MSSQL Error 'The underlying provider failed on Open'

I was using an .mdf for connecting to a database and entityClient. Now I want to change the connection string so that there will be no .mdf file.

Is the following connectionString correct?

<connectionStrings>
   <!--<add name="conString" connectionString="metadata=res://*/conString.csdl|res://*/conString.ssdl|res://*/conString.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=.\SQL2008;AttachDbFilename=|DataDirectory|\NData.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient" />-->
   <add name="conString" connectionString="metadata=res://*/conString.csdl|res://*/conString.ssdl|res://*/conString.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=.\SQL2008;Initial Catalog=NData;Integrated Security=True;Connect Timeout=30;User Instance=True;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient" />

Because I always get the error:

> The underlying provider failed on Open

I had this error and found a few solutions:

Looking at your connection string, it looks valid. I found this blog post, the problem here is that they were using Integrated Security. If you are running on IIS, your IIS user needs access to the database.

If you are using Entity Framework with Transactions, Entity Framework automatically opens and closes a connection with each database call. So when using transactions, you are attempting to spread a transaction out over multiple connections. This elevates to MSDTC.

(See this reference for more information.)

Changing my code to the following fixed it:

using (DatabaseEntities context = new DatabaseEntities())
{
    context.Connection.Open();
    // the rest
}

context.Connection.Open() didn't help solving my problem so I tried enabling "Allow Remote Clients" in DTC config, no more error.

In windows 7 you can open the DTC config by running dcomcnfg, Component Services -> Computers -> My Computer -> Distributed Transaction Coordinator -> Right click to Local DTC -> Security.

You should see innerException to see what the inner cause of throwing of error is.

In my case, the original error was: >Unable to open the physical file "D:\Projects2\xCU\xCU\App_Data\xCUData_log.ldf". Operating system error 5: "5(Access is denied.)". An attempt to attach an auto-named database for file D:\Projects2\xCU\xCU\App_Data\xCUData.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.

which solved by giving full permission to current user for accessing related mdf and ldf files using files' properties.

I found the problem was that I had the server path within the connection string in one of these variants:

SERVER\SQLEXPRESS
SERVER

When really I should have:

.\SQLEXPRESS

For some reason I got the error whenever it had difficulty locating the instance of SQL.

This is common issue only. Even I have faced this issue. On the development machine, configured with Windows authentication, it is worked perfectly:

<add name="ShoppingCartAdminEntities" connectionString="metadata=res://*/ShoppingCartAPIModel.csdl|res://*/ShoppingCartAPIModel.ssdl|res://*/ShoppingCartAPIModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=.\SQlExpress;initial catalog=ShoppingCartAdmin;Integrated Security=True;multipleactiveresultsets=True;application name=EntityFramework&quot;" providerName="System.Data.EntityClient" />

Once hosted in IIS with the same configuration, I got this error:

> The underlying provider failed on Open

It was solved changing connectionString in the configuration file:

<add name="MyEntities" connectionString="metadata=res://*/ShoppingCartAPIModel.csdl|res://*/ShoppingCartAPIModel.ssdl|res://*/ShoppingCartAPIModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=MACHINE_Name\SQlExpress;initial catalog=ShoppingCartAdmin;persist security info=True;user id=sa;password=notmyrealpassword;multipleactiveresultsets=True;application name=EntityFramework&quot;" providerName="System.Data.EntityClient" />

Other common mistakes could be:

1. Database service could be stopped
2. Data Source attributes pointing to a local database with Windows authentication and hosted in IIS
3. Username and password could be wrong.

When you receive this exception, make sure to expand the detail and look at the inner exception details as it will provide details on why the login failed. In my case the connection string contained a user that did not have access to my database.

Regardless of whether you use Integrated Security (the context of the logged in Windows User) or an individual SQL account, make sure that the user has proper access under 'Security' for the database you are trying to access to prevent this issue.

I had a similar issue with the SQL Server Express Edition on Windows Server 2003. I simply added the network service as a user in the database security.

The SQL Server Express service were not set tostart automatically.

1. Go to control panel
2. Administrative Tools
3. Service
4. Set SQL Server express to start automatically by clicking on it
5. Right click and start the service

I hope that will help.

This can also happen if you restore a database and the user already exists with different schema, leaving you unable to assign the correct permissions.

To correct this run:

USE your_database
EXEC sp_change_users_login 'Auto_Fix', 'user', NULL, 'cf'
GO
EXEC sp_change_users_login 'update_one', 'user', 'user'
GO

I posted a similar issue here, working with a SQL 2012 db hosted on Amazon RDS. The problem was in the connection string - I had "Application Name" and "App" properties in there. Once I removed those, it worked.

https://stackoverflow.com/questions/16096786/entity-framework-5-and-amazon-rds-the-underlying-provider-failed-on-open?noredirect=1#comment23033375_16096786

Make sure that each element value in the connection string being supplied is correct. In my case, I was getting the same error because the name of the catalog (database name) specified in the connection string was incorrect.

