using System;

using System.Linq.Expressions;

using System.Reflection;

public class Program

{

    public static void Main()

    {

        var orderDto = new OrderDto

        {

            Id = 1,

            Name = "Name",

            CreatedOn = DateTime.UtcNow,

            CompletedOn = DateTime.UtcNow.AddMinutes(30),

            Misc = Guid.NewGuid()

        };

​

        Console.WriteLine($"{orderDto.Id} {orderDto.Name} {orderDto.CreatedOn} {orderDto.CompletedOn} {orderDto.Misc}");

        orderDto.DefaultFor(x => x.Id, x => x.Name, x => x.CreatedOn, x => x.CompletedOn);

​

        Console.WriteLine($"{orderDto.Id} {orderDto.Name} {orderDto.CreatedOn} {orderDto.CompletedOn} {orderDto.Misc}");

    }

}

​

public static class ObjectExtensions

{

    public static void DefaultFor<TObject, TProp1, TProp2, TProp3, TProp4>(this TObject instance, 

        Expression<Func<TObject, TProp1>> selector1, 

        Expression<Func<TObject, TProp2>> selector2,

        Expression<Func<TObject, TProp3>> selector3,

        Expression<Func<TObject, TProp4>> selector4)

        where TObject : class

    {

        DefaultFor(instance, selector1, selector2, selector3);

        DefaultFor(instance, selector4);

    }

​

    public static void DefaultFor<TObject, TProp1, TProp2, TProp3>(this TObject instance, 

        Expression<Func<TObject, TProp1>> selector1, 

        Expression<Func<TObject, TProp2>> selector2,

        Expression<Func<TObject, TProp3>> selector3)

        where TObject : class

    {

        DefaultFor(instance, selector1, selector2);

        DefaultFor(instance, selector3);

    }

​

    public static void DefaultFor<TObject, TProp1, TProp2>(this TObject instance, 

        Expression<Func<TObject, TProp1>> selector1, 

        Expression<Func<TObject, TProp2>> selector2)

        where TObject : class

    {

        DefaultFor(instance, selector1);

        DefaultFor(instance, selector2);

    }

    public static void DefaultFor<TObject, TProp>(this TObject instance, Expression<Func<TObject, TProp>> selector)

        where TObject : class

    {

        if (instance == null)

            throw new ArgumentNullException();

​

        var memberExpression = (MemberExpression)selector.Body;

        var property = (PropertyInfo)memberExpression.Member;

​

        property.SetValue(instance, default(TProp));

    }

}

​

public class OrderDto

{

    public int Id { get; set; }

    public string Name { get; set; }

    public DateTime CreatedOn { get; set; }

    public DateTime? CompletedOn { get; set; }

    public Guid Misc { get; set; }

}