Entity Framework The underlying provider failed on Open

Question

Below is my connection string      connectionString  metadata res     EDMX Test csdl res     EDMX Test ssdl res     EDMX Test msl provider System Data SqlClient provider   connection string  quot Data Source home computer Initial   Catalog db Test Persist Security Info True User   ID testUser Password  1234 MultipleActiveResultSets True quot     Here is the code where the program stuck   EDMX TestingEntity context   new EDMX TestingEntity     var query   from t in context User             where t UserName     userName             select t    After running the above code  I check the variable query and found an exception      The underlying provider failed on Open    I ve checked    Connection between server and computer is normal    I can login to the database with username testuser and with password  1234    I have checked the security settings in database  SQL Server  that permission has been granted to testUser   Why does this exception happen  I m using  net 4 5    Added   I tried again  look at the inner exception and it was  A network-related or instance-specific error occurred while establishing a connection to SQL Server  The server was not found or was not accessible  Verify that the instance name is correct and that SQL Server is configured to allow remote connections   provider  Named Pipes Provider  error  40 - Could not open a connection to SQL Server   I know it might be a network problem but I ve turned off the firewall of server and also my computer and tried again but still not success      Just now Copied the connectionstring to a program to test this connection and it was functioning well      I just rollback all changes and test again and it worked

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Please check the following things first   While generating the Edmx you would have given a name to you connection string  that gets into the app config of the project with the Entity   Have you copied the same connection string to your main Config file  Also the Name should be same as which you have given while generating the EDMX file

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I had this error and it was caused by a typo in the connection string in App config

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open SQL Server Configuration Manager then click on sql server services a list will  be displayed from the list right click sql server and click on start

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I saw this error when a colleague was trying to connect to a database that was protected behind a VPN   The user had unknownling switched to a wireless network that did not have VPN access   One way to test this scenario is to see if you can establish a connection in another means  such as SSMS  and see if that fails as well

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This solution is for someone facing this issue while deploying a windows application  I know this is late  but this maybe useful for someone in future  In my scenario  purely this is a connection string issue I developed a windows application using entity framework  DB First approach  and I published it  the code was worked fine on my machine  but it s not worked on the client machine Reason for this issue - I updated the client machine connection string in App config file  but this is wrong  if that is a windows application  then it will not read the connection string from App config  For deployed machines   it will read from  exe config file  So after deployment  we need to change the connection string in  quot AppicationName quot  exe config file

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Try this- Open the command prompt as administrator and type this netsh Winsock reset  Restart your system and try again

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For me when that usually starts happening  I have to remote desktop into the service and at the minimum restart IIS  It usually starts popping up right after I deploy code  On a few rare occasions I have had to restart the SQL services and IIS  I wrote a batch script to take a param  1 or 2  and have it setup to either do a restart of IIS   i e  1   or go full nuclear  i e  2

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I was facing the same error today  what I was doing wrong was that I was not adding Password tag in the connection string  As soon as I added the Password tag with correct password the error went away  Hope it helps someone

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I faced the same issue  Though in my case I was trying to connect my desktop application to a remote db  So for me  all the above didn t work  I solve this problem by just adding the port  as 128 02 39 29 3315  and it magically works  The reason why I didn t bother to add the port in the first place is because I used same approach  without the port  in another desktop app and it worked  So I hope this might help someone as well

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Search  Component Services  in Programs and Files Go to Services Find  Distributed Transaction Coordinator  Service Right click and Restart the Service   You ve just done a restart of the service and the code should run without errors

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We had connection string in web config with Data Source localhost  and there was this error  MSSQL was on the same machine   Changing it to actual  DOMAIN MACHINE  helped  somewhy

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I get this exception often while running on my development machine  especially after I make a code change  rebuild the code  then execute an associated web page s    However  the problem goes away for me if I bump up the CommandTimeout parameter to 120 seconds or more  e g   set context Database CommandTimeout   120 before the LINQ statement    While this was originally asked 3 years ago  it may help someone looking for an answer   My theory is VisualStudio takes time to convert the built binary libraries to machine code  and times out when attempting to connect to SQL Server following that just-in-time compile

