Line Number Provider

A line number provider allows the line numbers displayed in a line number margin to be customized. While any string value can be displayed for each view line, one-based integers are most commonly used.

Basic Concepts

Line number providers are classes implementing ITextViewLineNumberProvider that can return the display text for each view line that should appear in the line number margin. The GetLineNumberText method is called for each view line and a string is returned containing the line number display text. This typically is a one-based integer number converted to a string.

The language service also defines a GetLargestLineNumberText that returns the known longest line number text, used for measuring purposes.

The DefaultTextViewLineNumberProvider class implements the ITextViewLineNumberProvider interface and provides a default implementation for one-based integer line numbers. It has several virtual methods that can be overridden to customize results. An instance of DefaultTextViewLineNumberProvider is used if no custom line number provider language service is set.

Setting the Line Number Origin

The IEditorDocument.LineNumberOrigin property is the origin line number to use as the base for the first view line. It defaults to 1 but can be set to any other number as needed. The DefaultTextViewLineNumberProvider implementation uses this origin value for the first view line.

For instance, if the first view line in a document is meant to represent the 400th line in some code snippet, set the origin to 400.

Registering with a Language

Any object that implements ITextViewLineNumberProvider can be associated with a syntax language by registering it as an ITextViewLineNumberProvider service on the language.

This code creates a DefaultTextViewLineNumberProvider object and registers it with the syntax language that is already declared in the language variable:

DefaultTextViewLineNumberProvider lineNumberProvider = new DefaultTextViewLineNumberProvider();
language.RegisterTextViewLineNumberProvider(lineNumberProvider);