Nested types should not be visible
Nested types should not be visible
Microsoft docsDescription
A nested type is a type declared within the scope of another type. Nested types are useful for encapsulating private implementation details of the containing type. Used for this purpose, nested types should not be externally visible.
Do not use externally visible nested types for logical grouping or to avoid name collisions; instead, use namespaces.
Nested types include the notion of member accessibility, which some programmers do not understand clearly.
Protected types can be used in subclasses and nested types in advance customization scenarios.
Cause
An externally visible type contains an externally visible type declaration. Nested enumerations, protected types, and builder patterns are exempt from this rule.
How to fix violations
If you do not intend the nested type to be externally visible, change the type's accessibility. Otherwise, remove the nested type from its parent. If the purpose of the nesting is to categorize the nested type, use a namespace to create the hierarchy instead.
Example
public class ParentType
{
public class NestedType
{
public NestedType()
{
}
}
public ParentType()
{
NestedType nt = new NestedType();
}
}When to suppress
Do not suppress a warning from this rule.