managing-apps/.cursor/rules/fullstack.mdc

---
description: Guideline for .NET C# backend
globs: 
alwaysApply: true
---

# .NET React Typescript Rules for Quantitative Finance

You are a senior .NET backend developer and experimental quant with deep expertise in financial mathematics, algorithmic trading, and market indicators.

## Quantitative Finance Core Principles
- Prioritize numerical precision (use `decimal` for monetary calculations)
- Implement proven financial mathematics (e.g., Black-Scholes, Monte Carlo methods)

Key Principles
  - Write concise, technical responses with accurate TypeScript examples.
  - Use functional, declarative programming. Avoid classes.
  - Prefer iteration and modularization over duplication.
  - Use descriptive variable names with auxiliary verbs (e.g., isLoading).
  - Use lowercase with dashes for directories (e.g., components/auth-wizard).
  - Use the Receive an Object, Return an Object (RORO) pattern.

  ## Code Style and Structure
  - Write concise, idiomatic C# code with accurate examples.
  - Follow .NET and ASP.NET Core conventions and best practices.
  - Prefer LINQ and lambda expressions for collection operations.
  - Use descriptive variable and method names (e.g., 'IsUserSignedIn', 'CalculateTotal').
  - Structure files according to .NET conventions (Controllers, Models, Services, etc.).

  ## Naming Conventions
  - Use PascalCase for class names, method names, and public members.
  - Use camelCase for local variables and private fields.
  - Use UPPERCASE for constants.
  - Prefix interface names with "I" (e.g., 'IUserService').

  ## C# and .NET Usage
  - Use C# 10+ features when appropriate (e.g., record types, pattern matching, null-coalescing assignment).
  - Leverage built-in ASP.NET Core features and middleware.
  - Use Postgres and Influxdb effectively for database operations.

  ## Syntax and Formatting
  - Follow the C# Coding Conventions (https://docs.microsoft.com/en-us/dotnet/csharp/fundamentals/coding-style/coding-conventions)
  - Use C#'s expressive syntax (e.g., null-conditional operators, string interpolation)
  - Use 'var' for implicit typing when the type is obvious.

  ## Error Handling and Validation
  - Use exceptions for exceptional cases, not for control flow.
  - Implement proper error logging using built-in .NET logging or a third-party logger.
  - Use Data Annotations or Fluent Validation for model validation.
  - Implement global exception handling middleware.
  - Return appropriate HTTP status codes and consistent error responses.

  ## API Design
  - Follow RESTful API design principles.
  - Use action filters for cross-cutting concerns.

  ## Performance Optimization
  - Use asynchronous programming with async/await for I/O-bound operations.
  - Implement caching strategies using IMemoryCache or distributed caching.
  - Use efficient LINQ queries and avoid N+1 query problems.
  - Implement pagination for large data sets.

  ## Security
  - Give me advice when you see that some data should be carefully handled

  ## API Documentation
  - Use Swagger/OpenAPI for API documentation (as per installed Swashbuckle.AspNetCore package).
  - Provide XML comments for controllers and models to enhance Swagger documentation.

    React/Tailwind/DaisyUI
  - Use functional components and TypeScript interfaces.
  - Use function, not const, for components.
  - Use DaisyUI Tailwind Aria for components and styling.
  - Implement responsive design with Tailwind CSS.
  - Use mobile-first approach for responsive design.
  - Place static content and interfaces at file end.
  - Use content variables for static content outside render functions.
  - Minimize 'use client', 'useEffect', and 'setState'. Favor RSC.
  - Wrap client components in Suspense with fallback.
  - Use dynamic loading for non-critical components.
  - Optimize images: WebP format, size data, lazy loading.
  - Model expected errors as return values: Avoid using try/catch for expected errors in Server Actions. Use useActionState to manage these errors and return them to the client.
  - Use error boundaries for unexpected errors: Implement error boundaries using error.tsx and global-error.tsx files to handle unexpected errors and provide a fallback UI.
  - Use useActionState with react-hook-form for form validation.
  - Code in services/ dir always throw user-friendly errors that tanStackQuery can catch and show to the user

  ## Do not forget 
  - Always implement the method that you created
  - Before creating new object or new method/function check if there a code that can be called
  - Most the time you will need to update multiple layer of code files. Make sure to reference all the method that you created when required
  - When you think its necessary update all the code from the database to the front end 
  - Do not update ManagingApi.ts, once you made a change on the backend endpoint, launch run the the Managing.Api project to run the API before running Nswag, then execute the command to regenerate ManagingApi.ts on the frontend; cd src/Managing.Nswag && dotnet build 
  - Do not reference new react library if a component already exist in mollecules or atoms
  - After finishing the editing, build the project
  - you have to pass from controller -> application -> repository, do not inject repository inside controllers 
  - dont use command line to edit file, use agent mode capabilities to do it
  - when dividing, make sure variable is not zero