Using Hashtable in WCF

Scenario:
I wanted to store some key value pair information in my DataMember. I thought of using Hashtable as DataMember, so far so good but when adding the service reference from my client application, I noticed that Hashtable got converted to Dictionary and while compiling I got the following error

Cannot implicitly convert type 'System.Collections.Generic.Dictionary' to 'System.Collections.Hashtable'

Workaround:
The representation of a Hashtable in the wire is equivalent to the representation of a dictionary. So it will just work if you use the Dictionary at the client side

Solution:
Right click the Service reference > Configure Service Reference > Select 'System.Collection.Hashtable' from Dictionary collection type drop down menu.

But i wanted to still use Hashtable, so this is how i did it.
Here's the code.

IService1.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

using System.Collections;

namespace TestWCF
{
   [ServiceContract]
   public interface IService1
   {
       [OperationContract]
       CompositeType GetDataUsingDataContract(CompositeType composite);
  }

  [DataContract]
   public class CompositeType
   {
       private Hashtable doc;
       [DataMember]
       public Hashtable Doc
       {
           get { return doc; }
           set { doc = value; }
       }
   }
}

Service1.cs:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

namespace TestWCF
{
   public class Service1 : IService1
   {
       public CompositeType GetDataUsingDataContract(CompositeType composite)
       {
         composite.Doc = new Hashtable();
         composite.Doc.Add("A","B");

           return composite;
       }
   }
}

I created a Windows Form application to test the WCF service.
Form1.cs:

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace TestWCFClient
{
   public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
       }

       private void Form1_Load(object sender, EventArgs e)
       {
           ServiceReference1.CompositeType composite = new ServiceReference1.CompositeType() ;
           ServiceReference1.CompositeType composite2 = new ServiceReference1.CompositeType() ;

           ServiceReference1.Service1Client sc = new ServiceReference1.Service1Client();
           composite2 = sc.GetDataUsingDataContract(composite);
           MessageBox.Show(composite2.Doc["A"].ToString());
       }
   }
}