# IsKnownExtension(string)

> Checks if files with the given extension are known to PBXProject.

## Definition

* **Type:** Method
* **Namespace:** [UnityEditor.iOS.Xcode](/engine/6000.5/script-reference/unityeditor/ios/xcode.md)
* **Assembly:** UnityEditor.iOS.Extensions.Xcode

```csharp
public static bool IsKnownExtension(string ext)
```

### Parameters

**** (\[string]\(https\://learn.microsoft.com/dotnet/api/system.string)): The file extension. The leading `.` is not necessary but is accepted.

### Returns

| Type                                                          | Description                             |
| ------------------------------------------------------------- | --------------------------------------- |
| [bool](https://learn.microsoft.com/dotnet/api/system.boolean) | Returns true of the extension is known. |

### Examples

```csharp
using UnityEngine;
using UnityEditor;
using UnityEditor.Callbacks;
using UnityEditor.iOS.Xcode;

public class Sample_IsKnownExtension  
{
    [PostProcessBuild]
    public static void OnPostprocessBuild(BuildTarget buildTarget, string pathToBuiltProject)
    {
        // Specify file extension you want to check
        string extension = "txt";

        // Check if the file extension is known to PBXProject
        bool isKnown = PBXProject.IsKnownExtension(extension);
        Debug.Log("Extension " + extension + " " + (isKnown ? "is" : "is not") + " known to PBXProject");
    }
}
```