C# Expression Paths

Program.cs

using System.Linq.Expressions;

List<string> MemberNames(Expression<Func<User, object>> u)
{
    return ExpressionReader.GetNestedMemberNames(u);
}

Console.WriteLine(string.Join(".", MemberNames(u => u.UserProfile.HomeAddress.City)));

public class User
{
    public int Id { get; set; }
    public Profile UserProfile { get; set; }

    public class Profile
    {
        public Address HomeAddress { get; set; }
    }

    public class Address
    {
        public string City { get; set; }
    }
}

public static class ExpressionReader
{
    public static List<string> GetNestedMemberNames<T, TValue>(
        Expression<Func<T, TValue>> expression
    )
    {
        var memberNames = new List<string>();
        MemberExpression? memberExpression;

        // Check if the expression is a UnaryExpression for boxing
        if (
            expression.Body is UnaryExpression unaryExpression
            && unaryExpression.Operand is MemberExpression unaryMember
        )
        {
            memberExpression = unaryMember;
        }
        else if (expression.Body is MemberExpression member)
        {
            memberExpression = member;
        }
        else
        {
            throw new ArgumentException(
                "Expression body must be a MemberExpression.",
                nameof(expression)
            );
        }

        // Walk the tree from the deepest member up to the root
        while (memberExpression != null)
        {
            memberNames.Add(memberExpression.Member.Name);
            memberExpression = memberExpression.Expression as MemberExpression;
        }

        // Reverse the list to get the correct order (e.g., "UserProfile.HomeAddress.City")
        memberNames.Reverse();
        return memberNames;
    }
}