https://ingomoney.com/developer-blog/net-core-options-pattern-for-live-reload-settings/

Hello,

I've got a scenario where I'm using OptionsBuilderExtensions.ValidateOnStart to validate some settings to fail fast if there are any values missing etc.

I've wired in an IValidateOptions<> implementation to do the validation, and I have an IConfigureOptions<> implementation to change some of the settings on load.

The issue I'm experiencing is both the configure and validate implementations get called twice, and if I change any of the setting values in the first call to configure, it resets on the second call. Is this expected? I would have thought he validate and configure would run once, both on startup.

Here is a cutdown sample that illustrates my point:

Simple program.cs setup:

using Microsoft.Extensions.Options;
using OptionsValidationExample;
var builder = WebApplication.CreateBuilder(args);
builder
 .Services
 .AddOptions<GreetingSettings>()
 .Configure(settings => settings.Name = "Initial Name")
 .ValidateOnStart();
builder.Services.AddSingleton<IValidateOptions<GreetingSettings>, SettingsValidateOptions>();
builder.Services.AddSingleton<IConfigureOptions<GreetingSettings>, SettingsConfigureOptions>();
 
var app = builder.Build();
app.MapGet("/", (IOptions<GreetingSettings> settings) =>
{
 return $"Hello {settings.Value.Name}!";
});
app.Run();

And my GreetingSettings.cs file complete with validateoptions and configureoptions implementations:

using Microsoft.Extensions.Options;
using System.Diagnostics;
namespace OptionsValidationExample;
public class GreetingSettings
{
 public string Name { get; set; } = null!;
}
public class SettingsConfigureOptions : IConfigureOptions<GreetingSettings>
{
 public void Configure(GreetingSettings options)
 {
 // This method gets called twice due to ValidateOnStartup for the settings.
 Debugger.Break();
 // The second time it should come through as "Changed Name".
 Debug.Assert(options.Name == "Initial Name");
 options.Name = "Changed Name";
 }
}
public class SettingsValidateOptions : IValidateOptions<GreetingSettings>
{
 public ValidateOptionsResult Validate(string name, GreetingSettings options)
 {
 // This method gets called twice: once for ValidateOnStartup and once for first usage.
 Debugger.Break();
 return ValidateOptionsResult.Success;
 }
}

Any suggestions on how to fix this?

Many thanks in advance,

Mark.