44 lines
2.7 KiB
Markdown
44 lines
2.7 KiB
Markdown
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The preferred way to read related configuration values is using the [options pattern](xref:fundamentals/configuration/options). For example, to read the following configuration values:
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```json
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"Position": {
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"Title": "Editor",
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"Name": "Joe Smith"
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}
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```
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Create the following `PositionOptions` class:
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[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Options/PositionOptions.cs?name=snippet)]
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An options class:
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* Must be non-abstract with a public parameterless constructor.
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* All public read-write properties of the type are bound.
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* Fields are ***not*** bound. In the preceding code, `Position` is not bound. The `Position` property is used so the string `"Position"` doesn't need to be hard coded in the app when binding the class to a configuration provider.
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The following code:
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* Calls [ConfigurationBinder.Bind](xref:Microsoft.Extensions.Configuration.ConfigurationBinder.Bind*) to bind the `PositionOptions` class to the `Position` section.
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* Displays the `Position` configuration data.
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[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Pages/Test22.cshtml.cs?name=snippet)]
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In the preceding code, by default, changes to the JSON configuration file after the app has started are read.
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[`ConfigurationBinder.Get<T>`](xref:Microsoft.Extensions.Configuration.ConfigurationBinder.Get*) binds and returns the specified type. `ConfigurationBinder.Get<T>` may be more convenient than using `ConfigurationBinder.Bind`. The following code shows how to use `ConfigurationBinder.Get<T>` with the `PositionOptions` class:
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[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Pages/Test21.cshtml.cs?name=snippet)]
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In the preceding code, by default, changes to the JSON configuration file after the app has started are read.
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An alternative approach when using the ***options pattern*** is to bind the `Position` section and add it to the [dependency injection service container](xref:fundamentals/dependency-injection). In the following code, `PositionOptions` is added to the service container with <xref:Microsoft.Extensions.DependencyInjection.OptionsConfigurationServiceCollectionExtensions.Configure*> and bound to configuration:
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[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Startup.cs?name=snippet)]
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Using the preceding code, the following code reads the position options:
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[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Pages/Test2.cshtml.cs?name=snippet)]
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In the preceding code, changes to the JSON configuration file after the app has started are ***not*** read. To read changes after the app has started, use [IOptionsSnapshot](xref:fundamentals/configuration/options#ios).
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