A Delaware-based company is claiming that Microsoft's widely used .Net software development framework infringes on a patent it holds.

In court papers filed last week in U.S. District Court for Eastern Texas, Vertical Computer Systems charges that the .Net framework violates U.S. Patent 6,826,744, which describes a "system and method for generating Web sites in an arbitrary object framework."

Vertical Computer Systems was awarded the patent in November, 2004.

The company says that in February it informed Microsoft in writing that it believes .Net violates its patent. "Since that time, Microsoft has been willfully infringing" the patent, the lawsuit charges.

Vertical Computer Systems says the patent protects its SiteFlash product. The XML-based technology "enables the user to build and efficiently operate Web sites with the unique ability to separate form, function, and content," according to the company's Web site.

Vertical Computer Systems is seeking unspecified damages. Microsoft has yet to file a formal response in the case.