Timeout expired. The timeout period elapsed prior to completion of the operation or the server...，elapsedserver..

Timeout expired. The timeout period elapsed prior to completion of the operation or the server...，elapsedserver..

問題：

最近程式總會拋出如下異常：

An exception of type'System.Data.SqlClient.SqlException' occurred and was caught.

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Type :System.Data.SqlClient.SqlException, System.Data, Version=4.0.0.0,Culture=neutral, PublicKeyToken=b77a5c561934e089

 Message : Timeoutexpired.  The timeout period elapsedprior to completion of the operation or the server is not responding.

Source : .Net SqlClient Data Provider......

......Database.ExecuteReader(DbCommandcommand)......

讀取資料逾時。

然後就去看了下DataBase裡對應的tables，發現table的結構簡單，但是資料量很大，有幾十萬上百萬條。再看一下有沒有建Indexes/Keys，發現沒有，恍然大悟。

解決方案：

根據表的結構，建立了Indexes/Keys下的 Unique key，類似如下：

ALTER TABLE [dbo].[ZData] add  CONSTRAINT [IX_ZData] UNIQUE NONCLUSTERED ([Pid] ASC,[EntryID] ASC,[Date] ASC)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]GO

測試，發現速度快很多，減小了timeout的風險。