Getting Started

This walkthrough wires up MRX-flavored validation errors on an ASP.NET Core API and consumes them from a Blazor client.

Server: configure model binding validation

Install the package:

dotnet add package MRX.Core

Then, in Program.cs, opt in to the MRX validation pipeline:

builder.Services.ConfigureMrxModelBindingValidation();

This replaces the default IObjectModelValidator with one that re-keys validation errors as camelCase JSON paths and returns them as CodedError instances under an errors extension on the ProblemDetails response, instead of the default free-text ModelState errors.

You can customize the casing applied to error keys:

builder.Services.ConfigureMrxModelBindingValidation(options =>
{
    options.ErrorKeyNamingPolicy = JsonNamingPolicy.SnakeCaseLower;
});

If an endpoint accepts request data from more than one binding source and those sources can have colliding field names (e.g. a route parameter and a body property both named id), read Disambiguation before deciding whether to opt that endpoint in to key disambiguation.

Client: auto-wire errors into a Blazor form

Install the package:

dotnet add package MRX.UI.ErrorsAutoWiring

Register the services, optionally configuring the underlying HttpClient (e.g. its BaseAddress):

builder.Services.AddErrorsAutoWiringServices(client =>
{
    client.BaseAddress = new Uri("https://api.example.com");
});

In your component, bind the EditContext's model to a DataBindingSources instance holding the models used for the request body and query string, then send requests through ProblemDetailsHttpClient:

DataBindingSources sources = new() { Body = myRequestBody, Query = myRequestQuery };
EditContext editContext = new(sources);

HttpResponseMessage response = await problemDetailsHttpClient.SendContextAwareAsync(
    editContext,
    new HttpRequestMessage(HttpMethod.Post, "/orders") { Content = JsonContent.Create(myRequestBody) },
    cancellationToken);

SendContextAwareAsync maps any errors extension in the response back onto editContext's ValidationMessageStore, matching each server-provided JSON path to the corresponding field in myRequestBody or myRequestQuery — no manual key-to-field mapping required, and no changes needed in your Razor markup: <ValidationMessage For="..."/> keeps working as-is.

Continue to Concepts for a deeper look at how error keys are resolved.

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