> ## Documentation Index
> Fetch the complete documentation index at: https://ancplua.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# AL0039 - Use StringComparison extensions

> Replace string methods with StringComparison parameter using named extensions

Source: [AL0039UseStringComparisonExtensionsAnalyzer.cs](https://github.com/ANcpLua/ANcpLua.Analyzers/blob/main/src/ANcpLua.Analyzers/Analyzers/AL0039UseStringComparisonExtensionsAnalyzer.cs)

## Description

String methods with `StringComparison` enum parameters are less readable. ANcpLua.Roslyn.Utilities provides named extension methods for clearer intent.

## Bad Code

```csharp theme={null}
// Verbose StringComparison parameters
if (value.Equals("Warning", StringComparison.OrdinalIgnoreCase)) { }
if (path.StartsWith("/api/", StringComparison.Ordinal)) { }
if (text.Contains("error", StringComparison.OrdinalIgnoreCase)) { }
```

## Good Code

```csharp theme={null}
using ANcpLua.Roslyn.Utilities;

// Clear intent with named extensions
if (value.EqualsIgnoreCase("Warning")) { }
if (path.StartsWithOrdinal("/api/")) { }
if (text.ContainsIgnoreCase("error")) { }
```

## Properties

* **Category**: Usage
* **Severity**: Warning
* **Enabled by default**: True
* **Code fix available**: True

## Configuration

```editorconfig theme={null}
dotnet_diagnostic.AL0039.severity = warning
```

## Available Extensions

| Method     | Ordinal               | IgnoreCase               |
| ---------- | --------------------- | ------------------------ |
| Equals     | `EqualsOrdinal()`     | `EqualsIgnoreCase()`     |
| StartsWith | `StartsWithOrdinal()` | `StartsWithIgnoreCase()` |
| EndsWith   | `EndsWithOrdinal()`   | `EndsWithIgnoreCase()`   |
| Contains   | `ContainsOrdinal()`   | `ContainsIgnoreCase()`   |
| IndexOf    | `IndexOfOrdinal()`    | `IndexOfIgnoreCase()`    |

## Limitations

* **`LastIndexOf`** is not flagged - no extension method exists
* **`IndexOf` with startIndex** is not flagged - extensions only support simple `(value, StringComparison)` signatures