Mapping base classes solution without losing non-nullable reference types | C# Online Compiler

Mapping base classes solution without losing non-nullable reference types by JoepGeevers

using System;

public class Program
{
	static void Main()
	{
		MapFrom(new RequestV1
		{
			Name = "Joep Geevers",
			BornAt = new DateTime(1976, 11, 26, 9, 17, 0),
		}).Dump();
		
		MapFrom(new RequestV2
		{
			FirstName = "Joep",
			LastName = "Geevers",
			BornAt = new DateTime(1976, 11, 26, 9, 17, 0),
		}).Dump();
	}

	private static PersonRecord MapFrom(RequestV1 source)
		=> MapFrom( 										// ask the generic mapper to create the PersonRecord first, so it's properties can be non-nullable reference types
			source,
			(source, target) => target.Name = source.Name); // then apply the specific mapping logic

	private static PersonRecord MapFrom(RequestV2 source)
		=> MapFrom(
			source,
			(source, target) => target.Name = $"{source.FirstName} {source.LastName}");

	private static PersonRecord MapFrom<T>(T source, Action<T, PersonRecord> mapper)
		where T : RequestBase
		{
			var target = new PersonRecord
			{
				BornAt = source.BornAt,
			};

			mapper(source, target);

			return target;
		}
}

public class RequestV1 : RequestBase
{
	public string Name { get; set; }
}

public class RequestV2 : RequestBase
{
	public string FirstName { get; set; }

	public string LastName { get; set; }
}

public abstract class RequestBase
{
	public DateTime BornAt { get; set; }
}

public class PersonRecord
{
	public string Name { get; set; }

	public DateTime BornAt { get; set; }
}

​x
 
using System;
​
public class Program
{
    static void Main()
    {
        MapFrom(new RequestV1
        {
            Name = "Joep Geevers",
            BornAt = new DateTime(1976, 11, 26, 9, 17, 0),
        }).Dump();
        
        MapFrom(new RequestV2
        {
            FirstName = "Joep",
            LastName = "Geevers",
            BornAt = new DateTime(1976, 11, 26, 9, 17, 0),
        }).Dump();
    }
​
    private static PersonRecord MapFrom(RequestV1 source)
        => MapFrom(                                         // ask the generic mapper to create the PersonRecord first, so it's properties can be non-nullable reference types
            source,
            (source, target) => target.Name = source.Name); // then apply the specific mapping logic
​
    private static PersonRecord MapFrom(RequestV2 source)
        => MapFrom(
            source,
            (source, target) => target.Name = $"{source.FirstName} {source.LastName}");
​
    private static PersonRecord MapFrom<T>(T source, Action<T, PersonRecord> mapper)
        where T : RequestBase
        {
            var target = new PersonRecord
            {
                BornAt = source.BornAt,
            };
​
            mapper(source, target);
​
            return target;
        }
}
​
public class RequestV1 : RequestBase
{
    public string Name { get; set; }
}
​
public class RequestV2 : RequestBase
{
    public string FirstName { get; set; }
​
    public string LastName { get; set; }
}
​
public abstract class RequestBase
{
    public DateTime BornAt { get; set; }
}
​
public class PersonRecord
{
    public string Name { get; set; }
​
    public DateTime BornAt { get; set; }
}

Compilation error (line 19, col 15): 'Student.PrintInfo()' hides inherited member 'Human.PrintInfo()'. Use the new keyword if hiding was intended.
Compilation error (line 33, col 4): Cannot access protected member 'A.y' via a qualifier of type 'A'; the qualifier must be of type 'Program' (or derived from it)
Compilation error (line 34, col 4): 'A.z' is inaccessible due to its protection level
Compilation error (line 38, col 5): 'A.z' is inaccessible due to its protection level

Last Run:	4:38:14 am
Compile:	0s
Execute:	0.173s
Memory:	0b
CPU:	0s

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