CA1012Design Enabled by default: No

Abstract types should not have public constructors

Description

Constructors on abstract types can be called only by derived types. Because public constructors create instances of a type, and you cannot create instances of an abstract type, an abstract type that has a public constructor is incorrectly designed.

Cause

A type is abstract and has a public constructor.

By default, this rule only looks at externally visible types, but this is configurable.

How to fix violations

To fix a violation of this rule, either make the constructor protected or don't declare the type as abstract.

Example

// Violates this rule
public abstract class Book
{
    public Book()
    {
    }
}

// Does not violate this rule
public abstract class Book
{
    protected Book()
    {
    }
}

When to suppress

Do not suppress a warning from this rule. The abstract type has a public constructor.

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