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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;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Diagnostics.Metrics;
using Microsoft.Extensions.Hosting.Internal;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.EventLog;
namespace Microsoft.Extensions.Hosting
{
/// <summary>
/// Provides extension methods for the <see cref="IHostBuilder"/> from the hosting package.
/// </summary>
public static class HostingHostBuilderExtensions
{
/// <summary>
/// Specify the environment to be used by the host. To avoid the environment being overwritten by a default
/// value, ensure this is called after defaults are configured.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder"/> to configure.</param>
/// <param name="environment">The environment to host the application in.</param>
/// <returns>The <see cref="IHostBuilder"/>.</returns>
public static IHostBuilder UseEnvironment(this IHostBuilder hostBuilder, string environment)
{
return hostBuilder.ConfigureHostConfiguration(configBuilder =>
{
ThrowHelper.ThrowIfNull(environment);
configBuilder.AddInMemoryCollection(new[]
{
new KeyValuePair<string, string?>(HostDefaults.EnvironmentKey, environment)
});
});
}
/// <summary>
/// Specify the content root directory to be used by the host. To avoid the content root directory being
/// overwritten by a default value, ensure this is called after defaults are configured.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder"/> to configure.</param>
/// <param name="contentRoot">Path to root directory of the application.</param>
/// <returns>The <see cref="IHostBuilder"/>.</returns>
public static IHostBuilder UseContentRoot(this IHostBuilder hostBuilder, string contentRoot)
{
return hostBuilder.ConfigureHostConfiguration(configBuilder =>
{
ThrowHelper.ThrowIfNull(contentRoot);
configBuilder.AddInMemoryCollection(new[]
{
new KeyValuePair<string, string?>(HostDefaults.ContentRootKey, contentRoot)
});
});
}
/// <summary>
/// Specify the <see cref="IServiceProvider"/> to be the default one.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder"/> to configure.</param>
/// <param name="configure">The delegate that configures the <see cref="IServiceProvider"/>.</param>
/// <returns>The <see cref="IHostBuilder"/>.</returns>
public static IHostBuilder UseDefaultServiceProvider(this IHostBuilder hostBuilder, Action<ServiceProviderOptions> configure)
=> hostBuilder.UseDefaultServiceProvider((context, options) => configure(options));
/// <summary>
/// Specify the <see cref="IServiceProvider"/> to be the default one.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder"/> to configure.</param>
/// <param name="configure">The delegate that configures the <see cref="IServiceProvider"/>.</param>
/// <returns>The <see cref="IHostBuilder"/>.</returns>
public static IHostBuilder UseDefaultServiceProvider(this IHostBuilder hostBuilder, Action<HostBuilderContext, ServiceProviderOptions> configure)
{
return hostBuilder.UseServiceProviderFactory(context =>
{
var options = new ServiceProviderOptions();
configure(context, options);
return new DefaultServiceProviderFactory(options);
});
}
/// <summary>
/// Adds a delegate for configuring the provided <see cref="ILoggingBuilder"/>. This may be called multiple times.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureLogging">The delegate that configures the <see cref="ILoggingBuilder"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureLogging(this IHostBuilder hostBuilder, Action<HostBuilderContext, ILoggingBuilder> configureLogging)
{
return hostBuilder.ConfigureServices((context, collection) => collection.AddLogging(builder => configureLogging(context, builder)));
}
/// <summary>
/// Adds a delegate for configuring the provided <see cref="ILoggingBuilder"/>. This may be called multiple times.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureLogging">The delegate that configures the <see cref="ILoggingBuilder"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureLogging(this IHostBuilder hostBuilder, Action<ILoggingBuilder> configureLogging)
{
return hostBuilder.ConfigureServices((context, collection) => collection.AddLogging(configureLogging));
}
/// <summary>
/// Adds a delegate for configuring the <see cref="HostOptions"/> of the <see cref="IHost"/>.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureOptions">The delegate for configuring the <see cref="HostOptions"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureHostOptions(this IHostBuilder hostBuilder, Action<HostBuilderContext, HostOptions> configureOptions)
{
return hostBuilder.ConfigureServices(
(context, collection) => collection.Configure<HostOptions>(options => configureOptions(context, options)));
}
