetTypeInfo().IsAssignableFrom(middleware.GetTypeInfo()))
{
// IMiddleware doesn't support passing args directly since it's
// activated from the container
if (args.Length > 0)
{
throw new NotSupportedException(Resources.FormatException_UseMiddlewareExplicitArgumentsNotSupported(typeof(IMiddleware)));
}
return UseMiddlewareInterface(app, middleware);
}
var applicationServices = app.ApplicationServices;
return app.Use(next =>
{
var methods = middleware.GetMethods(BindingFlags.Instance | BindingFlags.Public);
var invokeMethods = methods.Where(m =>
string.Equals(m.Name, InvokeMethodName, StringComparison.Ordinal)
|| string.Equals(m.Name, InvokeAsyncMethodName, StringComparison.Ordinal)
).ToArray();
if (invokeMethods.Length > 1)
{
throw new InvalidOperationException(Resources.FormatException_UseMiddleMutlipleInvokes(InvokeMethodName, InvokeAsyncMethodName));
}
if (invokeMethods.Length == 0)
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareNoInvokeMethod(InvokeMethodName, InvokeAsyncMethodName, middleware));
}
var methodInfo = invokeMethods[0];
if (!typeof(Task).IsAssignableFrom(methodInfo.ReturnType))
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareNonTaskReturnType(InvokeMethodName, InvokeAsyncMethodName, nameof(Task)));
}
var parameters = methodInfo.GetParameters();
if (parameters.Length == 0 || parameters[0].ParameterType != typeof(HttpContext))
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareNoParameters(InvokeMethodName, InvokeAsyncMethodName, nameof(HttpContext)));
}
var ctorArgs = new object[args.Length + 1];
ctorArgs[0] = next;
Array.Copy(args, 0, ctorArgs, 1, args.Length);
var instance = ActivatorUtilities.CreateInstance(app.ApplicationServices, middleware, ctorArgs);
if (parameters.Length == 1)
{
return (RequestDelegate)methodInfo.CreateDelegate(typeof(RequestDelegate), instance);
}
var factory = Compile<object>(methodInfo, parameters);
return context =>
{
var serviceProvider = context.RequestServices ?? applicationServices;
if (serviceProvider == null)
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareIServiceProviderNotAvailable(nameof(IServiceProvider)));
}
return factory(instance, context, serviceProvider);
};
});
}
private static IApplicationBuilder UseMiddlewareInterface(IApplicationBuilder app, Type middlewareType)
{
return app.Use(next =>
{
return async context =>
{
var middlewareFactory = (IMiddlewareFactory)context.RequestServices.GetService(typeof(IMiddlewareFactory));
if (middlewareFactory == null)
{
// No middleware factory
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareNoMiddlewareFactory(typeof(IMiddlewareFactory)));
}
var middleware = middlewareFactory.Create(middlewareType);
if (middleware == null)
{
// The factory returned null, it's a broken implementation
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareUnableToCreateMiddleware(middlewareFactory.GetType(), middlewareType));
}
try
{
await middleware.InvokeAsync(context, next);
}
finally
{
middlewareFactory.Release(middleware);
}
};
});
}
private static Func<T, HttpContext, IServiceProvider, Task> Compile<T>(MethodInfo methodInfo, ParameterInfo[] parameters)
{
// If we call something like
//
// public class Middleware
// {
// public Task Invoke(HttpContext context, ILoggerFactory loggerFactory)
// {
//
// }
// }
//
// We'll end up with something like this:
// Generic version:
//
// Task Invoke(Middleware instance, HttpContext httpContext, IServiceProvider provider)
// {
// return instance.Invoke(httpContext, (ILoggerFactory)UseMiddlewareExtensions.GetService(provider, typeof(ILoggerFactory));
// }
// Non generic version:
//
// Task Invoke(object instance, HttpContext httpContext, IServiceProvider provider)
// {
// return ((Middleware)instance).Invoke(httpContext, (ILoggerFactory)UseMiddlewareExtensions.GetService(provider, typeof(ILoggerFactory));
// }
var middleware = typeof(T);
var httpContextArg = Expression.Parameter(typeof(HttpContext), "httpContext");
var providerArg = Expression.Parameter(typeof(IServiceProvider), "serviceProvider");
var instanceArg = Expression.Parameter(middleware, "middleware");
var methodArguments = new Expression[parameters.Length];
methodArguments[0] = httpContextArg;
for (int i = 1; i < parameters.Length; i++)
{
var parameterType = parameters[i].ParameterType;
if (parameterType.IsByRef)
{
