.NET Core 6 minimal API with OpenApi - validate request against OpenApi schema

Question

I'm working on a minimal API in .NET Core 6 with OpenApi support.

I have a Resolution model defined like this:

using System.ComponentModel.DataAnnotations;

public struct Resolution
{
    [Required, Range(1, 800)]
    public int W { get; set; }

    [Required, Range(1, 600)]
    public int H { get; set; }
}

Then I have a POST endpoint definition like this:

app.MapPut("/resolutions", (Resolution res) =>
{
    //Some logic here
    return Results.Ok(new { Message = "Resource updated successfully" });
})
.Produces(200)
.Produces(404)
.WithName("PutResolution");

Case 1. I send a PUT request (out of range value fore w):

"resolution": {
    "w": 1024,
    "h": 400
}

Result: 200 OK.

Case 2: I send a PUT request (wrong data type for w):

"resolution": {
    "w": "xl",
    "h": 400
}

Result: 400 JsonException

Issue:

relying on JsonException on deserialization. Preferably a schema validation error should be returned to consumer.

Questions:

What is the best practice to handle validation in this case?
Is there a way to validate incoming request against the OpenApi contract, which in this case, is generated on the fly? In this case both wrong data type and value out of range issues would be validated before entering the route handler.

Guru Stron · Accepted Answer · 2023-05-25 13:32:16Z

1

As mentioned in this document,There's no built-in support for validation in .NET 6 Minimal API.

If you do want it, you could try third party solutions such as this blog.

edited May 25, 2023 at 13:32

Guru Stron

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answered May 24, 2023 at 2:35

Ruikai Feng

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Comments

Fuczak · Accepted Answer · 2023-05-29 16:19:16Z

0

Solved using NuGet package: MiniValidation (https://www.nuget.org/packages/MiniValidation/) as suggested by @Ruikai. It would still fail on deserialization I can compromise on this.

Usage:

static async Task<IResult> PutImage(string id, Image image)
{
  if(!MiniValidator.TryValidate(image, out var errors))
  {
    return Results.ValidationProblem(errors);
  }
}

answered May 29, 2023 at 16:19

Fuczak

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