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Always check for Inner Exception if any  In my case Inner Exception turned out to be really helpful in figuring out the issue   My site was working fine in Dev Environment  But after i deployed to production  it started giving out this exception  but the Inner Exception was saying that Login failed for the particular user  So i figured out it was something to do with the connection itself  Hence tried logging in using SSMS and even that failed   Eventually figured out that exception showed up for the simple reason that the SQL server had only Windows Authentication enabled and SQL Authentication was failing which was what i was using for Authentication    In short  changing Authentication to Mixed SQL and Windows   fixed the issue for me

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ERROR   An exception of type  System Data Entity Core EntityException    occurred in EntityFramework SqlServer dll but was not handled in user   code  Additional information  The underlying provider failed on Open    SOLUTION    Add in Model      DatabaseGenerated DatabaseGeneratedOption Identity     Key    Namespace     using System ComponentModel DataAnnotations  using System ComponentModel DataAnnotations Schema   Example   namespace MvcApplication1 Models      Table  tblEmployee      public class Employee          DatabaseGenerated DatabaseGeneratedOption Identity        Key      public int EmplyeeID   get  set                 public string Name   get  set        public string Gender   get  set        public string City   get  set

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Possible solution is described in this Code Project tip   As folks mentioned IIS user network service user credentials while trying to log in sql server  So just change the Application pool settings in your IIS   Open Internet Information Service Manager Click on Application Pools in left navigation tree  Select your version Pool  In my case  I am using ASP  Net v4 0  If you dont have this version  select DefaultAppPool  Right click on step 3  and select advanced settings  Select Identity in properties window and click the button to change the value  Select Local System in Built-in accounts combo box and click ok  That s it  Now run your application  Everything works well

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Seems like a connection issue  You can use the Data link properties to find if the connection is fine  Do the following    Create a blank notepad and rename it to  X UDL  Double click to open it Under connections tab choose the server name enter the name use the correct credentials and DB Click OK to save it     Now open the file in Notepad and compare the connection string properties

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If you are using a local  mdf file   probably a sync software such Dropbox attempted to sync two log files   ldf  in two different computers you can delete the log files from the bin Directory and make sure the  mdf properties- Copy to Output Directory - Copy if newer that will copy the selected DB file and it s log to the bin Directory   Alert- if your DB file has only changed in the bin Directory all the changes ill be discarded

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I got this problem while continuing execution of a unit test that calls a method that is using parallel processing I know there are parts of EF that are not thread-safe  so I am wondering if it is a conflict where the connection is being open and closed out of sync with the operations    My stack trace showed this        at System Threading Tasks Task ThrowIfExceptional Boolean includeTaskCanceledExceptions     at System Threading Tasks Task Wait Int32 millisecondsTimeout  CancellationToken cancellationToken     at System Threading Tasks Task Wait      at System Threading Tasks Parallel ForWorker TLocal  Int32 fromInclusive  Int32 toExclusive  ParallelOptions parallelOptions  Action 1 body  Action 2 bodyWithState  Func 4 bodyWithLocal  Func 1 localInit  Action 1 localFinally     at System Threading Tasks Parallel ForEachWorker TSource TLocal  IList 1 list  ParallelOptions parallelOptions  Action 1 body  Action 2 bodyWithState  Action 3 bodyWithStateAndIndex  Func 4 bodyWithStateAndLocal  Func 5 bodyWithEverything  Func 1 localInit  Action 1 localFinally     at System Threading Tasks Parallel ForEachWorker TSource TLocal  IEnumerable 1 source  ParallelOptions parallelOptions  Action 1 body  Action 2 bodyWithState  Action 3 bodyWithStateAndIndex  Func 4 bodyWithStateAndLocal  Func 5 bodyWithEverything  Func 1 localInit  Action 1 localFinally     at System Threading Tasks Parallel ForEach TSource  IEnumerable 1 source  Action 1 body    So that s the clue I followed  When I went back to a single-thread foreach instead of Parallel ForEach the issue went away    Joey

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My client reported this error  I found that he was messing with   ldf files  He copied  ldf file on one database and renamed it to match a second database  which I asked him to place in a folder    I replicated the same scenario  and got this same error in my development system  Error got fixed after deleting the  ldf file s

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In my case  I resolved the error by adding connection password in the connection string   While setting up the EF model  I had selected the option to exclude sensitive data from connection string  So  the password was not included initially

[c#] Entity Framework The underlying provider failed on Open

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