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What Is the Syntax for Including the Service Name in a Connection String?

I have a C# ASP.Net MVC web application. I am trying to successfully connect to an Oracle database.
I am getting a "ORA-12514: TNS:listener does not currently know of service requested in connect descriptor" error.
I do not have access to the server the database is on. But I do have access to Oracle SQL Developer, which I have installed on my machine.
In my C# code I am setting the connection string like this:
ConnectionString = "DataSource=XXX.XX.XXX.XXX/abcd,1521;User ID=userid;Password=password;";
abcd should be the service name. and 1521 is the port number.
I understand that my connection string might not be the cause of the error, but I want to rule it out. Also, I know the more proper way of doing things is probably to set the connection string in web.config and retrieve it as needed, but I am doing it this way just for ease of testing until I know I am able to connect to the database successfully.
What is weird to me, is that I was able to connect to the database using Oracle SQL Developer using the same IP address, port number, service name, username, and password I am using in my connection string.
Primarily, I would like help knowing if my connection string looks valid. If you have additional thoughts about what the issue could be, that would also be appreciated.
using this command in Oracle SQL Developer:
select sys_context('userenv','service_name') from dual;
I am able to determine that the service name I am using in my connection string is one that exists, although I guess this does not guarantee that the service is up.
I am not a DBA by any means. In fact, I am still new to .Net and web development in general, but I have been assigned to troubleshoot this issue. Any help is appreciated.

I don't recall seeing the following format
DataSource=XXX.XX.XXX.XXX/abcd,1521
as valid (which doesn't mean its not, I've just not seen it).
The more common ones I've seen are:
DataSource=XXX
where XXX is a reference to your tnsnames.ora file
DataSource=//nnn.nnn.nnn.nnn/service_name
DataSource=//nnn.nnn.nnn.nnn:port/service_name
So maybe try those variants and see how you go. There's also more definitive list of alternatives at https://www.c-sharpcorner.com/UploadFile/nipuntomar/connection-strings-for-oracle/

I ended up figuring this out. My connection string format I don't t think was correct. I changed it to be:
ConnectionString = "DataSource=XXX.XX.XXX.XXX/abcd;User ID=userid;Password=password;";
Basically, I just took off the port number. In my case, the default port was what I needed anyway. Not sure what I would have done had I needed to specify the port number.

As new to Oracle I struggled a few days finding solution to this
this article helped me alot
As of Oracle 21 c
This is my Connection string for C#
Password=dev;Persist Security Info=True;User ID=Dev;Data Source=localhost:1521/XEPDB1
Keep in mind Dev is Username which is also the Schema name for Oracle

Fail to open the database

Well, i know this question was asked many times on this platform. Nothing seems to work for me. I looked at this Cannot open database "test" requested by the login. The login failed. Login failed for user 'xyz\ASPNET'. I fully understand that.
The case is the database was created by default when i created the application. I choose the Individual Authentication. I then expand the database using the Entity Framework 6. I want to create a CRUD operation through the Entity Framework 6 by generating .edmx file. The error occurs when I tried to attach the database to the program.
I tried opening it with MSSQL Server to assign right to the user. After it will complain the file is corrupt. If anyone will help me to open it or how to generate a CRUD on that. I will be thankful.

You can see your connection string something like below
Data Source=.\SQLExpress;Initial Catalog=something;Integrated Security=True
Remove Integrated Security=True from your connection string then it will work
Update
it is recommended to keep Integrated Security . When false, User ID and Password are specified in the connection. When true, the current Windows account credentials are used for authentication.Possible states are true, false, yes, no, and sspi Read More

C# Program is using my Windows AD authentication to connect to my database instead of the connection string I coded into it. Why?

The title almost says it all, but I'll provide a little background.
I am working on adding password hashing to a program written by a team member who rather suddenly departed this world. I have all of the original source, and have made appropriate changes.
The issue arises when, after looking at the active connections on the database, the connection it is making is under my Windows Activate Directory username, rather than the connection string I give to SqlConnection().
I am not traditionally a C# programmer, but the language is very easy to pick up on. For those more accustomed to C#'s particular ins and outs, what can I do to assure that I'm connecting through the connection string passed to SqlConnection()?
This is important since people who are not me and have no authorization to the database are not going to be able to even validate their DB stored usernames + password without using that connection string.
EDIT: My current connection string is as follows:
user id=[uid];password=[password];server=[server];Trusted_Connection=yes;database=[dbName];connection timeout=30"

Trusted_Connection is an alias for Integrated Security, which means "use my Windows account". Remove it from your connection string.

