传递WCF数据成员失败

问题:WCF数据合约类中的部分(但不是全部)数据成员无法正常传递。

[ServiceContract]
public interface ICheckList
{
    [OperationContract]
    int UpsertManager(ManagerEntity newObj);
}
[DataContract]
[Serializable]
public class ManagerEntity
{
    [DataMember] public bool TrainingComplete{get;set;}
    [DataMember] public int IsPosted{get;set;}
    [DataMember] public DateTime TrainingDate{get;set;}
    [DataMember] public string Comments{get;set;}
}

客户端代码:

BRTWSLChecklist.ManagerEntity newModel = new BRTWSLChecklist.ManagerEntity();
newModel.TrainingComplete = model.HasTrainingDate;
newModel.Comments = model.Comments;
newModel.IsPosted = 1;
newModel.TrainingDate = DateTime.Today;
ChecklistClient.UpsertManager(newModel);

WCF的一面:

public int UpsertManager(ManagerEntity newObj)
{
    bool t = newObj.TrainingComplete;   //always false
    DateTime x = newObj.TrainingDate;   //always equal to 1/1/0001
    string c = newObj.Comments;         //no problems here 
    int d = newObj.IsPosted;            //no problems here
}

你知道为什么四分之二是可以的，但日期和时间是失败的吗??