/// <summary>
/// Adds a delegate for configuring the <see cref="HostOptions"/> of the <see cref="IHost"/>.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureOptions">The delegate for configuring the <see cref="HostOptions"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureHostOptions(this IHostBuilder hostBuilder, Action<HostOptions> configureOptions)
{
return hostBuilder.ConfigureServices(collection => collection.Configure(configureOptions));
}
/// <summary>
/// Sets up the configuration for the remainder of the build process and application. This can be called multiple times and
/// the results will be additive. The results will be available at <see cref="HostBuilderContext.Configuration"/> for
/// subsequent operations, as well as in <see cref="IHost.Services"/>.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureDelegate">The delegate for configuring the <see cref="IConfigurationBuilder"/> that will be used
/// to construct the <see cref="IConfiguration"/> for the host.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureAppConfiguration(this IHostBuilder hostBuilder, Action<IConfigurationBuilder> configureDelegate)
{
return hostBuilder.ConfigureAppConfiguration((context, builder) => configureDelegate(builder));
}
/// <summary>
/// Adds services to the container. This can be called multiple times and the results will be additive.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureDelegate">The delegate for configuring the <see cref="IServiceCollection"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureServices(this IHostBuilder hostBuilder, Action<IServiceCollection> configureDelegate)
{
return hostBuilder.ConfigureServices((context, collection) => configureDelegate(collection));
}
/// <summary>
/// Enables configuring the instantiated dependency container. This can be called multiple times and
/// the results will be additive.
/// </summary>
/// <typeparam name="TContainerBuilder">The type of builder.</typeparam>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureDelegate">The delegate for configuring the <typeparamref name="TContainerBuilder"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureContainer<TContainerBuilder>(this IHostBuilder hostBuilder, Action<TContainerBuilder> configureDelegate)
{
return hostBuilder.ConfigureContainer<TContainerBuilder>((context, builder) => configureDelegate(builder));
}
/// <summary>
/// Configures an existing <see cref="IHostBuilder"/> instance with pre-configured defaults. This will overwrite
/// previously configured values and is intended to be called before additional configuration calls.
/// </summary>
/// <remarks>
/// The following defaults are applied to the <see cref="IHostBuilder"/>:
/// * set the <see cref="IHostEnvironment.ContentRootPath"/> to the result of <see cref="Directory.GetCurrentDirectory()"/>
/// * load host <see cref="IConfiguration"/> from "DOTNET_" prefixed environment variables
/// * load host <see cref="IConfiguration"/> from supplied command line args
/// * load app <see cref="IConfiguration"/> from 'appsettings.json' and 'appsettings.[<see cref="IHostEnvironment.EnvironmentName"/>].json'
/// * load app <see cref="IConfiguration"/> from User Secrets when <see cref="IHostEnvironment.EnvironmentName"/> is 'Development' using the entry assembly
/// * load app <see cref="IConfiguration"/> from environment variables
/// * load app <see cref="IConfiguration"/> from supplied command line args
/// * configure the <see cref="ILoggerFactory"/> to log to the console, debug, and event source output
/// * enables scope validation on the dependency injection container when <see cref="IHostEnvironment.EnvironmentName"/> is 'Development'
/// </remarks>
/// <param name="builder">The existing builder to configure.</param>
/// <param name="args">The command line args.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureDefaults(this IHostBuilder builder, string[]? args)
{
return builder.ConfigureHostConfiguration(config => ApplyDefaultHostConfiguration(config, args))
.ConfigureAppConfiguration((hostingContext, config) => ApplyDefaultAppConfiguration(hostingContext, config, args))
.ConfigureServices(AddDefaultServices)
.UseServiceProviderFactory(context => new DefaultServiceProviderFactory(CreateDefaultServiceProviderOptions(context)));
}
private static void ApplyDefaultHostConfiguration(IConfigurationBuilder hostConfigBuilder, string[]? args)
{
SetDefaultContentRoot(hostConfigBuilder);
hostConfigBuilder.AddEnvironmentVariables(prefix: "DOTNET_");
AddCommandLineConfig(hostConfigBuilder, args);
}
internal static void SetDefaultContentRoot(IConfigurationBuilder hostConfigBuilder)
{
// If we're running anywhere other than C:\Windows\system32, we default to using the CWD for the ContentRoot.
