ValidateOnStart calls configure options twice

[mshann03]

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.

[mshann03]

Sorry, I can't transfer this discussion to the aspnetcore repo, so I'll just mark this as answered and copy to there. Apologies.