[ARROW-7757] [C#] Change the class access modifier of `PrimitiveArrayBuilder` to public

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.15.1
• Component/s: C#
• External issue URL: https://github.com/apache/arrow/issues/23995
• Assignee: Unassigned
• Reporter: Zachary Gramana
• Created: 03/Feb/20 23:05
• Updated: 11/Jan/23 07:55

Description

Currently, a user seeking to add a `Builder<T>` class to their user-defined type in C# can subclass `PrimitiveArrayBuilder` since it is marked `public abstract`. However, it's parameterless constructor is marked as `internal` making it impossible to compile the user's class.

The preferred solution would be to mark this constructor as `public`. If this cannot be done for some reason, the entire `PrimitiveArrayBuilder` class should be marked `internal` to avoid confusion.