Code Contract understanding of error

Question

I am just getting started with Code Contracts, and need a little help in correcting an error:

Given this code:

class MyClass
{
    private bool _isUsed = false;

    public void SomeMethod()
    {
        Contract.Requires(!_isUsed);
    }
}

I get the following error:

error CC1038: Member 'MyClass._isUsed' has less visibility than the enclosing method 'MyClass.SomeMethod'

which seems to makes alot of the standard checks unavailable. What am I missing in this example?

Answer 1

You have a public method SomeMethod. However, you're requiring that a private member variable is set to false. You provide no way of setting _isUsed, and so you're putting a check on a variable that a caller has no control over.

You could make _isUsed into a property i.e.

public bool IsUsed {get; set;}

And then in your SomeMethod() have

Contract.Requires(!IsUsed);