csharp-coding-standards

Name: csharp-coding-standards
Author: Aaronontheweb

1.1kstars98forks

How to install csharp-coding-standards?

aaronontheweb/dotnet-skills/csharp-coding-standards

$npx -y skills add Aaronontheweb/dotnet-skills --skill csharp-coding-standards

Installs into the current project.

Summary

Write modern, high-performance C# code using records, pattern matching, value objects, async/await, Span<T>/Memory<T>, and best-practice API design patterns. Emphasizes functional-style programming with C# 12+ features.

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SKILL.md

1	# Modern C# Coding Standards
2
3	## When to Use This Skill
4
5	Use this skill when:
6	- Writing new C# code or refactoring existing code
7	- Designing public APIs for libraries or services
8	- Optimizing performance-critical code paths
9	- Implementing domain models with strong typing
10	- Building async/await-heavy applications
11	- Working with binary data, buffers, or high-throughput scenarios
12
13	## Reference Files
14
15	- [value-objects-and-patterns.md](value-objects-and-patterns.md): Full value object examples and pattern matching code
16	- [performance-and-api-design.md](performance-and-api-design.md): Span<T>/Memory<T> examples and API design principles
17	- [composition-and-error-handling.md](composition-and-error-handling.md): Composition over inheritance, Result type, testing patterns
18	- [anti-patterns-and-reflection.md](anti-patterns-and-reflection.md): Reflection avoidance and common anti-patterns
19
20	## Core Principles
21
22	1. Immutability by Default - Use `record` types and `init`-only properties
23	2. Type Safety - Leverage nullable reference types and value objects
24	3. Modern Pattern Matching - Use `switch` expressions and patterns extensively
25	4. Async Everywhere - Prefer async APIs with proper cancellation support
26	5. Zero-Allocation Patterns - Use `Span<T>` and `Memory<T>` for performance-critical code
27	6. API Design - Accept abstractions, return appropriately specific types
28	7. Composition Over Inheritance - Avoid abstract base classes, prefer composition
29	8. Value Objects as Structs - Use `readonly record struct` for value objects
30
31	---
32
33	## Language Patterns
34
35	### Records for Immutable Data (C# 9+)
36
37	Use `record` types for DTOs, messages, events, and domain entities.
38
39	```csharp
40	// Simple immutable DTO
41	public record CustomerDto(string Id, string Name, string Email);
42
43	// Record with validation in constructor
44	public record EmailAddress
45	{
46	public string Value { get; init; }
47
48	public EmailAddress(string value)
49	{
50	if (string.IsNullOrWhiteSpace(value) \|\| !value.Contains('@'))
51	throw new ArgumentException("Invalid email address", nameof(value));
52
53	Value = value;
54	}
55	}
56
57	// Records with collections - use IReadOnlyList
58	public record ShoppingCart(
59	string CartId,
60	string CustomerId,
61	IReadOnlyList<CartItem> Items
62	)
63	{
64	public decimal Total => Items.Sum(item => item.Price * item.Quantity);
65	}
66	```
67
68	When to use `record class` vs `record struct`:
69	- `record class` (default): Reference types, use for entities, aggregates, DTOs with multiple properties
70	- `record struct`: Value types, use for value objects (see next section)
71
72	### Value Objects as readonly record struct
73
74	Value objects should always be `readonly record struct` for performance and value semantics. Use explicit conversions, never implicit operators.
75
76	```csharp
77	public readonly record struct OrderId(string Value)
78	{
79	public OrderId(string value) : this(
80	!string.IsNullOrWhiteSpace(value)
81	? value
82	: throw new ArgumentException("OrderId cannot be empty", nameof(value)))
83	{ }
84	public override string ToString() => Value;
85	}
86
87	public readonly record struct Money(decimal Amount, string Currency);
88	public readonly record struct CustomerId(Guid Value)
89	{
90	public static CustomerId New() => new(Guid.NewGuid());
91	}
92	```
93
94	See [value-objects-and-patterns.md](value-objects-and-patterns.md) for complete examples including multi-value objects, factory patterns, and the no-implicit-conversion rule.
95
96	### Pattern Matching (C# 8-12)
97
98	Use switch expressions, property patterns, relational patterns, and list patterns for cleaner code.
99
100	```csharp
101	public decimal CalculateDiscount(Order order) => order switch
102	{
103	{ Total: > 1000m } => order.Total * 0.15m,
104	{ Total: > 500m } => order.Total * 0.10m,
105	{ Total: > 100m } => order.Total * 0.05m,
106	_ => 0m
107	};
108	```
109
110	See [value-objects-and-patterns.md](value-objects-and-patterns.md) for full pattern matching examples.
111
112	---
113
114	### Nullable Reference Types (C# 8+)
115
116	Enable nullable reference types in your project and handle nulls explicitly.
117
118	```csharp
119	// In .csproj
120	<PropertyGroup>
121	<Nullable>enable</Nullable>
122	</PropertyGroup>
123
124	// Explicit nullability
125	public string? FindUserName(string userId)
126	{
127	var user = _repository.Find(userId);
128	return user?.Name;
129	}
130
131	// Pattern matching with null checks
132	public decimal GetDiscount(Customer? customer) => customer switch
133	{
134	null => 0m,
135	{ IsVip: true } => 0.20m,
136	{ OrderCount: > 10 } => 0.10m,
137	_ => 0.05m
138	};
139
140	// Guard clauses with ArgumentNullException.ThrowIfNull (C# 11+)
141	public void ProcessOrder(Order? order)
142	{
143	ArgumentNullException.ThrowIfNull(order);
144	// order is now non-nullable in this scope
145	Con

