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C# | Can't insert Data into LocalDB but it doesn't show any error [duplicate]

Apparently, using AttachDbFilename and user instance in your connection string is a bad way to connect to a DB. I'm using SQL server express on my local machine and it all seems to work fine. But what's the proper way to connect to SQL server then?
Thanks for your explanation.

Using User Instance means that SQL Server is creating a special copy of that database file for use by your program. If you have two different programs using that same connection string, they get two entirely different copies of the database. This leads to a lot of confusion, as people will test updating data with their program, then connect to a different copy of their database in Management Studio, and complain that their update isn't working. This sends them through a flawed series of wild goose chase steps trying to troubleshoot the wrong problem.
This article goes into more depth about how to use this feature, but heed the very first note: the User Instance feature has been deprecated. In SQL Server 2012, the preferred alternatives are (in this order, IMHO):
Create or attach your database to a real instance of SQL Server. Your connection string will then just need to specify the instance name, the database name, and credentials. There will be no mixup as Management Studio, Visual Studio and your program(s) will all be connecting to a single copy of the database.
Use a container for local development. Here's a great starter video by Anna Hoffman and Anthony Nocentino, and I have some other resources here, here, and here. If you're on an M1 Mac, you won't be able to use a full-blown SQL Server instance, but you can use Azure SQL Edge if you can get by with most SQL Server functionality (the omissions are enumerated here).
Use SqlLocalDb for local development. I believe I pointed you to this article yesterday: "Getting Started with SQL Server 2012 Express LocalDB."
Use SQL Server Compact. I like this option the least because the functionality and syntax is not the same - so it's not necessarily going to provide you with all the functionality you're ultimately going to want to deploy. Compact Edition is also deprecated, so there's that.
Of course if you are using a version < SQL Server 2012, SqlLocalDb is not an option - so you should be creating a real database and using that consistently. I only mention the Compact option for completeness - I think that can be almost as bad an idea as using AttachDbFileName.
EDIT: I've blogged about this here:
Bad Habits : Using AttachDBFileName

In case someone had the problem.
When attaching the database with a connection string containing AttachDBFile
with SQLEXPRESS, I noticed this connection was exclusive to the ASP.NET application that was using the database. The connection did block the access to all other processes on the file level when made with System.Data.SqlClient as provider.
In order to assure the connection to be shareable with other processes
instead use DataBase to specify the database name in your connection string
Example or connection string :
Data Source=.\SQLEXPRESS;DataBase=PlaCliGen;User ID=XXX;password=ZZZ; Connect Timeout=30
,where PlaCliGen is the name (or logical name) by which SQLEXPRESS server knows the database.
By connecting to the data base with AttachDBFile giving the path to the .mdf file
(namely : replacing DataBase = PlacliGen by AttachDBFile = c:\vs\placligen\app_data\placligen.mdf) the File was connected exclusively and no other process could connect to the database.

Database reader generates exception An attempt to attach an auto-named database for file .. failed [duplicate]

Apparently, using AttachDbFilename and user instance in your connection string is a bad way to connect to a DB. I'm using SQL server express on my local machine and it all seems to work fine. But what's the proper way to connect to SQL server then?
Thanks for your explanation.

Using User Instance means that SQL Server is creating a special copy of that database file for use by your program. If you have two different programs using that same connection string, they get two entirely different copies of the database. This leads to a lot of confusion, as people will test updating data with their program, then connect to a different copy of their database in Management Studio, and complain that their update isn't working. This sends them through a flawed series of wild goose chase steps trying to troubleshoot the wrong problem.
This article goes into more depth about how to use this feature, but heed the very first note: the User Instance feature has been deprecated. In SQL Server 2012, the preferred alternatives are (in this order, IMHO):
Create or attach your database to a real instance of SQL Server. Your connection string will then just need to specify the instance name, the database name, and credentials. There will be no mixup as Management Studio, Visual Studio and your program(s) will all be connecting to a single copy of the database.
Use a container for local development. Here's a great starter video by Anna Hoffman and Anthony Nocentino, and I have some other resources here, here, and here. If you're on an M1 Mac, you won't be able to use a full-blown SQL Server instance, but you can use Azure SQL Edge if you can get by with most SQL Server functionality (the omissions are enumerated here).
Use SqlLocalDb for local development. I believe I pointed you to this article yesterday: "Getting Started with SQL Server 2012 Express LocalDB."
Use SQL Server Compact. I like this option the least because the functionality and syntax is not the same - so it's not necessarily going to provide you with all the functionality you're ultimately going to want to deploy. Compact Edition is also deprecated, so there's that.
Of course if you are using a version < SQL Server 2012, SqlLocalDb is not an option - so you should be creating a real database and using that consistently. I only mention the Compact option for completeness - I think that can be almost as bad an idea as using AttachDbFileName.
EDIT: I've blogged about this here:
Bad Habits : Using AttachDBFileName

In case someone had the problem.
When attaching the database with a connection string containing AttachDBFile
with SQLEXPRESS, I noticed this connection was exclusive to the ASP.NET application that was using the database. The connection did block the access to all other processes on the file level when made with System.Data.SqlClient as provider.
In order to assure the connection to be shareable with other processes
instead use DataBase to specify the database name in your connection string
Example or connection string :
Data Source=.\SQLEXPRESS;DataBase=PlaCliGen;User ID=XXX;password=ZZZ; Connect Timeout=30
,where PlaCliGen is the name (or logical name) by which SQLEXPRESS server knows the database.
By connecting to the data base with AttachDBFile giving the path to the .mdf file
(namely : replacing DataBase = PlacliGen by AttachDBFile = c:\vs\placligen\app_data\placligen.mdf) the File was connected exclusively and no other process could connect to the database.

