SQLSERVER：Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

1、Max Pool Size 默认为100。

2、查看当前数据库连接数量，

select * from sysprocesses where dbid= db_id('数据库名称')

结果为190，

3、添加数据库查询的最大连接数量

Data Source=.;Initial Catalog=i_Master;Persist Security Info=True;User ID=NUser;Password=N2;max pool size=500
设置最大连接数量 500