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Type

csharp-coding-standards

1.1kstars98forks

View on GitHub

How to install csharp-coding-standards?

aaronontheweb/dotnet-skills/csharp-coding-standards

$npx -y skills add Aaronontheweb/dotnet-skills --skill csharp-coding-standards

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Modern C# Coding Standards
2
3	## When to Use This Skill
4
5	Use this skill when:
6	- Writing new C# code or refactoring existing code
7	- Designing public APIs for libraries or services
8	- Optimizing performance-critical code paths
9	- Implementing domain models with strong typing
10	- Building async/await-heavy applications
11	- Working with binary data, buffers, or high-throughput scenarios
12
13	## Reference Files
14
15	- [value-objects-and-patterns.md](value-objects-and-patterns.md): Full value object examples and pattern matching code
16	- [performance-and-api-design.md](performance-and-api-design.md): Span<T>/Memory<T> examples and API design principles
17	- [composition-and-error-handling.md](composition-and-error-handling.md): Composition over inheritance, Result type, testing patterns
18	- [anti-patterns-and-reflection.md](anti-patterns-and-reflection.md): Reflection avoidance and common anti-patterns
19
20	## Core Principles
21
22	1. Immutability by Default - Use `record` types and `init`-only properties
23	2. Type Safety - Leverage nullable reference types and value objects
24	3. Modern Pattern Matching - Use `switch` expressions and patterns extensively
25	4. Async Everywhere - Prefer async APIs with proper cancellation support
26	5. Zero-Allocation Patterns - Use `Span<T>` and `Memory<T>` for performance-critical code
27	6. API Design - Accept abstractions, return appropriately specific types
28	7. Composition Over Inheritance - Avoid abstract base classes, prefer composition
29	8. Value Objects as Structs - Use `readonly record struct` for value objects
30
31	---
32
33	## Language Patterns
34
35	### Records for Immutable Data (C# 9+)
36
37	Use `record` types for DTOs, messages, events, and domain entities.
38
39	```csharp
40	// Simple immutable DTO
41	public record CustomerDto(string Id, string Name, string Email);
42
43	// Record with validation in constructor
44	public record EmailAddress
45	{
46	public string Value { get; init; }
47
48	public EmailAddress(string value)
49	{
50	if (string.IsNullOrWhiteSpace(value) \|\| !value.Contains('@'))
51	throw new ArgumentException("Invalid email address", nameof(value));
52
53	Value = value;
54	}
55	}
56
57	// Records with collections - use IReadOnlyList
58	public record ShoppingCart(
59	string CartId,
60	string CustomerId,
61	IReadOnlyList<CartItem> Items
62	)
63	{
64	public decimal Total => Items.Sum(item => item.Price * item.Quantity);
65	}
66	```
67
68	When to use `record class` vs `record struct`:
69	- `record class` (default): Reference types, use for entities, aggregates, DTOs with multiple properties
70	- `record struct`: Value types, use for value objects (see next section)
71
72	### Value Objects as readonly record struct
73
74	Value objects should always be `readonly record struct` for performance and value semantics. Use explicit conversions, never implicit operators.
75
76	```csharp
77	public readonly record struct OrderId(string Value)
78	{
79	public OrderId(string value) : this(
80	!string.IsNullOrWhiteSpace(value)
81	? value
82	: throw new ArgumentException("OrderId cannot be empty", nameof(value)))
83	{ }
84	public override string ToString() => Value;
85	}
86
87	public readonly record struct Money(decimal Amount, string Currency);
88	public readonly record struct CustomerId(Guid Value)
89	{
90	public static CustomerId New() => new(Guid.NewGuid());
91	}
92	```
93
94	See [value-objects-and-patterns.md](value-objects-and-patterns.md) for complete examples including multi-value objects, factory patterns, and the no-implicit-conversion rule.
95
96	### Pattern Matching (C# 8-12)
97
98	Use switch expressions, property patterns, relational patterns, and list patterns for cleaner code.
99
100	```csharp
101	public decimal CalculateDiscount(Order order) => order switch
102	{
103	{ Total: > 1000m } => order.Total * 0.15m,
104	{ Total: > 500m } => order.Total * 0.10m,
105	{ Total: > 100m } => order.Total * 0.05m,
106	_ => 0m
107	};
108	```
109
110	See [value-objects-and-patterns.md](value-objects-and-patterns.md) for full pattern matching examples.
111
112	---
113
114	### Nullable Reference Types (C# 8+)
115
116	Enable nullable reference types in your project and handle nulls explicitly.
117
118	```csharp
119	// In .csproj
120	<PropertyGroup>
121	<Nullable>enable</Nullable>
122	</PropertyGroup>
123
124	// Explicit nullability
125	public string? FindUserName(string userId)
126	{
127	var user = _repository.Find(userId);
128	return user?.Name;
129	}
130
131	// Pattern matching with null checks
132	public decimal GetDiscount(Customer? customer) => customer switch
133	{
134	null => 0m,
135	{ IsVip: true } => 0.20m,
136	{ OrderCount: > 10 } => 0.10m,
137	_ => 0.05m
138	};
139
140	// Guard clauses with ArgumentNullException.ThrowIfNull (C# 11+)
141	public void ProcessOrder(Order? order)
142	{
143	ArgumentNullException.ThrowIfNull(order);
144	// order is now non-nullable in this scope
145	Con

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Type