dotnet-quality

What this skill does

# .NET Quality - Quick Reference

## When NOT to Use This Skill
- **SonarQube setup** - Use `sonarqube` skill
- **Security scanning** - Use `dotnet-security` skill
- **Testing** - Use .NET test skills

> **Deep Knowledge**: Use `mcp__documentation__fetch_docs` with technology: `dotnet` for comprehensive documentation.

## Tool Overview

| Tool | Focus | Installation |
|------|-------|--------------|
| **dotnet format** | Formatting + analyzers | Built-in |
| **Roslyn Analyzers** | Code analysis | NuGet |
| **StyleCop.Analyzers** | Style rules | NuGet |
| **Roslynator** | Refactoring | NuGet |
| **SonarAnalyzer.CSharp** | SonarQube rules | NuGet |

## Roslyn Analyzers Setup

### Install Analyzers

```xml
<!-- Directory.Build.props (solution-wide) -->
<Project>
  <PropertyGroup>
    <AnalysisLevel>latest-all</AnalysisLevel>
    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="8.0.0">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
    </PackageReference>
    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Roslynator.Analyzers" Version="4.10.0">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
    </PackageReference>
  </ItemGroup>
</Project>
```

### .editorconfig

```ini
# .editorconfig
root = true

[*]
indent_style = space
indent_size = 4
end_of_line = lf
charset = utf-8
trim_trailing_whitespace = true
insert_final_newline = true

[*.cs]
# Organize usings
dotnet_sort_system_directives_first = true
dotnet_separate_import_directive_groups = false

# this. qualification
dotnet_style_qualification_for_field = false:warning
dotnet_style_qualification_for_property = false:warning
dotnet_style_qualification_for_method = false:warning
dotnet_style_qualification_for_event = false:warning

# Language keywords vs BCL types
dotnet_style_predefined_type_for_locals_parameters_members = true:warning
dotnet_style_predefined_type_for_member_access = true:warning

# var preferences
csharp_style_var_for_built_in_types = true:suggestion
csharp_style_var_when_type_is_apparent = true:suggestion
csharp_style_var_elsewhere = true:suggestion

# Expression-bodied members
csharp_style_expression_bodied_methods = when_on_single_line:suggestion
csharp_style_expression_bodied_constructors = false:suggestion
csharp_style_expression_bodied_properties = true:suggestion
csharp_style_expression_bodied_accessors = true:suggestion
csharp_style_expression_bodied_lambdas = true:suggestion

# Pattern matching
csharp_style_pattern_matching_over_is_with_cast_check = true:warning
csharp_style_pattern_matching_over_as_with_null_check = true:warning

# Null checking
csharp_style_throw_expression = true:suggestion
csharp_style_conditional_delegate_call = true:warning
dotnet_style_coalesce_expression = true:warning
dotnet_style_null_propagation = true:warning

# Code style
csharp_prefer_braces = true:warning
csharp_prefer_simple_using_statement = true:suggestion
csharp_style_prefer_switch_expression = true:suggestion

# Naming conventions
dotnet_naming_rule.interface_should_be_begins_with_i.severity = warning
dotnet_naming_rule.interface_should_be_begins_with_i.symbols = interface
dotnet_naming_rule.interface_should_be_begins_with_i.style = begins_with_i

dotnet_naming_symbols.interface.applicable_kinds = interface
dotnet_naming_symbols.interface.applicable_accessibilities = public, internal, private, protected
dotnet_naming_style.begins_with_i.required_prefix = I
dotnet_naming_style.begins_with_i.capitalization = pascal_case

dotnet_naming_rule.private_field_should_be_camel_case_with_underscore.severity = warning
dotnet_naming_rule.private_field_should_be_camel_case_with_underscore.symbols = private_field
dotnet_naming_rule.private_field_should_be_camel_case_with_underscore.style = camel_case_underscore

dotnet_naming_symbols.private_field.applicable_kinds = field
dotnet_naming_symbols.private_field.applicable_accessibilities = private
dotnet_naming_style.camel_case_underscore.required_prefix = _
dotnet_naming_style.camel_case_underscore.capitalization = camel_case

# Analyzer severity
dotnet_diagnostic.CA1062.severity = warning  # Validate arguments
dotnet_diagnostic.CA1307.severity = warning  # Specify StringComparison
dotnet_diagnostic.CA1310.severity = warning  # Specify StringComparison for correctness
dotnet_diagnostic.CA2007.severity = none     # ConfigureAwait (not needed in ASP.NET Core)
dotnet_diagnostic.IDE0058.severity = none    # Expression value never used

# StyleCop
dotnet_diagnostic.SA1101.severity = none     # Prefix local calls with this
dotnet_diagnostic.SA1309.severity = none     # Field names must not begin with underscore
dotnet_diagnostic.SA1600.severity = none     # Elements should be documented
dotnet_diagnostic.SA1633.severity = none     # File should have header
```