SQL Server connection errors when moving .net app to new server

I have a number of .NET web apps on a Server 2008 machine that I'm trying to migrate to a Server 2019 machine, and some of them are giving me problems connecting to SQL Server 2016 instance on another server after moving them.
The error I get is
System.Data.SqlClient.SqlException (0x80131904): 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: SQL Network Interfaces, error: 25 - Connection string is not valid) ---> System.ComponentModel.Win32Exception (87): The parameter is incorrect
This one is a .NET Core 2.2 web app. (.net core 2.2 server package installed on server) the connection string is like
"Server=mysqlserver\myinstance,3050;Database=Idea;Trusted_Connection=True;"
and is using Entity Framework/DbContext to connect.
The app in IIS has an app pool created for this app, set up the same as it was running on the old server: No Managed Code, Identity set as a domain user "domain\user".
Ping from new app server to database server works. Running SSMS as the domain user on the new server connects to the database fine and can view data through management studio.
So I don't know if there is something different in Server 2019 about the way it's trying to connect to SQL Server or what? I've been banging my head on this for a few days now. .NET 4.0 apps are also having the same errors trying to connect to other databases on this same instance.
The weird thing, is some other apps work fine, connecting to a different SQL 2016 instance on a different server, but they are also different .net versions, like older .NET 4.0 web apps, but they are running as app pools with different domain accounts for each app fine.
It seems all .NET Core or .net 4.0 web apps on this server are having trouble connecting to this one database instance from this server, but back on the old web app server they work fine.
Any ideas of anything else I can check?
Edit: I found the error is actually when connecting to a new SQL Server, even from the old app server it still gets the same error. I have 2 connections in this application, so I thought it was the first one, but it was actually the 2nd one. So it's something more to do with the new SQL server instance. Again, connections from SSMS work fine with this user, but not from the web app.
Edit2: After more testing, it's definitely something to do if there is Server 2019 in the mix. From 2019 app server to 2019 db server fails. From 2008 app server to 2019 db server fails. From 2019 app server to 2016 db server fails. From 2008 app server to 2016 db server succeeds.
Edit 3: I feel like I'm going crazy here. One of the apps, I tried to change ASPNETCORE_ENVIRONMENT to Development so that I could see more detailed errors on screen, so I set the appsettings.Development.json to the exact same as the appsettings.Production.json and then the connection works! Switching it back to production it gets the error again. The entire file is the exact same text. How does that even make any sense? I even tried explicitly setting the environment variable to Production instead of letting it just pick it up as the default.
Edit 4: I've solved half of the problems I've been having now.
For whatever reason, the connection string that I copied from one of the spreadsheets in the beginning had crazy hidden characters in it so that’s why it was saying the sql server didn’t exist.
I can’t see them at all in any editor and only found it by VS Code compare saying the line was different but not seeing any difference I broke it into chunks and found the spot. We found when we opened it in WordPad, that was the only place that would show it, see below.

I'm fairly sure the solution is to remove the instance name from the connection string...
"Server=mysqlserver,3050;Database=Idea;Trusted_Connection=True;"
Refer to these questions question1 & question2
"It's not necessary to specify an instance name when specifying the port."

Problem was due to hidden characters in the connection string. See my Edit 4. Other problems leftover were unrelated.

Try to create an user in the database using the same AppPool name that you used to configure your application in IIS.
Here's a "how to" create the user in the database:
https://engram404.net/grant-sql-permissions-to-iis-apppool-user/
It worked for me.
Otherwise here's an "why" it happends:
You're telling in your connectionString that it will be using an trusted connection "Trusted_Connection=True;"
If you do not want to create the user as described earlier, you should remove the Trusted_Connection=True; and use your connection string like this:
Server=mysqlserver\myinstance,3050;Database=Idea;User Id=SetYourUser;Password=SetYourPassword"

