> ## 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.

# AL0040 - Use attribute extensions

> Replace direct AttributeData access with GetConstructorArgument/GetNamedArgument extensions

Source: [AL0040UseAttributeExtensionsAnalyzer.cs](https://github.com/ANcpLua/ANcpLua.Analyzers/blob/main/src/ANcpLua.Analyzers/Analyzers/AL0040UseAttributeExtensionsAnalyzer.cs)

## Description

Direct access to `AttributeData.ConstructorArguments[i].Value` is verbose and error-prone. ANcpLua.Roslyn.Utilities provides typed extraction extensions.

## Bad Code

```csharp theme={null}
using Microsoft.CodeAnalysis;

// Verbose attribute argument access
var typeArg = (ITypeSymbol?)attr.ConstructorArguments[0].Value;
var name = attr.NamedArguments.FirstOrDefault(x => x.Key == "Name").Value.Value as string;
```

## Good Code

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

// Type-safe extraction
var typeArg = attr.GetConstructorArgument<ITypeSymbol>(0);
var name = attr.GetNamedArgument<string>("Name");
```

## Properties

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

## Configuration

```editorconfig theme={null}
dotnet_diagnostic.AL0040.severity = warning
```

## Notes

* `GetConstructorArgument<T>(index)` - type-safe positional argument extraction
* `GetNamedArgument<T>(name)` - type-safe named argument extraction
* Handles null and type conversion gracefully
* Common pattern in Roslyn analyzer development