WebAPI指定更新字段问题

想通过WebAPI更新物料盘点作业盘点数量（只更新盘点数量），在NeedUpdateFields，WebAPI返回成功了，但是字段值并没有更新
[code]{
"Creator": "xuyonggang",
"NeedUpDateFields": [
"FCountQty"
],
"Model": {
"FID": 100009,
"STK_StockCountInput__FBillEntry": [
{
"FStockId": {
"FNumber": "001"
},
"FMaterialId": {
"FNUMBER": "YL0001"
},
"FLot": {
"FNumber": "20160930"
},
"FCountQty": 10
},
{
"FStockId": {
"FNumber": "001"
},
"FMaterialId": {
"FNUMBER": "YL0002"
},
"FLot": {
"FNumber": "20160930"
},
"FCountQty": 10
}
]
}
}[/code][code]{"Result":{"ResponseStatus":{"IsSuccess":true,"Errors":[],"SuccessEntitys":[{"Id":100009,"Number":"PDZY000005","DIndex":0}],"SuccessMessages":[]},"Id":100009,"Number":"PDZY000005"}}[/code]