手动触发IOptionsMonitor<> .OnChange

问题描述

在ASP.NET Core 2.1中，我使用IOptionsMonitor<>进行设置，以便在更改appSettings.json文件时可以成功获取事件.这样就可以了.

In ASP.NET Core 2.1, I use IOptionsMonitor<> and have it set up so I can successfully get events for when I change the appSettings.json file. So this is working.

我现在要做的是通过代码手动更改选项中的某些值，并触发所有监视器.这可能吗?

What I want to do now is to manually change some values in my options, through code, and have that trigger all my monitors. Is this possible?

推荐答案

对于IOptionsMonitor<Locations>，它仅更改内存中的值，而没有保存回appsettings.json.要解决此问题，您将需要实现自己的方法以将更改保存回appsettings.json.

For IOptionsMonitor<Locations>, it only changes the value in memory and did not save back to appsettings.json. For a workaround, you will need to implement your own method to save the changes back to appsettings.json.

• 定义从IOptions

public interface IWritableOptions<out T> : IOptions<T> where T : class, new()
{
     void Update(Action<T> applyChanges);
}

实现自己的WritableOptions

public class WritableOptions<T> : IWritableOptions<T> where T : class, new()
{
private readonly IHostingEnvironment _environment;
private readonly IOptionsMonitor<T> _options;
private readonly IConfigurationRoot _configuration;
private readonly string _section;
private readonly string _file;

public WritableOptions(
    IHostingEnvironment environment,
    IOptionsMonitor<T> options,
    IConfigurationRoot configuration,
    string section,
    string file)
{
    _environment = environment;
    _options = options;
    _configuration = configuration;
    _section = section;
    _file = file;
}

public T Value => _options.CurrentValue;
public T Get(string name) => _options.Get(name);

public void Update(Action<T> applyChanges)
{
    var fileProvider = _environment.ContentRootFileProvider;
    var fileInfo = fileProvider.GetFileInfo(_file);
    var physicalPath = fileInfo.PhysicalPath;

    var jObject = JsonConvert.DeserializeObject<JObject>(File.ReadAllText(physicalPath));
    var sectionObject = jObject.TryGetValue(_section, out JToken section) ?
        JsonConvert.DeserializeObject<T>(section.ToString()) : (Value ?? new T());

    applyChanges(sectionObject);

    jObject[_section] = JObject.Parse(JsonConvert.SerializeObject(sectionObject));
    File.WriteAllText(physicalPath, JsonConvert.SerializeObject(jObject, Formatting.Indented));
    _configuration.Reload();
}
}

配置IWritableOptions<T>

public static class ServiceCollectionExtensions
{
public static void ConfigureWritable<T>(
    this IServiceCollection services,
    IConfigurationSection section,
    string file = "appsettings.json") where T : class, new()
{
    services.Configure<T>(section);
    services.AddTransient<IWritableOptions<T>>(provider =>
    {
        var configuration = (IConfigurationRoot)provider.GetService<IConfiguration>();
        var environment = provider.GetService<IHostingEnvironment>();
        var options = provider.GetService<IOptionsMonitor<T>>();
        return new WritableOptions<T>(environment, options, configuration, section.Key, file);
    });
}
}

在Startup

        services.ConfigureWritable<Locations>(Configuration.GetSection("Locations"));

使用

Use

public class OptionsController : Controller
{
private readonly IWritableOptions<Locations> _writableLocations;
public OptionsController(IWritableOptions<Locations> writableLocations)
{
    _writableLocations = writableLocations;
}

public IActionResult Change(string value)
{
    _writableLocations.Update(opt => {
        opt.Name = value;
    });
    return Ok("OK");
}
}

它将触发IOptionsMonitor<>.OnChange

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