Visual Studio: Turn on line numbering

Many development tools—e.g. FxCop—refer to source code line numbers. Visual Studio .NET always shows the current line number, but finding a particular line called out by a tool is simpler if source code line numbering is enabled.
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Change Visual Studio Options

The grid layout settings are found on the Visual Studio 2005 Options dialog box. To access the Options dialog box, select the Tools / Options… menus. It is the same in the Visual Studio Express Editions.
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Check Line numbers

* Expand the Text Editor item in the left panel of the Options dialog box.

* Select the C# item.

* Enable source code line numbering by checking the Line numbers checkbox in the Display section of the right panel. Click the OK button and voilá—line numbers!