throw new NotSupportedException(Resources.FormatException_InvokeDoesNotSupportRefOrOutParams(InvokeMethodName));
}
var parameterTypeExpression = new Expression[]
{
providerArg,
Expression.Constant(parameterType, typeof(Type)),
Expression.Constant(methodInfo.DeclaringType, typeof(Type))
};
var getServiceCall = Expression.Call(GetServiceInfo, parameterTypeExpression);
methodArguments[i] = Expression.Convert(getServiceCall, parameterType);
}
Expression middlewareInstanceArg = instanceArg;
if (methodInfo.DeclaringType != typeof(T))
{
middlewareInstanceArg = Expression.Convert(middlewareInstanceArg, methodInfo.DeclaringType);
}
var body = Expression.Call(middlewareInstanceArg, methodInfo, methodArguments);
var lambda = Expression.Lambda<Func<T, HttpContext, IServiceProvider, Task>>(body, instanceArg, httpContextArg, providerArg);
return lambda.Compile();
}
private static object GetService(IServiceProvider sp, Type type, Type middleware)
{
var service = sp.GetService(type);
if (service == null)
{
throw new InvalidOperationException(Resources.FormatException_InvokeMiddlewareNoService(type, middleware));
}
return service;
}
}
}

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/// <summary>
/// Adds a middleware type to the application's request pipeline.
/// </summary>
/// <param name="app">The <see cref="IApplicationBuilder"/> instance.</param>
/// <param name="middleware">The middleware type.</param>
/// <param name="args">The arguments to pass to the middleware type instance's constructor.</param>
/// <returns>The <see cref="IApplicationBuilder"/> instance.</returns>
public static IApplicationBuilder UseMiddleware(this IApplicationBuilder app, Type middleware, params object[] args)
{
if (typeof(IMiddleware).GetTypeInfo().IsAssignableFrom(middleware.GetTypeInfo()))
{
// IMiddleware doesn't support passing args directly since it's
// activated from the container
if (args.Length > 0)
{
throw new NotSupportedException(Resources.FormatException_UseMiddlewareExplicitArgumentsNotSupported(typeof(IMiddleware)));
}
return UseMiddlewareInterface(app, middleware);
}
var applicationServices = app.ApplicationServices;
return app.Use(next =>
{
var methods = middleware.GetMethods(BindingFlags.Instance | BindingFlags.Public);
var invokeMethods = methods.Where(m =>
string.Equals(m.Name, InvokeMethodName, StringComparison.Ordinal)
|| string.Equals(m.Name, InvokeAsyncMethodName, StringComparison.Ordinal)
).ToArray();
if (invokeMethods.Length > 1)
{
throw new InvalidOperationException(Resources.FormatException_UseMiddleMutlipleInvokes(InvokeMethodName, InvokeAsyncMethodName));
}
if (invokeMethods.Length == 0)
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareNoInvokeMethod(InvokeMethodName, InvokeAsyncMethodName, middleware));
}
var methodInfo = invokeMethods[0];
if (!typeof(Task).IsAssignableFrom(methodInfo.ReturnType))
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareNonTaskReturnType(InvokeMethodName, InvokeAsyncMethodName, nameof(Task)));
}
var parameters = methodInfo.GetParameters();
if (parameters.Length == 0 || parameters[0].ParameterType != typeof(HttpContext))
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareNoParameters(InvokeMethodName, InvokeAsyncMethodName, nameof(HttpContext)));
}
var ctorArgs = new object[args.Length + 1];
ctorArgs[0] = next;
Array.Copy(args, 0, ctorArgs, 1, args.Length);
var instance = ActivatorUtilities.CreateInstance(app.ApplicationServices, middleware, ctorArgs);
if (parameters.Length == 1)
{
return (RequestDelegate)methodInfo.CreateDelegate(typeof(RequestDelegate), instance);
}
var factory = Compile<object>(methodInfo, parameters);
return context =>
{
var serviceProvider = context.RequestServices ?? applicationServices;
if (serviceProvider == null)
{
throw new InvalidOperationException(Resources.FormatException_UseMiddlewareIServiceProviderNotAvailable(nameof(IServiceProvider)));
}
return factory(instance, context, serviceProvider);
};
});
}

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// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Runtime.ExceptionServices;
#if ActivatorUtilities_In_DependencyInjection
using Microsoft.Extensions.Internal;
namespace Microsoft.Extensions.DependencyInjection
#else
namespace Microsoft.Extensions.Internal
#endif
{
/// <summary>
/// Helper code for the various activator services.
