WCF动态响应格式

如何使用查询字符串创建动态响应?

我想根据用户在消息体中指定的内容动态输出响应格式。

例如，如果用户输入"json"，"xml"，"soap"，它将返回各自的格式。谢谢，提前说。

public interface IReg
{
    [OperationContract]
    [WebInvoke]
    MemberBasic Login(string uniqueID, string password, string returnFormat);
}
[DataContract(Namespace = "", IsReference=false)]
[Serializable()]
public class MemberBasic
{
    #region Properties
    [DataMember]
    public DateTime LastModified
    {
        get;
        set; 
    }
}
 [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
public sealed class RWS : IReg
{

    public MemberBasic Login(string uniqueID, string password, string returnFormat)
    {
        MemberBasic result = new MemberBasic();
        setReturnFormat(returnFormat);
        return result;
    }
}
private static void Init(string returnFormat)
    {
        var response = WebOperationContext.Current.OutgoingResponse;
        response.Headers.Add("cache-Control", "no-cache");
        response.Headers.Add("Last-Modified", string.Format("{0:r}", DateTime.Today));
        switch (returnFormat)
        {
            case "xml":
                {
                    WebOperationContext.Current.OutgoingResponse.Format = WebMessageFormat.Xml;
                    WebOperationContext.Current.OutgoingRequest.Headers.Add(System.Net.HttpRequestHeader.ContentType, "application/json");
                } break;
            case "json":
                {
                    WebOperationContext.Current.OutgoingResponse.Format = WebMessageFormat.Json;
                } break;
            default:
                {
                    throw new ArgumentException("Return Format unrecognized; cannot complete request.",
                        "returnFormat");
                }
        }
    }