I had a similar issue with exceptions due to the connection state, then I realized I had my domain service class variable marked as static (by mistake).

My guess is that once the service library is loaded into memory, each new call ends up using the same static variable value (domain service instance), causing conflicts via the connection state.

I think also that each client call resulted in a new thread, so multiple threads accessing the same domain service instance equated to a train wreck.

I got rid of this by resetting IIS, but still using Integrated Authentication in the connection string.

I had the same problem but what worked for me was removing this from the Connection String:

persist security info=True

Defining a new Windows Firewall rule for SQL Server (and for port 1433) on the server machine solves this error (if your servername, user login name or password is not wrong in your connection string...).

I had a similar error with the inner exception as below:

> operation is not valid for the state of the transaction

I could resolve it by enabling DTC security settings.

Go To Properties of DTC, under Security Tab, check the below

• Network DTC Access
• Allow RemoteClients
• Transaction Manager Communication
• Allow Inbound
• Allow Outbound

If you happen to get this error on an ASP.NET web application, in addition to other things mentioned check the following:

1. Database User Security Permissions (which users are allowed access to your database.
2. Check your application pool in IIS and make sure it's the correct one that is allowed access to your database.

I was searching all over the web for this problem. I had the wrong name in the connection string, please check you connection string in web.config. I had name="AppTest" but it should have been name="App".

In my AppTestContext.cs file I had:

public AppTestContext() : this("App") { }

Wrong connection string:

<add connectionString="Data Source=127.0.0.1;Initial Catalog=AppTest;Integrated Security=SSPI;MultipleActiveResultSets=True" name="AppTest" providerName="System.Data.SqlClient" />

Right connection string:

<add connectionString="Data Source=127.0.0.1;Initial Catalog=AppTest;Integrated Security=SSPI;MultipleActiveResultSets=True" name="App" providerName="System.Data.SqlClient" />

A common mistake that I did because I was moving application from once pc to another and none of the above worked was that I forgot to copy the connection string to both App.Config and Web.Config!

I was also facing the same issue. Now I have done it by removing the user name and password from the connection string.

For me it was just a simple mistake:

I used Amazon EC2, and I used my elastic IP address in the connection string, but when I changed IP addresses I forgot to update my connection string.

I had this error suddenly happen out of the blue on one of our sites. In my case, it turned out that the SQL user's password had expired! Unticking the password expiration box in SQL Server Management Studio did the trick!

I had a similar problem: In my test-cases executions I always got this error. I found out, that my "Distributed Transaction Service" was not started (run: services.msc -> start "Distributed Transaction Service" (best to set it to start automatic)). After I did that, it worked like a charm...

I had the same issue few days ago, using "Integrated Security=True;" in the connection string you need to run the application pool identity under "localsystem" Sure this is not recommended but for testing it does the job.

This is how you can change the identity in IIS 7: http://www.iis.net/learn/manage/configuring-security/application-pool-identities

In IIS set the App Pool Identity As Service Account user or Administrator Account or ant account which has permission to do the operation on that DataBase.

In my case I had a mismatch between the connection string name I was registering in the context's constructor vs the name in my web.config. Simple mistake caused by copy and paste :D

    public DataContext()
        : base(nameOrConnectionString: "ConnStringName")
    {
        Database.SetInitializer<DataContext>(null);
    }

I had this problem because the Application Pool login this app was running under had changed.

In IIS:

• Find the Application pool by clicking on your site and going to Basic Settings.

• Go to Application Pools.

• Click on your site's application pool.

• Click on Advanced Settings.

• In Identity, enter account login and password.

• Restart your site and try again.

NONE of the answers worked for me

I think that some of us all make silly mistakes, there are 100 ways to fail ...

My issue was new project, I setup all the configuration in another project, but the caller was a Web Api project in which I had to copy the same connection string in the Web api project.

I think this is crazy considering I was not even newing up dbcontext or anything from the web api.

Otherwise the class library was trying to look for a Database named

TokenApi.Core.CalContext   

of which my project is named TokenApi.Core and the CalContext is the name of the connection string and the file name

I have solved this way.

> Step 1: Open Internet Information Service Manager

Step 2: Click on Application Pools in left navigation tree.

Step 3: Select your version Pool. In my case, I am using ASP .Net v4.0. If you dont have this version, select DefaultAppPool.

Step 4: Right click on step 3, and select advanced settings.

Step 5: Select Identity in properties window and click the button to change the value.

Step 6: Select Local System in Built-in accounts combo box and click ok. That's it. Now run your application. Everything works well.

Codeproject Solution : the-underlying-provider-failed-on-open

You could try to replace the metadata:

metadata=res:///conString.csdl|res:///conString.ssdl|res://*/conString.msl

to:

metadata=res://*/;