I would suggest using System.Runtime.Serialization.Json
that is part of .NET 4.5.
[DataContract]
public class Foo
{
[DataMember(Name = "data")]
public Dictionary<string,string> Data { get; set; }
}
Then use it like this:
var serializer = new DataContractJsonSerializer(typeof(List<Foo>));
var jsonParams = @"{""data"": [{""Key"":""foo"",""Value"":""bar""}] }";
var stream = new MemoryStream(Encoding.UTF8.GetBytes(jsonParams));
var obj = serializer.ReadObject(stream);
Console.WriteLine(obj);