> ## 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.

# AL0104 - Prefer 'await using' for IAsyncDisposable

> 'using' calls sync Dispose() instead of DisposeAsync()

Source: [Al0104PreferAwaitUsingAnalyzer.cs](https://github.com/ANcpLua/ANcpLua.Analyzers/blob/main/src/ANcpLua.Analyzers/Analyzers/Al0104PreferAwaitUsingAnalyzer.cs)

## Description

When a type implements `IAsyncDisposable`, using `using` instead of `await using` calls the synchronous `Dispose()` method, potentially blocking or skipping async cleanup.

## Bad Code

```csharp theme={null}
async Task Process()
{
    using var conn = new SqlConnection(connString);
    await conn.OpenAsync();
}
```

## Good Code

```csharp theme={null}
async Task Process()
{
    await using var conn = new SqlConnection(connString);
    await conn.OpenAsync();
}
```

## Properties

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

## Configuration

```editorconfig theme={null}
dotnet_diagnostic.AL0104.severity = warning
```