Mjolnir.Extensions.Exceptions 10.0.6

Mjolnir.Extensions.Exceptions

Simple MCP server compatible exceptions, HTTP request validators, and global handlers for ASP.NET Core.

Overview

Mjolnir.Extensions.Exceptions provides a standardized way to handle exceptions and validation in ASP.NET Core applications. It includes base exception classes, global exception handlers that convert exceptions to ProblemDetails, and a fluent validation rule system for Minimal APIs.

Key Features:

• MjolnirException: A base exception class with extensive static helper methods for common validation checks (e.g., ThrowIfNull, ThrowIfZero, ThrowIfNegative).
• ValidationException: A specialized exception for accumulating and reporting multiple validation errors.
• Global Handlers: Middleware handlers for MjolnirException and ValidationException that automatically produce standardized ProblemDetails responses.
• RuleSet & Minimal API Integration: A fluent API for defining custom validation rules on endpoints.

Requirements

• Runtime: .NET 10.0+
• Language: C# 14.0+
• Dependencies:
  • Microsoft.AspNetCore.OpenApi (10.0.5)
  • Microsoft.Extensions.DependencyInjection.Abstractions (10.0.5)
  • ModelContextProtocol.Core (1.1.0)

Setup

Installation

Install the package via NuGet:

dotnet add package Mjolnir.Extensions.Exceptions

Configuration

Register the exception handlers in your Program.cs:

using Mjolnir.Extensions.Exceptions.DependencyInjection;

var builder = WebApplication.CreateBuilder(args);

// Add Mjolnir exception handlers
builder.Services.AddMjolnirExceptionsHandler();

var app = builder.Build();

// Use the exception handler middleware
app.UseMjolnirExceptionHandler();

app.Run();

Usage

MjolnirException

Use the static helper methods to perform validation and throw exceptions with specific HTTP status codes:

MjolnirException.ThrowIfNull(user, "User not found", HttpStatusCode.NotFound);
MjolnirException.ThrowIfNegative(price, "Price cannot be negative");

ValidationException

Accumulate multiple validation errors:

var ex = new ValidationException();

if (string.IsNullOrEmpty(request.Name))
    ex.WithError(nameof(request.Name), "Name is required");

if (request.Age < 18)
    ex.WithError(nameof(request.Age), "Must be at least 18");

ex.ThrowIfHasError();

Minimal API RuleSets

Define custom validation rules for your endpoints:

app.MapPost("/users", (User user) => Results.Ok(user))
   .AddRules<User>(rules =>
   {
       rules.AddRule(u => !string.IsNullOrEmpty(u.Username), "Username is required", nameof(User.Username));
       rules.AddRule(async u => await IsUsernameUnique(u.Username), "Username already taken", nameof(User.Username));
   });

Project Structure

Mjolnir.Extensions.Exceptions/
├── DependencyInjection/
│   └── Di.cs                       # DI registration extensions
├── Handlers/
│   ├── MjolnirExceptionHandler.cs   # Global handler for MjolnirException
│   └── ValidationExceptionHandler.cs # Global handler for ValidationException
├── Rules/
│   ├── RuleSet.cs                   # Fluent validation rule builder
│   └── RulesExtensions.cs           # Endpoint filter extensions for Rules
├── MjolnirException.cs              # Base exception with helper methods
├── ValidationException.cs           # Multi-error validation exception
└── Mjolnir.Extensions.Exceptions.csproj

License

This project is licensed under the LICENSE file in the root of the repository.