c# - Entity Framework The underlying provider failed on Open -

below connection string:

connectionstring="metadata=res://*/edmx.test.csdl|res://*/edmx.test.ssdl|res://*/edmx.test.msl;provider=system.data.sqlclient;provider connection string="data source=home_computer;initial catalog=db_test;persist security info=true;user id=testuser;password=$1234;multipleactiveresultsets=true""

here code program stuck:

edmx.testingentity context = new edmx.testingentity();  var query = t in context.user             t.username == _username             select t; 

after running above code, check variable query , found exception

the underlying provider failed on open.

i've checked:

1. connection between server , computer normal
2. i can login database username testuser , password $1234
3. i have checked security settings in database (sql server) permission has been granted testuser

why exception happen? i'm using .net 4.5

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added:

i tried again, @ inner exception , was: network-related or instance-specific error occurred while establishing connection sql server. server not found or not accessible. verify instance name correct , sql server configured allow remote connections. (provider: named pipes provider, error: 40 - not open connection sql server)

i know might network problem i've turned off firewall of server , computer , tried again still not success..

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just copied connectionstring program test connection , functioning well..

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i rollback changes , test again , worked

seems connection issue. can use data link properties find if connection fine. following:

1. create blank notepad , rename "x.udl"
2. double click open it
3. under connections tab choose server name/enter name use correct credentials , db
4. click ok save it.

now open file in notepad , compare connection string properties.