Applying for a job without prior experience in related field?

I've been working with my current company for the past 3 years doing mainly web-based applications using php and mysql. Now, after 3 years I think that I'm done with php and mysql and wanted to try something new instead. .NET programming to be specific. The problem is that I had never ever develop anything with .NET before. Suffice to say I had zero experience with .NET programming. Now, there is one particular job vacancy that I'm interested with. Well, like most other job requirement, the job requires at least 3 years of working experience in the related field along with other knowledge about all kinds of Microsoft technologies related to .NET which I do not have and do not know. To be honest, the only reason why I'm interested in applying for this job is because I wanted to try .NET programming. As a programmer I always believe that I have to have basic knowledge of different kind of programming language. I am sure that I can learn .NET programming if given the time and chance. As a matter of fact I self taught myself php and mysql by reading books, online articles, tutorials and etc. The problem now is how can I convince them that I am actually the right person for the job even without any prior experience with .NET. What is the best way to convince and tell them. I can't just say that I wanted to try something new now can I?