You have declared a function outside of a class. You cannot do that in C# - all code must be within a class.
You have also forgotten to provide a method body.
namespace TextEditor.Pages
{
public static class RichEditExtensions
{
public static RichEditBuilder RichEdit(
this BuilderFactory factory,
string name)
{
throw new NotImplementedException();
}
}
}
But this raises the question of why you are trying to implement a method which the DevExpress framework already provides for you?
BuilderFactoryRichEditExtensions.RichEdit(BuilderFactory, String) Method | ASP.NET Core Controls | DevExpress Documentation[
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