Hello Marco,

The LineNumberMargin that displays a number for each line of the current document is in the Margins collection of RadSyntaxEditor. You can remove it as shown below:

this.radSyntaxEditor1.SyntaxEditorElement.Margins.ScrollableLeft.RemoveAt(0);

However, exposing a public API that sets the LineNumberMargin to be visible or not sounds like a reasonable request. This is why I have logged it in our feedback portal by making this thread public. You can track its progress, subscribe for status changes and add your comments on the following link - feedback item.

I have also updated your Telerik Points.

I hope this helps. Should you have any other questions, I will be glad to help.

Regards,
Nadya
Progress Telerik