认为我需要做的是更新WAMS记录是选择我想要的记录,然后修改我要更改的所选记录的成员,最后在该记录上调用Update,我有这个代码:
public static async Task<bool> UpdateInvitation(string senderID, string readerName, string senderDeviceID)
{
try
{
IMobileServiceTable<WAMS_INVITATIONS> invitationsTable = App.MobileService.GetTable<WAMS_INVITATIONS>();
MobileServiceTableQuery<WAMS_INVITATIONS> invitationRecordToUpdate =
invitationsTable.Where(i => i.SenderID == senderID).
Where(i => i.ReaderName == readerName).
//Select(i => i.SenderDeviceID).
Take(1); // the query returns a List, but I only want 1 record (and it should only return 1)
//invitationRecordToUpdate.SenderDeviceID = senderDeviceID; <-- "SenderDeviceID" not recognized
await invitationsTable.UpdateAsync(invitationRecordToUpdate);
}
catch (Exception)
{
return false;
}
return true; // If no exception, assume record was inserted successfully
}
...但它甚至不会编译。我得到的错误信息是:
1) *最佳重载方法匹配'Microsoft.WindowsAzure.MobileServices.IMobileServiceTable.Upd ateAsync(PhoneApp.Data.WAMS_INVITATIONS)'有一些无效的参数*
......好吧,但是无效的论点是什么?
2) *参数1:无法转换 “Microsoft.WindowsAzure.MobileServices.MobileServiceTableQuery
'到'PhoneApp.Data.WAMS_INVITATIONS'“*
我希望invitationRecordToUpdate包含WAMS_INVITATIONS的所有成员/列, 包括SenderDeviceID,但没有......为什么?更重要的是,什么是规范/首选方法 (没有双关语)更新WAMS记录?
(没有双关语意,虽然这个问题的确围绕着更新)
尝试使用建议的答案,这不会'编译:
invitationsTable.Where(i => i.SenderID == senderID && i.ReaderName == readerName).SingleOrDefault
();
(在VS编辑器中,“SingleOrDefault”比毛主席的书更红)
......而且这个:
await invitationsTable.UpdateAsync(invitationRecordToUpdate[0]);
...也无法计算,但是:“无法将带有[]的索引应用于类型为”Microsoft.WindowsAzure.MobileServices.MobileServiceTableQuery“的表达式”
将其改为:
IMobileServiceTable<TASLS_WAMS_INVITATIONS> invitationsTable = App.MobileService.GetTable<TASLS_WAMS_INVITATIONS>();
......对此:
var invitationsTable = App.MobileService.GetTable<TASLS_WAMS_INVITATIONS>();
...没有区别(它不应该 - 所有这一切都是根据类型的构造函数隐式显式数据类型。
所以我的代码现在是:
public static async Task<bool> UpdateInvitation(string senderID, string readerName, string senderDeviceID)
{
try
{
IMobileServiceTable<TASLS_WAMS_INVITATIONS> invitationsTable = App.MobileService.GetTable<TASLS_WAMS_INVITATIONS>();
MobileServiceTableQuery<TASLS_WAMS_INVITATIONS> invitationRecordToUpdate =
invitationsTable.Where(i => i.SenderID == senderID).
Where(i => i.ReaderName == readerName).
Take(1);
if (null != invitationRecordToUpdate)
{
//await invitationsTable.UpdateAsync(invitationRecordToUpdate[0]); //both of these fail...
//await invitationsTable.UpdateAsync(invitationRecordToUpdate);
}
}
catch (Exception)
{
return false;
}
return true; // If no exception, assume record was inserted successfully
}
...正如您所看到的,我无法使用UpdateAsync,因为这两种方式(注释掉)都不会编译。
答案 0 :(得分:1)
当返回列表只使用第一个元素时:
await invitationsTable.UpdateAsync(invitationRecordToUpdate[0]);
你可以做出更好的linq:
invitationsTable.Where(i => i.SenderID == senderID && i.ReaderName == readerName).SingleOrDefault();
记得chek项目存在:
if(invitationRecordToUpdate!=null)
{//UPDATE }
SingleOrDefault方法:
返回序列的唯一元素,如果序列为空,则返回默认值;如果序列中有多个元素,则此方法抛出异常。
答案 1 :(得分:1)
像这样更新并显示错误:
public static async Task<bool> UpdateInvitation(string senderID, string readerName, string senderDeviceID)
{
try
{
IMobileServiceTable<TASLS_WAMS_INVITATIONS> invitationsTable = App.MobileService.GetTable<TASLS_WAMS_INVITATIONS>();
var invitationRecordToUpdate =
invitationsTable.Where(i => i.SenderID == senderID).
Where(i => i.ReaderName == readerName).
Take(1).ToListAsync();
await invitationsTable.UpdateAsync(invitationRecordToUpdate[0]);
}
catch (Exception)
{
return false;
}
return true; // If no exception, assume record was inserted successfully
}
EDIT 我刚检查了我的Windows Stre应用程序。我用这个,一切都很好:
private IMobileServiceTable<Rating> RatingTable =
App.MobileService.GetTable<Rating>();
var list = await RatingTable.Where(p => p.Id == sel_item.Id && p.User == user).ToListAsync();
vat item=list[0];