(C#) 인스턴스는 Expression Tree를 사용하여 동적으로 생성됩니다.

Expression Tree 소개

람다식 Expression Tree 제작

Expression<Func<int, int>> exp = x => x + 5; 

// 引数x の式
var arg = Expression.Parameter(typeof(int), "x");
// x + 5の式
var body = Expression.Add(x, Expression.Constant(5));
// x => x + 5の式
var exp = Expression.Lambda<Func<int, int>>(body, x);

Expression Tree를 사용하여 인스턴스 생성

public static class InstanceCreator<T>
{
    /// <summary>
    /// T型のインスタンスを生成します
    /// </summary>
    public static Func<T> Create => CreateInstance();
    public static Func<T> CreateInstance()
    {
        return Expression.Lambda<Func<T>>(Expression.New(typeof(T))).Compile();
    }
}

public class Person { }
public class Test
{
  public void InstanceCreateTest()
  {
      var person = new Person();
      var expressionPerson = InstanceCreator<Person>.Create();
  }
}

public static class InstanceCreator<TParam, TInstance>
{
    /// <summary>
    /// 一つの引数を受け取ってTInstance型のインスタンスを生成します
    /// </summary>
    public static Func<TParam, TInstance> Create => CreateInstance();
    public static Func<TParam, TInstance> CreateInstance()
    {
        var argsType = new[] { typeof(TParam) };
        var constructor = typeof(TInstance).GetConstructor(argsType);
        var args = argsType.Select(Expression.Parameter).ToList();
        return Expression.Lambda<Func<TParam, TInstance>>(Expression.New(constructor, args), args).Compile();
    }
}