> ## 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.

# AL0034 - Use WhereNotNull()

> Replace Where(x => x != null) with WhereNotNull() extension

Source: [AL0034UseWhereNotNullAnalyzer.cs](https://github.com/ANcpLua/ANcpLua.Analyzers/blob/main/src/ANcpLua.Analyzers/Analyzers/AL0034UseWhereNotNullAnalyzer.cs)

## Description

Filtering null values with `Where(x => x != null)` is a common pattern that can be simplified using the `WhereNotNull()` extension.

## Bad Code

```csharp theme={null}
// Verbose null filtering
var nonNull = items.Where(x => x != null);
var filtered = symbols.Where(s => s is not null);
```

## Good Code

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

// Clean extension
var nonNull = items.WhereNotNull();
var filtered = symbols.WhereNotNull();
```

## Properties

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

## Configuration

```editorconfig theme={null}
dotnet_diagnostic.AL0034.severity = suggestion
```

## Notes

* Also changes the return type from `IEnumerable<T?>` to `IEnumerable<T>`
* Eliminates nullable warnings in subsequent code
* Clearer intent than explicit null check