What does the “private” modifier do?

Question

Considering \"private\" is the default access modifier for class Members, why is the keyword even needed?

Answer 1

Using private explicitly signals your intention and leaves clues for others who will support your code ;)

Answer 2

Actually, if the class or struct is not declared with an access modifier it defaults to internal.

So if you want to make it private, use private.

Answer 3

As pointed out by Jon Skeet in his book C# In Depth, there is one place in C# where the private keyword is required to achieve an effect.

If my memory serves correctly, the private keyword is the only way to create a privately scoped property getter or setter, when its opposite has greater than private accessibility. Example:

public bool CanAccessTheMissileCodes
{
    get { return canAccessTheMissileCodes; }
    private set { canAccessTheMissileCodes = value; }
}

The private keyword is required to achieve this, because an additional property accessability modifier can only narrow the scope, not widen it. (Otherwise, one might have been able to create a private (by default) property and then add a public modifier.)

Answer 4

Some coding styles recommend that you put all the "public" items first, followed by the "private" items. Without a "private" keyword, you couldn't do it that way around.

Update: I didn't notice the "c#" tag on this so my answer applies more to C++ than to C#.

Answer 5

The private modifier explains intent.

A private member variable is not intended for direct manipulation outside the class. get/set accessors may or may not be created for the variable.

A private method is not intended for use outside the class. This may be for internal functionality only. Or you could make a default constructor private to prevent the construction of the class without passing in values.

The private modifier (and others like it) can be a useful way of writing self documenting code.

Answer 6

For completenes. And some people actually prefer to be explicit in their code about the access modifiers on their methods.