/// </summary>
#if ActivatorUtilities_In_DependencyInjection
public
#else
// Do not take a dependency on this class unless you are explicitly trying to avoid taking a
// dependency on Microsoft.AspNetCore.DependencyInjection.Abstractions.
internal
#endif
static class ActivatorUtilities
{
private static readonly MethodInfo GetServiceInfo =
GetMethodInfo<Func<IServiceProvider, Type, Type, bool, object>>((sp, t, r, c) => GetService(sp, t, r, c));
/// <summary>
/// Instantiate a type with constructor arguments provided directly and/or from an <see cref="IServiceProvider"/>.
/// </summary>
/// <param name="provider">The service provider used to resolve dependencies</param>
/// <param name="instanceType">The type to activate</param>
/// <param name="parameters">Constructor arguments not provided by the <paramref name="provider"/>.</param>
/// <returns>An activated object of type instanceType</returns>
public static object CreateInstance(IServiceProvider provider, Type instanceType, params object[] parameters)
{
int bestLength = -1;
var seenPreferred = false;
ConstructorMatcher bestMatcher = default;
if (!instanceType.GetTypeInfo().IsAbstract)
{
foreach (var constructor in instanceType
.GetTypeInfo()
.DeclaredConstructors)
{
if (!constructor.IsStatic && constructor.IsPublic)
{
var matcher = new ConstructorMatcher(constructor);
var isPreferred = constructor.IsDefined(typeof(ActivatorUtilitiesConstructorAttribute), false);
var length = matcher.Match(parameters);
if (isPreferred)
{
if (seenPreferred)
{
ThrowMultipleCtorsMarkedWithAttributeException();
}
if (length == -1)
{
ThrowMarkedCtorDoesNotTakeAllProvidedArguments();
}
}
if (isPreferred || bestLength < length)
{
bestLength = length;
bestMatcher = matcher;
}
seenPreferred |= isPreferred;
}
}
}
if (bestLength == -1)
{
var message = $"A suitable constructor for type '{instanceType}' could not be located. Ensure the type is concrete and services are registered for all parameters of a public constructor.";
throw new InvalidOperationException(message);
}
return bestMatcher.CreateInstance(provider);
}
/// <summary>
/// Create a delegate that will instantiate a type with constructor arguments provided directly
/// and/or from an <see cref="IServiceProvider"/>.
/// </summary>
/// <param name="instanceType">The type to activate</param>
/// <param name="argumentTypes">
/// The types of objects, in order, that will be passed to the returned function as its second parameter
/// </param>
/// <returns>
/// A factory that will instantiate instanceType using an <see cref="IServiceProvider"/>
/// and an argument array containing objects matching the types defined in argumentTypes
/// </returns>
public static ObjectFactory CreateFactory(Type instanceType, Type[] argumentTypes)
{
FindApplicableConstructor(instanceType, argumentTypes, out ConstructorInfo constructor, out int?[] parameterMap);
var provider = Expression.Parameter(typeof(IServiceProvider), "provider");
var argumentArray = Expression.Parameter(typeof(object[]), "argumentArray");
var factoryExpressionBody = BuildFactoryExpression(constructor, parameterMap, provider, argumentArray);
var factoryLamda = Expression.Lambda<Func<IServiceProvider, object[], object>>(
factoryExpressionBody, provider, argumentArray);
var result = factoryLamda.Compile();
return result.Invoke;
}
/// <summary>
/// Instantiate a type with constructor arguments provided directly and/or from an <see cref="IServiceProvider"/>.
/// </summary>
/// <typeparam name="T">The type to activate</typeparam>
/// <param name="provider">The service provider used to resolve dependencies</param>
/// <param name="parameters">Constructor arguments not provided by the <paramref name="provider"/>.</param>
/// <returns>An activated object of type T</returns>
public static T CreateInstance<T>(IServiceProvider provider, params object[] parameters)
{
return (T)CreateInstance(provider, typeof(T), parameters);
}
/// <summary>
/// Retrieve an instance of the given type from the service provider. If one is not found then instantiate it directly.
