.NET developer cheat sheet (Blazor)

1. 1C# syntax you use every dayThe parts of modern C# that show up in every ASP.NET Core codebase. C# 14 ships with .NET 10; most of what is here works from C# 9 onwards.9 concepts

   1. 1Value types and reference typesA struct (int, decimal, DateTime, your own structs) is copied when you assign or pass it.
   2. 2RecordsA record is a type built for data: the compiler writes value equality, a readable ToString and, with positional syntax, an immutable constructor and properties.
   3. 3Pattern matching and switch expressionsPatterns test the shape of a value: its type, a constant, a range or its properties.
   4. 4Nullable reference typesWith <Nullable>enable</Nullable> (on in every new template) string means never null and string? means may be null.
   5. 5Primary constructorsSince C# 12, a class can declare constructor parameters next to its name.
   6. 6Collection expressionsSince C# 12, [a, b, c] creates an array, List, Span or other collection, chosen by the target type.
   7. 7Generics and constraintsGenerics let a class or method work with any type while staying type-safe: List<Order> only holds orders.
   8. 8Extension methods and extension membersAn extension method adds a method to a type you do not own, through a static class and a this parameter.
   9. 9Exceptions, using and finallyCode throws an exception for a situation it cannot handle; the nearest matching catch up the call stack handles it.

   9 in this chapterOpen this chapter
2. 2LINQLanguage Integrated Query: one set of methods for filtering, shaping and grouping data, in memory or translated to SQL by EF Core.6 concepts

   1. 1Where, Select and OrderByLINQ methods chain together: Where filters, Select shapes each item into something new, OrderBy and ThenBy sort, Take and Skip page.
   2. 2Deferred executionA LINQ query does nothing when you write it.
   3. 3GroupBy and aggregatesGroupBy buckets items by a key; Sum, Count, Average, Min and Max reduce a sequence or each group to one value.
   4. 4First, Single and the OrDefault versionsFirst takes the first match and throws if there is none.
   5. 5IEnumerable vs IQueryableIEnumerable runs LINQ in memory with C# delegates.
   6. 6Choosing a collectionList<T> keeps order and allows duplicates.

   6 in this chapterOpen this chapter
3. async, await and TasksHow .NET waits for databases and HTTP calls without blocking threads. ASP.NET Core is async from top to bottom, so these rules apply to every endpoint.6 conceptsOpens with credits
4. The dotnet CLI and the platformWhat you install, how projects are created and built, and which .NET version to target. Everything here works the same on Windows, macOS and Linux.7 conceptsOpens with credits
5. Dependency injection and configurationHow ASP.NET Core creates your services and hands them their settings. Lifetimes are the part that causes real production bugs.7 conceptsOpens with credits
6. Middleware pipeline, routing and endpointsEvery request passes through a chain of middleware before it reaches an endpoint. Order matters, and most "it works locally but not in production" bugs start here.8 conceptsOpens with credits
7. EF Core commands and pitfallsEntity Framework Core maps C# classes to tables and LINQ to SQL. It is fast to start with and easy to make slow, so the pitfalls matter as much as the commands.10 conceptsOpens with credits
8. Auth, security and the front endWho the caller is, what they may do, and how a browser front end or another client talks to your API safely.6 conceptsOpens with credits
9. Testing, shipping and background workHow .NET teams prove code works, package it, deploy it to Azure and run work outside the request.10 conceptsOpens with credits
10. Production checklistTen things a production ASP.NET Core API needs, each with the Program.cs code to add it. The .NET version each feature arrived in is noted; all of it works on .NET 10.10 conceptsOpens with credits
11. 11Glossary, A to ZEvery concept in the sheet and the smaller terms it uses, in one list.138 terms

C#, ASP.NET Core, EF Core, production-ready APIs.