How to turn on CircuitOptions.DetailedErrors?

Question

I'm getting this message in the console when running a server-side Blazor app:

Error: There was an unhandled exception on the current circuit, so this circuit will be terminated. For more details turn on detailed exceptions in 'CircuitOptions.DetailedErrors'

I've had a look at the Blazor error handling documentation, but I can't work out how to actually turn on the detailed errors mentioned in that message?

Answer 1

More digging on this revealed that there are both non-Blazor specific .NET Core ways to turn on Detailed Errors, and also a Blazor specific approach:

The general .NET Core way to turn on Detailed Errors:

There are a number of ways to get the detailed errors as discussed in the .NET Core documentation, but I ended up using the Detailed Errors setting:

WebHost.CreateDefaultBuilder(args).UseSetting(WebHostDefaults.DetailedErrorsKey, "true")

And the Development Environment setting:

WebHost.CreateDefaultBuilder(args).UseEnvironment(Environments.Development)

Both of those are used in Program.cs:

If you are using the older (and eventually to be deprecated IWebHostBuilder approach) that looks like this:

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .UseSetting(WebHostDefaults.DetailedErrorsKey, "true")
        //.UseEnvironment(EnvironmentName.Development)
        .UseStartup<Startup>();

And if you're using the newer IHostBuilder approach that was introduced with Core 2.1 that looks like this:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder
                .UseStartup<Startup>()
                .UseSetting(WebHostDefaults.DetailedErrorsKey, "true")
                //.UseEnvironment(EnvironmentName.Development);
        });

Once I set that I got more details about my misfiring Blazor code.

A Blazor specific approach:

An alternative approach for turning on detailed errors can also be found in this answer, which includes this code:

services.AddServerSideBlazor().AddCircuitOptions(options => {  options.DetailedErrors = true; });

This approach can then be expanded to include a check for whether the code is being run in the development environment

services.AddServerSideBlazor().AddCircuitOptions(o =>
{
    //only add details when debugging
    o.DetailedErrors = _env.IsDevelopment();
});

as highlighted by @Eonasdan's answer below

Answer 2

A better way to add detailed errors is to check your environment first. In Startup.cs add IWebHostEnvironment env to your constructor.

Then you can do this:

services.AddServerSideBlazor().AddCircuitOptions(o =>
{
    if (_env.IsDevelopment()) //only add details when debugging
    {
        o.DetailedErrors = true;
    }
});

Answer 3

MUCH EASIER

And it does not introduce a possible security issue.

Microsoft recommends adding the following to the appsettings.development.json file as it does not add code to the application that can become a security risk.

It also provides detailed error logging for SignalR.

src: Handle errors in ASP.NET Core Blazor apps: Detailed circuit errors

{
  "DetailedErrors": true, // turns on CircuitOptions.DetailedErrors
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information",
      "Microsoft.AspNetCore.SignalR": "Debug"  // turns on SignalR debugging
    }
  }
}

Answer 4

For me it was slightly different

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseSetting(WebHostDefaults.DetailedErrorsKey, "true");
            webBuilder.UseStartup<Startup>();
        });

Answer 5

For .NET Core 6 you can use WebApplicationBuilder.

var builder = WebApplication.CreateBuilder(args);
if (builder.Environment.IsDevelopment())
{
    builder.Services.AddServerSideBlazor().AddCircuitOptions(x => x.DetailedErrors = true);
}
else
{
    builder.Services.AddServerSideBlazor();
}