> For the complete documentation index, see [llms.txt](https://docs.yarnspinner.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.yarnspinner.dev/3.1/api/csharp/yarn.compiler/yarn.compiler.declarationbuilder/yarn.compiler.declarationbuilder.withsourcefilename.md).

# WithSourceFileName(string)

Method in [DeclarationBuilder](/3.1/api/csharp/yarn.compiler/yarn.compiler.declarationbuilder.md)

## Summary

Sets the [SourceFileName](/3.1/api/csharp/yarn.compiler/yarn.compiler.declaration/yarn.compiler.declaration.sourcefilename.md) of the [Declaration](/3.1/api/csharp/yarn.compiler/yarn.compiler.declarationbuilder/yarn.compiler.declarationbuilder.declaration.md) .

```csharp
public DeclarationBuilder WithSourceFileName(string sourceFileName)
```

## Parameters

| Name                    | Description                                       |
| ----------------------- | ------------------------------------------------- |
| `string` sourceFileName | The source file name to apply to the Declaration. |

## Returns

The [DeclarationBuilder](/3.1/api/csharp/yarn.compiler/yarn.compiler.declarationbuilder.md) instance that received this method call.