/// </summary>
/// <typeparam name="T">The type of the service</typeparam>
/// <param name="provider">The service provider used to resolve dependencies</param>
/// <returns>The resolved service or created instance</returns>
public static T GetServiceOrCreateInstance<T>(IServiceProvider provider)
{
return (T)GetServiceOrCreateInstance(provider, typeof(T));
}
/// <summary>
/// Retrieve an instance of the given type from the service provider. If one is not found then instantiate it directly.
/// </summary>
/// <param name="provider">The service provider</param>
/// <param name="type">The type of the service</param>
/// <returns>The resolved service or created instance</returns>
public static object GetServiceOrCreateInstance(IServiceProvider provider, Type type)
{
return provider.GetService(type) ?? CreateInstance(provider, type);
}
private static MethodInfo GetMethodInfo<T>(Expression<T> expr)
{
var mc = (MethodCallExpression)expr.Body;
return mc.Method;
}
private static object GetService(IServiceProvider sp, Type type, Type requiredBy, bool isDefaultParameterRequired)
{
var service = sp.GetService(type);
if (service == null && !isDefaultParameterRequired)
{
var message = $"Unable to resolve service for type '{type}' while attempting to activate '{requiredBy}'.";
throw new InvalidOperationException(message);
}
return service;
}
private static Expression BuildFactoryExpression(
ConstructorInfo constructor,
int?[] parameterMap,
Expression serviceProvider,
Expression factoryArgumentArray)
{
var constructorParameters = constructor.GetParameters();
var constructorArguments = new Expression[constructorParameters.Length];
for (var i = 0; i < constructorParameters.Length; i++)
{
var constructorParameter = constructorParameters[i];
var parameterType = constructorParameter.ParameterType;
var hasDefaultValue = ParameterDefaultValue.TryGetDefaultValue(constructorParameter, out var defaultValue);
if (parameterMap[i] != null)
{
constructorArguments[i] = Expression.ArrayAccess(factoryArgumentArray, Expression.Constant(parameterMap[i]));
}
else
{
var parameterTypeExpression = new Expression[] { serviceProvider,
Expression.Constant(parameterType, typeof(Type)),
Expression.Constant(constructor.DeclaringType, typeof(Type)),
Expression.Constant(hasDefaultValue) };
constructorArguments[i] = Expression.Call(GetServiceInfo, parameterTypeExpression);
}
// Support optional constructor arguments by passing in the default value
// when the argument would otherwise be null.
if (hasDefaultValue)
{
var defaultValueExpression = Expression.Constant(defaultValue);
constructorArguments[i] = Expression.Coalesce(constructorArguments[i], defaultValueExpression);
}
constructorArguments[i] = Expression.Convert(constructorArguments[i], parameterType);
}
return Expression.New(constructor, constructorArguments);
}
private static void FindApplicableConstructor(
Type instanceType,
Type[] argumentTypes,
out ConstructorInfo matchingConstructor,
out int?[] parameterMap)
{
matchingConstructor = null;
parameterMap = null;
if (!TryFindPreferredConstructor(instanceType, argumentTypes, ref matchingConstructor, ref parameterMap) &&
!TryFindMatchingConstructor(instanceType, argumentTypes, ref matchingConstructor, ref parameterMap))
{
var message = $"A suitable constructor for type '{instanceType}' could not be located. Ensure the type is concrete and services are registered for all parameters of a public constructor.";
throw new InvalidOperationException(message);
}
}
// Tries to find constructor based on provided argument types
private static bool TryFindMatchingConstructor(
Type instanceType,
Type[] argumentTypes,
ref ConstructorInfo matchingConstructor,
ref int?[] parameterMap)
{
foreach (var constructor in instanceType.GetTypeInfo().DeclaredConstructors)
{
if (constructor.IsStatic || !constructor.IsPublic)
{
continue;
}
if (TryCreateParameterMap(constructor.GetParameters(), argumentTypes, out int?[] tempParameterMap))
{
if (matchingConstructor != null)
{
throw new InvalidOperationException($"Multiple constructors accepting all given argument types have been found in type '{instanceType}'. There should only be one applicable constructor.");
}
matchingConstructor = constructor;
parameterMap = tempParameterMap;
}
}
return matchingConstructor != null;
}
// Tries to find constructor marked with ActivatorUtilitiesConstructorAttribute
private static bool TryFindPreferredConstructor(
Type instanceType,
Type[] argumentTypes,
ref ConstructorInfo matchingConstructor,
ref int?[] parameterMap)
{
var seenPreferred = false;
foreach (var constructor in instanceType.GetTypeInfo().DeclaredConstructors)
{
if (constructor.IsStatic || !constructor.IsPublic)
{
continue;
}
if (constructor.IsDefined(typeof(ActivatorUtilitiesConstructorAttribute), false))
{
if (seenPreferred)
{
ThrowMultipleCtorsMarkedWithAttributeException();
}
if (!TryCreateParameterMap(constructor.GetParameters(), argumentTypes, out int?[] tempParameterMap))
{
ThrowMarkedCtorDoesNotTakeAllProvidedArguments();
}
matchingConstructor = constructor;
parameterMap = tempParameterMap;
seenPreferred = true;
}
}
return matchingConstructor != null;
}
// Creates an injective parameterMap from givenParameterTypes to assignable constructorParameters.