Connection String management for a desktop application

I created a desktop application in C#/WPF which connects to a SQL Server 2008 instance through a constant connection string specified in code as follows (for testing purposes):
private string GetConnectionString()
{
//test
return "Data Source=[server IP]; Initial Catalog=[database name]; User ID=[user ID]; Password=[smart password];";
}
The application will be used by various users and will be deployed via ClickOnce, a .zip archive or a custom installer. It also has a separated custom login functionality by requesting an application-access username and password.
Which is the best practice to store the connection string details for my desktop application (IP, database, SQL Server user, password)? If the connection string changes over night, which is the best method to update it without forcing users to update to the latest version of my application? Users should not be able to see/intercept/decompile the connection string, so I guess I must use some sort of encryption.
Do you have any kind of suggestion for my inquiry?

Even if you compile your connection strings into the application, they still can be viewed using the Ildasm.exe (MSIL Disassembler) tool because strings are a part of assembly's metadata.
Maybe this question can help you.

In a desktop application, you can't prevent a determined user from seeing the connection string. Even if you use encryption, a determined user will be able to find and use the encryption key.

If the client is connecting to the database then the connection can be hacked.
This is a sample of connection data in App.Config
<appSettings>
<add key="dbServer" value="svr"/>
<add key="dbDataBase" value="db1"/>
<add key="dbUser" value="sharedUser"/>
<add key="dbPassword" value="easyPassword"/>
</appSettings>
Need a reference to system.configuration
string SvrName = ConfigurationManager.AppSettings["dbServer"];
string DBName = ConfigurationManager.AppSettings["dbDataBase"];
string DBUser = ConfigurationManager.AppSettings["dbUser"];
string DBPassword = ConfigurationManager.AppSettings["dbPassword"];
As for security the answer is a 2 tier application where only the secure server side code connects to the database. This code sample from server side code.
The other benefits of server side is repeated queries from the same connection can gain from indexes in memory from prior query.
You could salt and hash the password read from the AppSettings and obsfuscate the application but you would have to use a static salt so it could be hacked. It would just slow down the hacker.

You need to add an "Application Settings" file to your application. Just right click on your solution -> add -> find something similar to "app configuration". In order to do this you will need some kind of external config file to store the connection string. You could even use a simple file. If worried about people finding the file, you can always encrypt the string and decrypt it in your app.

My opinion is that the safest solution is to have a local DNS entry point to the current SQL machine and the authentication to be Windows authentication.
For example : SQLMACHINE host name pointed to 192.168.1.3 in the DNS server.
This way if the name/IP of the SQL machine changes, only the DNS server needs updated (and possibly the local DNS caches to be invalidated).
Having Windows authentication means that no password will be stored on the local machine so you can safely store the connection string in the .config file with no worries.
My 2 (euro)cents.

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="Data Source=.\SQL2008;AttachDbFilename=|DataDirectory|\NData.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True;MultipleActiveResultSets=True"" 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="Data Source=.\SQL2008;Initial Catalog=NData;Integrated Security=True;Connect Timeout=30;User Instance=True;MultipleActiveResultSets=True"" 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="data source=.\SQlExpress;initial catalog=ShoppingCartAdmin;Integrated Security=True;multipleactiveresultsets=True;application name=EntityFramework"" 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="data source=MACHINE_Name\SQlExpress;initial catalog=ShoppingCartAdmin;persist security info=True;user id=sa;password=notmyrealpassword;multipleactiveresultsets=True;application name=EntityFramework"" providerName="System.Data.EntityClient" />
Other common mistakes could be:
Database service could be stopped
Data Source attributes pointing to a local database with Windows authentication and hosted in IIS
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.

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.

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.

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.
Entity Framework 5 and Amazon RDS - "The underlying provider failed on Open."

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 had the same problem but what worked for me was removing this from the Connection String:
persist security info=True

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

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

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...).

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 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 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 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 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.

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

I get this error when call async EF method from sync Main console (await was skipped).
Because async opening a connection was for an already disposed data context.
Solve: call async EF methods correctly