---
title: "CustomFormatReader..::.OnOpen Method "
canonical: https://www.graphicsmill.com/docs/gm5/M_Aurigma_GraphicsMill_Codecs_CustomFormatReader_OnOpen.htm
product: "Graphics Mill 5.5 for .NET"
---

This documentation is for the old version. [Go to the latest Graphics Mill docs](https://www.graphicsmill.com/docs/gm/)

# CustomFormatReader.OnOpen Method 
 
Called when the reader is opened.
 
**Namespace:** [Aurigma.GraphicsMill.Codecs](https://www.graphicsmill.com/docs/gm5/N_Aurigma_GraphicsMill_Codecs.htm.md)
 **Assembly:** Aurigma.GraphicsMill (in Aurigma.GraphicsMill.dll)
 
## Syntax
  
```
Protected Friend Overrides Sub OnOpen
```
 
```csharp
protected internal override void OnOpen()
```
 
## Remarks
  
Do not implement this method. Implement the [OpenReader(String)](https://www.graphicsmill.com/docs/gm5/M_Aurigma_GraphicsMill_Codecs_CustomFormatReader_OpenReader_1_bb3a7a4f.htm.md) instead.
   
## See Also

### Reference

- [CustomFormatReader Class](https://www.graphicsmill.com/docs/gm5/T_Aurigma_GraphicsMill_Codecs_CustomFormatReader.htm.md)
- [Aurigma.GraphicsMill.Codecs Namespace](https://www.graphicsmill.com/docs/gm5/N_Aurigma_GraphicsMill_Codecs.htm.md)
- [FormatReader.Open(String)](https://www.graphicsmill.com/docs/gm5/M_Aurigma_GraphicsMill_Codecs_FormatReader_Open_1_bb3a7a4f.htm.md)