Problem consuming Restful webservice. "Found conflicts between different versions of the same dep.."

Hi,

I am trying to get data from a Restful web service. I have followed the TodoREST sample. However when I build I get the warning: "Found conflicts between different versions of the same dependent assembly (MSB3247)." Could some one explain this warning?

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;  



namespace Lantern
{
    public class CharityDataRetriever
    {

        HttpClient client;

        public async Task<string> FindData (string iD)
        {
            string data = "";

            var uri = new Uri (iD);

            try {

                var response = await client.GetAsync(uri);

                if (response.IsSuccessStatusCode) {
                    var content = await response.Content.ReadAsStringAsync();
                    data = JsonConvert.DeserializeObject <string> (content);
                }

            } catch (Exception ex) {
                Debug.WriteLine(@"     ERROR {0}", ex.Message);
            }


            return data;

        }

    }
}