使用ViewFields提升SPQuery查询性能

        用SPquery查询文档库文件，当使用了Scope=\"Recursive\后，性能大幅下降，通过开发人员面板看到我的webpart查询数据耗时：EnsureListItemsData (196.45 ms)

       在查询语句中加入ViewFields限制，只取需要用到的字段，查询时间能缩短将近一半：EnsureListItemsData (96.47 ms)

sPQuery.ViewFields = string.Concat(
                   "<FieldRef Name='FileLeafRef' />",
                   "<FieldRef Name='EncodedAbsUrl' />",
                   "<FieldRef Name='Modified' />",
                   "<FieldRef Name='File_x0020_Type' />",
                   "<FieldRef Name='LinkTitle' />",
                   "<FieldRef Name='ServerUrl' />",
                   "<FieldRef Name='PermMask' />");
sPQuery.ViewFieldsOnly = true;