Tag Archives: Property

Property Copy in .Net

I came across a question on StackOverflow that asked how you can copy Properties from one class to the other assuming they had similar properties.

public class Student
{
    public int Id {get; set;}
    public string Name {get; set;}
    public IList<Course> Courses{ get; set;}
}

public class StudentDTO
{
    public int Id {get; set;}
    public string Name {get; set;}
    public IList<CourseDTO> Courses{ get; set;}
}

I would like to copy value from Student class to StudentDTO class:

var student = new Student();
StudentDTO studentDTO = student;

How can I do that by reflection or other solution?

The code someone posted on there linked to Miscellaneous Utility Library and that Property Copy was awesomely constructed. Have a gander at the result below and tell me it doesn’t blow your mind!!

using System;
using System.Collections;
using System.Collections.Specialized;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.ComponentModel;
using System.Linq.Expressions;

namespace ConsoleApplication1
{
    class Program
    {
        public class Student
        {
            public int Id { get; set; }
            public string Name { get; set; }
            public IList<int> Courses { get; set; }
            public static implicit operator Student(StudentDTO studentDTO)
            {
                return PropertyCopy<Student>.CopyFrom(studentDTO);
            }
        }

        public class StudentDTO
        {
            public int Id { get; set; }
            public string Name { get; set; }
            public IList<int> Courses { get; set; }
            public static implicit operator StudentDTO(Student student)
            {
                return PropertyCopy<StudentDTO>.CopyFrom(student);
            }
        }


        static void Main(string[] args)
        {
            Student _student = new Student();
            _student.Id = 1;
            _student.Name = "Timmmmmmmmaaaahhhh";
            _student.Courses = new List<int>();
            _student.Courses.Add(101);
            _student.Courses.Add(121);

            StudentDTO itemT = _student;

            Console.WriteLine(itemT.Id);
            Console.WriteLine(itemT.Name);
            Console.WriteLine(itemT.Courses.Count);
        }


    }


    // COOLEST PIECE OF CODE FROM - http://www.yoda.arachsys.com/csharp/miscutil/

    /// <summary>
    /// Generic class which copies to its target type from a source
    /// type specified in the Copy method. The types are specified
    /// separately to take advantage of type inference on generic
    /// method arguments.
    /// </summary>
    public class PropertyCopy<TTarget> where TTarget : class, new()
    {
        /// <summary>
        /// Copies all readable properties from the source to a new instance
        /// of TTarget.
        /// </summary>
        public static TTarget CopyFrom<TSource>(TSource source) where TSource : class
        {
            return PropertyCopier<TSource>.Copy(source);
        }

        /// <summary>
        /// Static class to efficiently store the compiled delegate which can
        /// do the copying. We need a bit of work to ensure that exceptions are
        /// appropriately propagated, as the exception is generated at type initialization
        /// time, but we wish it to be thrown as an ArgumentException.
        /// </summary>
        private static class PropertyCopier<TSource> where TSource : class
        {
            private static readonly Func<TSource, TTarget> copier;
            private static readonly Exception initializationException;

            internal static TTarget Copy(TSource source)
            {
                if (initializationException != null)
                {
                    throw initializationException;
                }
                if (source == null)
                {
                    throw new ArgumentNullException("source");
                }
                return copier(source);
            }

            static PropertyCopier()
            {
                try
                {
                    copier = BuildCopier();
                    initializationException = null;
                }
                catch (Exception e)
                {
                    copier = null;
                    initializationException = e;
                }
            }

            private static Func<TSource, TTarget> BuildCopier()
            {
                ParameterExpression sourceParameter = Expression.Parameter(typeof(TSource), "source");
                var bindings = new List<MemberBinding>();
                foreach (PropertyInfo sourceProperty in typeof(TSource).GetProperties())
                {
                    if (!sourceProperty.CanRead)
                    {
                        continue;
                    }
                    PropertyInfo targetProperty = typeof(TTarget).GetProperty(sourceProperty.Name);
                    if (targetProperty == null)
                    {
                        throw new ArgumentException("Property " + sourceProperty.Name + " is not present and accessible in " + typeof(TTarget).FullName);
                    }
                    if (!targetProperty.CanWrite)
                    {
                        throw new ArgumentException("Property " + sourceProperty.Name + " is not writable in " + typeof(TTarget).FullName);
                    }
                    if (!targetProperty.PropertyType.IsAssignableFrom(sourceProperty.PropertyType))
                    {
                        throw new ArgumentException("Property " + sourceProperty.Name + " has an incompatible type in " + typeof(TTarget).FullName);
                    }
                    bindings.Add(Expression.Bind(targetProperty, Expression.Property(sourceParameter, sourceProperty)));
                }
                Expression initializer = Expression.MemberInit(Expression.New(typeof(TTarget)), bindings);
                return Expression.Lambda<Func<TSource,TTarget>>(initializer, sourceParameter).Compile();
            }
        }
    }
}
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