My LimitedString with implicit cast to string

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
  class Program
  {
    static void Main(string[] args)
    {
      var ls = LimitedString.Create(5);

      ls.Value = "12345";

      Console.WriteLine(ls);

      var str = ls;
      Console.WriteLine(str);

      try
      {
        ls.Value = "123456";

        Console.WriteLine("Fail");
      }
      catch (ArgumentException ex)
      {
        Console.WriteLine("Success");
        Console.WriteLine(ex.Message);
      }
    }
  }

  class LimitedString
  {
    private uint _length;

    private LimitedString(uint length)
    {
      this._length = length;
    }

    public static LimitedString Create(uint length)
    {
      return new LimitedString(length);
    }

    private string _value;
    public string Value
    {
      get
      {
        return _value;
      }
      set
      {
        if ((value ?? "").Length > _length)
        {
          throw new ArgumentException(
            String.Format("入力文字列の長さが{0}を超えています", this._length)
            );
        }
        this._value = value;
      }
    }

    public override string ToString()
    {
      return this._value;
    }

    public static implicit operator string(LimitedString ls)
    {
      return ls._value;
    }
  }
}