Pros and cons of having static repositories in ASP.NET MVC application

What are the pros and cons of using static repositories in an ASP.NET MVC application?

Wouldn't it be bette开发者_开发技巧r to have all the methods available all the time -> means that the class get's instantiated only once instead of having multiple controllers referencing to the same repository class and its methods?

Or do I get something wrong here?

All help is more than appreciated!

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Pros:

• Repository is accessible everywhere

Cons:

• Repositories don't implement a contract which leads to a strong coupling between consumers of the repository and the implementation
• Impossible to unit test
• Might run into threading issues

Remark: Instantiating the repository on every request shouldn't be regarded as a performance issue.