我無法從Google搜索中獲得明確的指導。我有一個名為的表transaction，我想針對外鍵進行分組BatchID和排序descending。表定義[TTransactionID] INT IDENTITY (1, 1) NOT NULL,[BatchID] INT NULL,[CardID] INT NULL,[UserID] INT NULL,[TransactionDateTime] DATETIME NOT NULL,[TransactionStatus] VARCHAR (11) NOT NULL,CONSTRAINT [PK_Transactions] PRIMARY KEY CLUSTERED ([TTransactionID] ASC),CONSTRAINT [FK_Transactions_Cards] FOREIGN KEY ([CardID]) REFERENCES [dbo].[Cards] ([CardID]),CONSTRAINT [FK_Transactions_Users] FOREIGN KEY ([UserID]) REFERENCES [dbo].[Users] ([UserID]) NOT FOR REPLICATION這是我第五次嘗試的代碼 var TransactionList = db.Transactions .GroupBy(x => new { x.BatchID }) .Select(x => x.ToList()).ToList(); int index = 0; foreach (var item in TransactionList) { Response.Write( string.Format("[{0}] - {1}", index, item) ); index++; }當我運行上面的代碼時。我在瀏覽器上收到以下消息。我被困在這里，之后我不知道該怎么辦。System.Collections.Generic.List`1[SECardDistribution.Models.Transaction]請告知謝謝
3 回答
一只名叫tom的貓
TA貢獻1906條經驗 獲得超3個贊
請注意，TransationList按BatchId升序排序，然后按CardId降序排序。
var TransactionList = context.Trx
.GroupBy(t => t.BatchId) //group by BatchId
.OrderBy(t => t.Key) //order by BatchId
.Select
(g =>
//Create a new "Batch Group" anonymously where each batch contains the associated transactions
new
{
BatchId = g.Key,
BatchTransactions = g.Select(trx => new { Card = trx.Card, User = trx.User }).OrderByDescending(batchTrx => batchTrx.Card.CardId), //order by CardId
}
);
要遍歷排序列表，可以使用嵌套的foreach循環，如下所示：
//Loop through the batch group in the sorted list
foreach(var batchGroup in TransactionList)
{
foreach(var batchTrx in batchGroup.BatchTransactions)
{
//You may access the properties of batchTrx like a normal object graph, example batchTrx.Card.CardId
}
}
海綿寶寶撒
TA貢獻1809條經驗 獲得超8個贊
你可以SelectMany實際使用
var transactionList = db.Transactions.GroupBy(x => new { x.BatchID }).SelectMany(x => x).ToList();
慕俠2389804
TA貢獻1719條經驗 獲得超6個贊
// doing Select(x => x.ToList()) throws away group key!
var TransactionList = db.Transactions.GroupBy(x => x.BatchID).ToList();
foreach (var group in TransactionList)
{
// now group variable is a ... well, group of transactions. :)
// you can get its key and iterate over sub-collection of transactions in this group.
Response.Write($"Group {group.Key}:\n");
foreach (var item in group)
{
Response.Write($" Transaction {item.TTransactionID}\n");
}
}
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