// However, since many things like Windows services and MSIX installers have C:\Windows\system32 as there CWD which is not likely
// to really be the home for things like appsettings.json, we skip changing the ContentRoot in that case. The non-"default" initial
// value for ContentRoot is AppContext.BaseDirectory (e.g. the executable path) which probably makes more sense than the system32.
// In my testing, both Environment.CurrentDirectory and Environment.SystemDirectory return the path without
// any trailing directory separator characters. I'm not even sure the casing can ever be different from these APIs, but I think it makes sense to
// ignore case for Windows path comparisons given the file system is usually (always?) going to be case insensitive for the system path.
string cwd = Environment.CurrentDirectory;
if (
#if NETFRAMEWORK
Environment.OSVersion.Platform != PlatformID.Win32NT ||
#else
!RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ||
#endif
!string.Equals(cwd, Environment.SystemDirectory, StringComparison.OrdinalIgnoreCase))
{
hostConfigBuilder.AddInMemoryCollection(new[]
{
new KeyValuePair<string, string?>(HostDefaults.ContentRootKey, cwd),
});
}
}
internal static void ApplyDefaultAppConfiguration(HostBuilderContext hostingContext, IConfigurationBuilder appConfigBuilder, string[]? args)
{
IHostEnvironment env = hostingContext.HostingEnvironment;
bool reloadOnChange = GetReloadConfigOnChangeValue(hostingContext);
appConfigBuilder.AddJsonFile("appsettings.json", optional: true, reloadOnChange: reloadOnChange)
.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: reloadOnChange);
if (env.IsDevelopment() && env.ApplicationName is { Length: > 0 })
{
try
{
var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName));
appConfigBuilder.AddUserSecrets(appAssembly, optional: true, reloadOnChange: reloadOnChange);
}
catch (FileNotFoundException)
{
// The assembly cannot be found, so just skip it.
}
}
appConfigBuilder.AddEnvironmentVariables();
AddCommandLineConfig(appConfigBuilder, args);
[UnconditionalSuppressMessage("ReflectionAnalysis", "IL2026:RequiresUnreferencedCode", Justification = "Calling IConfiguration.GetValue is safe when the T is bool.")]
static bool GetReloadConfigOnChangeValue(HostBuilderContext hostingContext) => hostingContext.Configuration.GetValue("hostBuilder:reloadConfigOnChange", defaultValue: true);
}
internal static void AddCommandLineConfig(IConfigurationBuilder configBuilder, string[]? args)
{
if (args is { Length: > 0 })
{
configBuilder.AddCommandLine(args);
}
}
internal static void AddDefaultServices(HostBuilderContext hostingContext, IServiceCollection services)
{
services.AddLogging(logging =>
{
bool isWindows =
#if NET
OperatingSystem.IsWindows();
#elif NETFRAMEWORK
Environment.OSVersion.Platform == PlatformID.Win32NT;
#else
RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
#endif
// IMPORTANT: This needs to be added *before* configuration is loaded, this lets
// the defaults be overridden by the configuration.
if (isWindows)
{
// Default the EventLogLoggerProvider to warning or above
logging.AddFilter<EventLogLoggerProvider>(level => level >= LogLevel.Warning);
}
logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
#if NET
if (!OperatingSystem.IsBrowser())
#endif
{
logging.AddConsole();
}
logging.AddDebug();
logging.AddEventSourceLogger();
if (isWindows)
{
// Add the EventLogLoggerProvider on windows machines
logging.AddEventLog();
}
logging.Configure(options =>
{
options.ActivityTrackingOptions =
ActivityTrackingOptions.SpanId |
ActivityTrackingOptions.TraceId |
ActivityTrackingOptions.ParentId;
});
});
services.AddMetrics(metrics =>
{
metrics.AddConfiguration(hostingContext.Configuration.GetSection("Metrics"));
});
}
internal static ServiceProviderOptions CreateDefaultServiceProviderOptions(HostBuilderContext context)
{
bool isDevelopment = context.HostingEnvironment.IsDevelopment();
return new ServiceProviderOptions
{
ValidateScopes = isDevelopment,
ValidateOnBuild = isDevelopment,
};
}
/// <summary>
/// Listens for Ctrl+C or SIGTERM and calls <see cref="IHostApplicationLifetime.StopApplication"/> to start the shutdown process.
