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Coding Guidelines for C# v10 Cheat Sheet ![logo](assets/images/logo.png)
Design & Maintainability
(level 1 and 2 only)

Class Design

  • A class or interface should have a single purpose (AV1000)
  • An interface should be small and focused (AV1003)
  • Use an interface to decouple classes from each other (AV1005)
  • Don’t suppress compiler warnings using the new keyword (AV1010)
  • It should be possible to treat a derived object as if it were a base class object (AV1011)
  • Don’t refer to derived classes from the base class (AV1013)
  • Avoid exposing the other objects an object depends on (AV1014)
  • Avoid bidirectional dependencies (AV1020)
  • Classes should have state and behavior (AV1025)
  • Classes should protect the consistency of their internal state (AV1026)

Member Design

  • Allow properties to be set in any order (AV1100)
  • Don’t use mutually exclusive properties (AV1110)
  • A property, method or local function should do only one thing (AV1115)
  • Don’t expose stateful objects through static members (AV1125)
  • Return an IEnumerable<T> or ICollection<T> instead of a concrete collection class (AV1130)
  • Properties, arguments and return values representing strings, collections or tasks should never be null (AV1135)
  • Define parameters as specific as possible (AV1137)
**Miscellaneous Design** * Throw exceptions rather than returning some kind of status value (AV1200) * Provide a rich and meaningful exception message text (AV1202) * Don't swallow errors by catching generic exceptions (AV1210) * Properly handle exceptions in asynchronous code (AV1215) * Always check an event handler delegate for `null` (AV1220) * Use a protected virtual method to raise each event (AV1225) * Don't pass `null` as the `sender` argument when raising an event (AV1235) * Use generic constraints if applicable (AV1240) * Evaluate the result of a LINQ expression before returning it (AV1250) * Do not use `this` and `base` prefixes unless it is required (AV1251)
**Maintainability** * Methods should not exceed 7 statements (AV1500) * Make all members `private` and types `internal sealed` by default (AV1501) * Avoid conditions with double negatives (AV1502) * Don't use "magic" numbers (AV1515) * Only use `var` when the type is very obvious (AV1520) * Declare and initialize variables as late as possible (AV1521) * Assign each variable in a separate statement (AV1522) * Favor object and collection initializers over separate statements (AV1523) * Don't make explicit comparisons to `true` or `false` (AV1525) * Don't change a loop variable inside a `for` loop (AV1530) * Avoid nested loops (AV1532)
* Always add a block after the keywords `if`, `else`, `do`, `while`, `for`, `foreach` and `case` (AV1535) * Always add a `default` block after the last `case` in a `switch` statement (AV1536) * Finish every `if`-`else`-`if` statement with an `else` clause (AV1537) * Be reluctant with multiple `return` statements (AV1540) * Don't use an `if`-`else` construct instead of a simple (conditional) assignment (AV1545) * Encapsulate complex expressions in a property, method or local function (AV1547) * Call the more overloaded method from other overloads (AV1551) * Only use optional parameters to replace overloads (AV1553) * Do not use optional parameters in interface methods or their concrete implementations (AV1554) * Avoid using named arguments (AV1555) * Don't declare signatures with more than 3 parameters (AV1561) * Don't use `ref` or `out` parameters (AV1562) * Avoid signatures that take a `bool` flag (AV1564) * Prefer `is` patterns over `as` operations (AV1570) * Don't comment out code (AV1575) * Write code that is easy to debug (AV1580)
**Framework Guidelines** * Use C# type aliases instead of the types from the `System` namespace (AV2201) * Prefer language syntax over explicit calls to underlying implementations (AV2202) * Build with the highest warning level (AV2210) * Use lambda expressions instead of anonymous methods (AV2221) * Only use the `dynamic` keyword when talking to a dynamic object (AV2230) * Favor `async`/`await` over `Task` continuations (AV2235)


Coding Guidelines for C# v10 Cheat Sheet

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Naming & Layout
(level 1 and 2 only)


  • Use US English (AV1701)
  • Don’t prefix fields (AV1705)
  • Don’t use abbreviations (AV1706)
  • Name members, parameters and variables according to their meaning and not their type (AV1707)
  • Name types using nouns, noun phrases or adjective phrases (AV1708)
  • Name generic type parameters with descriptive names (AV1709)
  • Don’t repeat the name of a class or enumeration in its members (AV1710)
  • Avoid short names or names that can be mistaken for other names (AV1712)
  • Properly name properties (AV1715)
  • Name methods and local functions using verbs or verb-object pairs (AV1720)
  • Use a verb or verb phrase to name an event (AV1735)
  • Postfix asynchronous methods with Async or TaskAsync (AV1755)
* Use an underscore for irrelevant parameters (AV1739) **Documentation** * Write comments and documentation in US English (AV2301) * Document all `public`, `protected` and `internal` types and members (AV2305) * Write XML documentation with other developers in mind (AV2306) * Avoid inline comments (AV2310) * Only write comments to explain complex algorithms or decisions (AV2316)
**Layout** * Maximum line length is 130 characters * Indent 4 spaces, don't use tabs * Keep one space between keywords like `if` and the expression, but don't add spaces after `(` and before `)` * Add a space around operators, like `+`, `-`, `==`, etc. * Always add curly braces after the keywords `if`, `else`, `do`, `while`, `for`, `foreach` and `case` (AV1535) * Always put opening and closing curly braces on a new line * Don't indent object/collection initializers and initialize each property on a new line * Don't indent lambda statement blocks * Keep expression-bodied-members on one line; break long lines after the arrow sign * Put the entire LINQ statement on one line, or start each keyword at the same indentation * Remove redundant parentheses in expressions if they do not clarify precedence; add parentheses in expressions to avoid non-obvious precedence
* Do not use `#region` (AV2407) * Use expression-bodied members appropriately (AV2410)