// Returns true if each given parameter type is assignable to a unique; otherwise, false.
private static bool TryCreateParameterMap(ParameterInfo[] constructorParameters, Type[] argumentTypes, out int?[] parameterMap)
{
parameterMap = new int?[constructorParameters.Length];
for (var i = 0; i < argumentTypes.Length; i++)
{
var foundMatch = false;
var givenParameter = argumentTypes[i].GetTypeInfo();
for (var j = 0; j < constructorParameters.Length; j++)
{
if (parameterMap[j] != null)
{
// This ctor parameter has already been matched
continue;
}
if (constructorParameters[j].ParameterType.GetTypeInfo().IsAssignableFrom(givenParameter))
{
foundMatch = true;
parameterMap[j] = i;
break;
}
}
if (!foundMatch)
{
return false;
}
}
return true;
}
private struct ConstructorMatcher
{
private readonly ConstructorInfo _constructor;
private readonly ParameterInfo[] _parameters;
private readonly object[] _parameterValues;
public ConstructorMatcher(ConstructorInfo constructor)
{
_constructor = constructor;
_parameters = _constructor.GetParameters();
_parameterValues = new object[_parameters.Length];
}
public int Match(object[] givenParameters)
{
var applyIndexStart = 0;
var applyExactLength = 0;
for (var givenIndex = 0; givenIndex != givenParameters.Length; givenIndex++)
{
var givenType = givenParameters[givenIndex]?.GetType().GetTypeInfo();
var givenMatched = false;
for (var applyIndex = applyIndexStart; givenMatched == false && applyIndex != _parameters.Length; ++applyIndex)
{
if (_parameterValues[applyIndex] == null &&
_parameters[applyIndex].ParameterType.GetTypeInfo().IsAssignableFrom(givenType))
{
givenMatched = true;
_parameterValues[applyIndex] = givenParameters[givenIndex];
if (applyIndexStart == applyIndex)
{
applyIndexStart++;
if (applyIndex == givenIndex)
{
applyExactLength = applyIndex;
}
}
}
}
if (givenMatched == false)
{
return -1;
}
}
return applyExactLength;
}
public object CreateInstance(IServiceProvider provider)
{
for (var index = 0; index != _parameters.Length; index++)
{
if (_parameterValues[index] == null)
{
var value = provider.GetService(_parameters[index].ParameterType);
if (value == null)
{
if (!ParameterDefaultValue.TryGetDefaultValue(_parameters[index], out var defaultValue))
{
throw new InvalidOperationException($"Unable to resolve service for type '{_parameters[index].ParameterType}' while attempting to activate '{_constructor.DeclaringType}'.");
}
else
{
_parameterValues[index] = defaultValue;
}
}
else
{
_parameterValues[index] = value;
}
}
}
#if NETCOREAPP
return _constructor.Invoke(BindingFlags.DoNotWrapExceptions, binder: null, parameters: _parameterValues, culture: null);
#else
try
{
return _constructor.Invoke(_parameterValues);
}
catch (TargetInvocationException ex) when (ex.InnerException != null)
{
ExceptionDispatchInfo.Capture(ex.InnerException).Throw();
// The above line will always throw, but the compiler requires we throw explicitly.
throw;
}
#endif
}
}
private static void ThrowMultipleCtorsMarkedWithAttributeException()
{
throw new InvalidOperationException($"Multiple constructors were marked with {nameof(ActivatorUtilitiesConstructorAttribute)}.");
}
private static void ThrowMarkedCtorDoesNotTakeAllProvidedArguments()
{
throw new InvalidOperationException($"Constructor marked with {nameof(ActivatorUtilitiesConstructorAttribute)} does not accept all given argument types.");
}
}
}

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