/// This will unblock extensions like RunAsync and WaitForShutdownAsync.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
[UnsupportedOSPlatform("android")]
[UnsupportedOSPlatform("browser")]
[UnsupportedOSPlatform("ios")]
[UnsupportedOSPlatform("tvos")]
public static IHostBuilder UseConsoleLifetime(this IHostBuilder hostBuilder)
{
return hostBuilder.ConfigureServices(collection => collection.AddSingleton<IHostLifetime, ConsoleLifetime>());
}
/// <summary>
/// Listens for Ctrl+C or SIGTERM and calls <see cref="IHostApplicationLifetime.StopApplication"/> to start the shutdown process.
/// This will unblock extensions like RunAsync and WaitForShutdownAsync.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureOptions">The delegate for configuring the <see cref="ConsoleLifetime"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
[UnsupportedOSPlatform("android")]
[UnsupportedOSPlatform("browser")]
[UnsupportedOSPlatform("ios")]
[UnsupportedOSPlatform("tvos")]
public static IHostBuilder UseConsoleLifetime(this IHostBuilder hostBuilder, Action<ConsoleLifetimeOptions> configureOptions)
{
return hostBuilder.ConfigureServices(collection =>
{
collection.AddSingleton<IHostLifetime, ConsoleLifetime>();
collection.Configure(configureOptions);
});
}
/// <summary>
/// Enables console support, builds and starts the host, and waits for Ctrl+C or SIGTERM to shut down.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="cancellationToken">A <see cref="CancellationToken"/> that can be used to cancel the console.</param>
/// <returns>A <see cref="Task"/> that only completes when the token is triggered or shutdown is triggered.</returns>
[UnsupportedOSPlatform("android")]
[UnsupportedOSPlatform("browser")]
[UnsupportedOSPlatform("ios")]
[UnsupportedOSPlatform("tvos")]
public static Task RunConsoleAsync(this IHostBuilder hostBuilder, CancellationToken cancellationToken = default)
{
return hostBuilder.UseConsoleLifetime().Build().RunAsync(cancellationToken);
}
/// <summary>
/// Enables console support, builds and starts the host, and waits for Ctrl+C or SIGTERM to shut down.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureOptions">The delegate for configuring the <see cref="ConsoleLifetime"/>.</param>
/// <param name="cancellationToken">A <see cref="CancellationToken"/> that can be used to cancel the console.</param>
/// <returns>A <see cref="Task"/> that only completes when the token is triggered or shutdown is triggered.</returns>
[UnsupportedOSPlatform("android")]
[UnsupportedOSPlatform("browser")]
[UnsupportedOSPlatform("ios")]
[UnsupportedOSPlatform("tvos")]
public static Task RunConsoleAsync(this IHostBuilder hostBuilder, Action<ConsoleLifetimeOptions> configureOptions, CancellationToken cancellationToken = default)
{
return hostBuilder.UseConsoleLifetime(configureOptions).Build().RunAsync(cancellationToken);
}
/// <summary>
/// Adds a delegate for configuring the provided <see cref="IMetricsBuilder"/>. This may be called multiple times.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureMetrics">The delegate that configures the <see cref="IMetricsBuilder"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureMetrics(this IHostBuilder hostBuilder, Action<IMetricsBuilder> configureMetrics)
{
return hostBuilder.ConfigureServices((context, collection) => collection.AddMetrics(configureMetrics));
}
/// <summary>
/// Adds a delegate for configuring the provided <see cref="IMetricsBuilder"/>. This may be called multiple times.
/// </summary>
/// <param name="hostBuilder">The <see cref="IHostBuilder" /> to configure.</param>
/// <param name="configureMetrics">The delegate that configures the <see cref="IMetricsBuilder"/>.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public static IHostBuilder ConfigureMetrics(this IHostBuilder hostBuilder, Action<HostBuilderContext, IMetricsBuilder> configureMetrics)
{
return hostBuilder.ConfigureServices((context, collection) => collection.AddMetrics(builder => configureMetrics(context, builder)));
}
}
}
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