I know you happened to solve this, but still..
You can't connect to a MySQL database with System.Data.SqlClient - It is configured for an SQL database, not MySQL
You can find the MySQL Data Connector Here. (You can otherwise download it from Nuget)
If you downloaded it from Nuget, then skip this step.
After downloading the package, you can add it as a reference in your project, by right-clicking the References item in the Solution Explorer, then click Add Reference... - The Reference Manager window will then open. Click the Browse item in the left-menu, then click the Browse button, and navigate to the directory of which the package was saved.
Now, after successfully downloading and installing the package, add this line to your code:
using MySql.Data.MySqlClient;
The correct syntax for connecting to your MySQL Database, using MySql.Data.MySqlClient;, would be:
string connectionInfo = #"Server=localhost;Database=your_database;User ID=root;Password=123456";
So, overall, your code would look like:
using(MySqlConnection con = new MySqlConnection(connectionInfo))
{
con.Open();
MessageBox.Show("Successful Connection!");
}
(Code / part of answer is derived from here.)
I hope I could help anyone else with this problem :)

Unable to connect to SQL with VS 2012

I'm unable to connect to my database that is located on my laptop. Now I'm trying to access it locally from within the same laptop.
i'm using this connection string:
Server=localhost,49172;database=databasename;uid=user;pwd=password;
The fields are filled with respective information. I also tried putting my latop's name instead of localhost. I tried different port numbers with no use .
I got an error:
cn.ServerVersion threw and exception - InvalidOpertionException.(network related eroror) The next timem the error sayingthe connectionwas successful but there was a time during the pre-login handshake.
I'm using Visual Studio 2012 with SQL Server 2012. I also tried installingthe mysql connector net. My database was created with phpmyadmin web interface that uses the xampp control panel.
Any help please? I'm making an aspx webpage with c# as the code behind.
I tried adding these tags Integrated security and removing the user and password tags with no luck

How you connect the MySQL server (You mention SQL but later Mysql so hence I write this answer for Mysql).
Try to open services. Check if Mysql is running or not. Check if firewall make it hard to connect to the mysql services.
Try to remove database from connectionstring (that you pasted to connect). If that works it means you didn't have access to Database.
BTW this connectionstring is totally incorrect. "Server=localhost,49172;database=databasename;uid=user;pwd=password;"
Are you sure 49172 is the port you are using. Try to define port like this way https://www.connectionstrings.com/mysql/ to fix it.
If you didn't changed your port then by default it will be 3306.
I hope this will fix your issues.

Can't connect to SQL Server database

I'm currently developing a web application using asp.net c#. I got a server where I today was
going to publish my website and its database. Its a server that runs Windows Server 2008 R2.
But I have one issue:
My website doesn't seem to get access to the database. If I run the website from another computer on my local network I can access the server's database, BUT I can't when I run the website from the same server where the database is. This is really weird. I hope someone can help.
I just get an error that says, it can't access the database.
The most weird of all is that I'm using the same connection string on both computers, but it still doesn't work. Are there maybe some sort of settings in Windows Server 2008?
Here is my connection string:
<add name="ConnectionString"
connectionString="Data Source=AXELS;Initial Catalog=Sailor;Persist Security Info=True;User ID=sa;Password=saab123"
providerName="System.Data.SqlClient" />

Since the connection works on one machine and not on another, I'd guess you have an issue with a firewall or similar - but it will be hard to tell until we see the actual error message. Until then, there are a few things you might want to do:
If it appears as if the connection has to time out before you get the error, it indicates a connectivity problem. Do you have a firewall between the two servers? Does the database server have a firewall that explicitly lets your machine (or internal) machines get through, but hasn't been setup to let the webserver get through? You have to make sure that port 1433 is open on the server.
Are there other sites on the webserver that can connect to the database?
If you have console access to the server, try to set up an ODBC from the server to the database - usually in Control Panel -> Data Sources (ODBC). If you set up a connection with the same DB Server, username and password and test the connection, you might get some pointers to what is wrong.
If the above doesn't provide you with an answer, I'd try to go through the steps described here:
http://blog.sqlauthority.com/2009/05/21/sql-server-fix-error-provider-named-pipes-provider-error-40-could-not-open-a-connection-to-sql-server-microsoft-sql-server-error/
And if that fails, take a look at this - which is apparently only valid when you get SQL Network Interfaces, error: 26
http://blogs.msdn.com/b/sql_protocols/archive/2007/05/13/sql-network-interfaces-error-26-error-locating-server-instance-specified.aspx

This is probably a permission problem.
You need to show us your connection string so we can see how exactly you try to connect to your database.
For example, if you are using Windows authentication, maybe your app runs under different accounts on both machines - and the account on the other computers has permission to access the database, but the account on the database server has not.

Have you checked the if the protocols you are using are enabled on the SQL Server e.g.
C:\Windows\System32\cliconfg.exe -- 64 bit version
C:\Windows\SysWOW64\cliconfg.exe -- 32 bit version
or check SQL Server Configuration Manager 'SQL Server Native Client *' tabs.

This is only applicable if you do not use Windows Authentication, else read the post about priviliges from Christian Specht - in this case I agree.
The fact that you can connect from another PC on the network means that all you database settings, user accounts and permissions are probably set up correct.
It seems there might be a issue with the way the server resolves localhost, as it will try to resolve the Data Source to localhost because AXELS = localhost on that machine.
Have a look at your hosts file and see if there's any funny pointers except for the default.
Located in C:\Windows\System32\drivers\etc
There should be an entry: 127.0.0.1 localhost