Spring.net 调webservice 参数为空的异常

客户端： 

string saveString = GCE.Common.SerializerHelper.SerializeObject(dataList);
                    int nFlag = server.SaveData(saveString);

出错：

System.Web.Services.Protocols.SoapException: 服务器无法处理请求。 ---> System.NullReferenceException: 未将对象引用设置到对象的实例。

namespace IContract
{
    /// <summary>
    /// 考勤契约
    /// </summary>
    public interface IAttendanceContract
    {

               /// <summary>
        /// 保存数据
        /// </summary>
        /// <param name="sList">数据</param>
        /// <returns>1:成功;0失败</returns>
        int SaveData(string sList);
        /// <summary>
        /// 登出
        /// </summary>
            }
}

public class AttendanceContract : GCE.OA.IContract.IAttendanceContract
    {

                     private void CovertModel(GCE.OA.IContract.PMAttendanceTiming omodel, GCE.OA.Business.Model.PMAttendanceTiming model)
        {
                 }

        #region IAttendanceContract 成员
              /// <summary>
        /// 保存数据
        /// </summary>
        /// <param name="slist">数据</param>
        /// <returns>1:成功;0失败</returns>
        public int SaveData(string slist)
        {
                   }

               #endregion
    }

 string saveString = GCE.Common.SerializerHelper.SerializeObject(dataList);
                    int nFlag = server.SaveData(saveString);

原因是：参数大小写不一样，要一样的签名