.net Core3.0 how to configure Configuration

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Prepare for

There have been great changes in the configuration of .NET core and .NET projects, with richer support such as command line, environment variables, in-memory .NET objects, settings files, and so on. Net projects we often put configuration information in webConfig or appConfig. Configure the relevant source code https://github.com/aspnet/Extensions; if you open the source code project, if you encounter the following error, do not encounter a direct skip.

Error prompt: error: The project file cannot be opened by the project system, because it is missing some critical imports or the referenced SDK cannot be found. Detailed Information:

Solution: check whether the locally installed sdk is consistent with the version developed in global.json: then modify it

To start a new Asp.net Core web application, the appsettings.json is created by default; when the application starts the build host, the CreateDefaultBuilder method is called, and the appsettings.json is loaded by default. The code is as follows: public static IHostBuilder CreateDefaultBuilder (string [] args) {var builder = new HostBuilder ()

Builder.UseContentRoot (Directory.GetCurrentDirectory ()); builder.ConfigureHostConfiguration (config = > {config.AddEnvironmentVariables (prefix: "DOTNET_"); if (args! = null) {config.AddCommandLine (args);}})

Builder.ConfigureAppConfiguration ((hostingContext, config) = > {var env = hostingContext.HostingEnvironment

Config.AddJsonFile ("appsettings.json", optional: true, reloadOnChange: true) .AddJsonFile ($"appsettings. {env.EnvironmentName} .json", optional: true, reloadOnChange: true)

If (env.IsDevelopment () & &! string.IsNullOrEmpty (env.ApplicationName)) {var appAssembly = Assembly.Load (new AssemblyName (env.ApplicationName)); if (appAssembly! = null) {config.AddUserSecrets (appAssembly, optional: true) }} use GetValue,GetSection,GetChildren to read appsettings.json key-value pairs. We open the appsettings.json file:

When you read the file into the configuration, a unique hierarchical key is created to save the configuration values:

Logging:LogLevel:Default

Logging:LogLevel:System

Logging:LogLevel:Microsoft

Logging:LogLevel:Microsoft.Hosting.Lifetime

AllowedHosts

Var jsonValue = $"AllowedHosts: {_ config [" AllowedHosts "]}" + "\ r\ n"; jsonValue + = "Logging:LogLevel:Default:" + _ config.GetValue ("Logging:LogLevel:Default") + "\ r\ n"

/ / GetSection returns IConfigurationSection If it does not match to return null / / jsonValue + = "- -" + _ config.GetSection ("Logging:LogLevel:System"); jsonValue + = "Logging:LogLevel:System:" + _ config.GetSection ("Logging:LogLevel:System"). Value+ "\ r\ n\ n"; var logSection = _ config.GetSection ("Logging:LogLevel"); var configurationSections = logSection.GetChildren () Foreach (var sections in configurationSections) {jsonValue + = $"{sections.Path}: {sections.Value}"; jsonValue + = "\ r\ n";} jsonValue + = "\ r\ n"

Output:

Configure the specified json file to bind to the class create a new json file-AAAppSettings.json {"AA": {"RabbitMqHostUrl": "rabbitmq://localhost:5672", "RabbitMqHostName": "localhost", "RabbitMqUserName": "admin", "RabbitMqPassword": "123"}}

Use the ConfigureAppConfiguration method to configure the specified json file public static IHostBuilder CreateHostBuilder (string [] args) = > Host.CreateDefaultBuilder (args) .ConfigreAppConfiguration ((hostingContext, config) = > {config.SetBasePath (Directory.GetCurrentDirectory ()); config.AddJsonFile ("AAAppSettings.json", optional: true, reloadOnChange: true);})

Use the bind method to bind to a newly created class, such as:

Public partial class AAConfig {public string RabbitMqHostUrl {get; set;} public string RabbitMqHostName {get; set;} public string RabbitMqUserName {get; set;} public string RabbitMqPassword {get; set;}} var aaConfig = new AAConfig (); _ config.GetSection ("AA") .Bind (aaConfig); jsonValue + = aaConfig.RabbitMqHostUrl + "\ r\ n"; jsonValue + = aaConfig.RabbitMqHostName + "\ r\ n"; jsonValue + = aaConfig.RabbitMqUserName + "\ r\ n" JsonValue + = aaConfig.RabbitMqPassword + "\ r\ n"; return jsonValue

Run the output:

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