Timeout expired. The timeout period elapsed prior to complet

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

问题：

最近程序总会抛出如下异常：

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)......

读取数据超时。

然后就去看了下DataBase里对应的tables，发现table的结构简单，但是数据量很大，有几十万上百万条。再看一下有没有建Indexes/Keys，发现没有，恍然大悟。

解决方法：

根据表的结构，建立了Indexes/Keys下的 Unique key，类似如下：

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

测试，发现速度快很多，减小了timeout的风险。