## dotnet format

### Commands

```bash
# Check formatting
dotnet format --verify-no-changes

# Fix formatting
dotnet format

# Specific project
dotnet format ./src/MyProject

# Analyzers only
dotnet format analyzers

# Style only
dotnet format style

# Whitespace only
dotnet format whitespace

# With severity
dotnet format --severity warn
```

## Common Analyzer Warnings

### CA1062 - Validate Arguments

```csharp
// BAD - No null check
public void Process(string input)
{
    Console.WriteLine(input.Length);  // CA1062
}

// GOOD - Null check
public void Process(string input)
{
    ArgumentNullException.ThrowIfNull(input);
    Console.WriteLine(input.Length);
}

// GOOD - Nullable reference type
public void Process(string? input)
{
    if (input is null) return;
    Console.WriteLine(input.Length);
}
```

### CA1307/CA1310 - StringComparison

```csharp
// BAD - Culture-dependent
if (name.Equals("admin"))  // CA1307

// GOOD - Explicit comparison
if (name.Equals("admin", StringComparison.OrdinalIgnoreCase))

// GOOD - For user-facing
if (name.Equals(otherName, StringComparison.CurrentCultureIgnoreCase))
```

### CA2000 - Dispose Objects

```csharp
// BAD - Not disposed
public void Process()
{
    var stream = new FileStream("file.txt", FileMode.Open);  // CA2000
    // forgot to dispose
}

// GOOD - Using statement
public void Process()
{
    using var stream = new FileStream("file.txt", FileMode.Open);
    // automatically disposed
}
```

### IDE0090 - Use Target-typed new

```csharp
// Before
List<string> items = new List<string>();

// After
List<string> items = new();

// Or with var
var items = new List<string>();
```

## Common Code Smells & Fixes

### 1. God Class

```csharp
// BAD - Does too much
public class OrderProcessor
{
    public void CreateOrder() { ... }
    public void SendEmail() { ... }
    public void GeneratePdf() { ... }
    public void CalculateTax() { ... }
}

// GOOD - Single responsibility
public class OrderService
{
    private readonly IEmailService _emailService;
    private readonly IPdfGenerator _pdfGenerator;
    private readonly ITaxCalculator _taxCalculator;

    public OrderService(
        IEmailService emailService,
        IPdfGenerator pdfGenerator,
        ITaxCalculator taxCalculator)
    {
        _emailService = emailService;
        _pdfGenerator = pdfGenerator;
        _taxCalculator = taxCalculator;
    }

    public async Task<Order> CreateOrderAsync(OrderRequest request)
    {
        var order = BuildOrder(request);
        order.Tax = _taxCalculator.Calculate(order);
        return order;
    }
}
```

### 2. Async/Await Pitfalls

```csharp
// BAD - Blocking async
public void Process()
{
    var result = GetDataAsync().Result;  /