Develop Reference

I can't connect to a local SQL Server instance via Entity Framework using Windows authentication

I can't connect to my local SQL Server Express instance via Entity Framework. When I try to run the update-database command, I get this error message.
Login failed for user ''. Reason: An attempt to login using SQL authentication failed.
Server is configured for Integrated authentication only.
Error: 18456, Severity: 14, State: 58.
From what I understand, Visual Studio is attempting to log in to SQL Server via a user account even though I've requested that Windows authentication is used in the connection string.
I can still access the server via SSMS.
What I've tried. None of which helped
Different variations of the connection string
Opened port 1433
Created a test UDL file to test the connection.
A clean reinstall of SQL Server Express (not sure I managed to clean up all the files)
Checked the SQL Server browser is running
Checked server instance is running
Enabled TCP/IP & named pipes
Tried connecting via tcp which works
Added Integrated Security=SSPI to connection string
Changed server to accept Windows authentication and SQL Server authentication.
Restarting PC
This is a new laptop on windows 11, I don't know if that is causing any issues as I've never had an issue with this process on Windows 10.
I seem to have two instances; .\SQLEXPRESS & (localdb)\\MSSQLLocalDB I'm not sure if this is causing some conflict or if this is the intended behaviour.
Here is the connection string, I pulled this from the server explorer within Visual Studio so I am pretty sure this is correct. On top of that, I have tried numerous variations of this to attempt to fix the issue
"DefaultConnection": "Data Source=LAPTOP-51LB4QTQ\\SQLEXPRESS;Initial Catalog=MicroBlog;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"
This is where I get the connection string in my Program.cs file
builder.Services.AddDbContext<BlogContext>(opt => opt.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));
var app = builder.Build();
At this point I'm completely lost, I've read a lot of articles but have not come across any fixes. I'm not a dba just a programmer so have limited knowledge of this side of SQL Server.

You may try like below:
In Web.config file:
<connectionStrings>
<add name="DefaultConnection" connectionString="Data Source=SUBRATATALUKDER;Initial Catalog=MyDB;Integrated Security=True;" providerName="System.Data.SqlClient"/>
</connectionStrings>
In appsettings.json file:
"ConnectionStrings": {
"DefaultConnection": "Server=SUBRATATALUKDER;Database=MyDB;Trusted_Connection=True;TrustServerCertificate=True;",
}
Note:
Server Name = SUBRATATALUKDER
Database Name = MyDB
100% tested.

C# app with SqlClient does not work on another computer

I have written an application that uses SqlClient and a local mdf database. However, it does not work on another machine (throwing an exception that the server cannot be run) and I assume this is because there is no SQL server installed? But I thought that using local database and SqlClient elimites the need for the server, something like the old SQL CE. Is that the problem?
EDIT Exception: System.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while extablishing 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
As for connection string, I keep the one generated by Visual Studio Express, just modify the path to use the app folder.
SqlConnection s = new SqlConnection(#"Data Source = (LocalDB)\MSSQLLocalDB; AttachDbFilename ="+ System.IO.Path.GetDirectoryName(Application.ExecutablePath)+ #"\Database1.mdf; Integrated Security = True");
Is there a simple way how to rework this so that my app does not require SQL server installed? All I need is to have it use the local database file in its folder.

Connection String to SQL Server 2014 Failing

A developer friend and I could not get a connection string to work on my PC.
I'm calling to a local db instance which is Management Studio 2014 (one of the free editions).
It fails on connection.Open();
The Code is:
string conn = ConfigurationManager.ConnectionStrings["DatabaseConnection"].ToString();
IDbConnection connection = new SqlConnection(conn);
connection.Open();
App.Config is:
<connectionStrings>
<add name="DatabaseConnection"
connectionString="data source=MIKE-PC; initial catalog=dbname;integrated security =True"
providerName="System.Data.SqlClient" />
</connectionStrings>
The Error is:
An unhandled exception of type 'System.Data.SqlClient.SqlException'
occurred in System.Data.dll
Additional information:
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)

There are many possible issues that you can check to correct this:
Make sure your database server is running: open run or shortcut Window + R, type services.msc, hit enter. Make sure the SQL Server (SQLEXPRESS) service is running.
Open your SQL Management Studio. Try to connect to your database from there to make sure your server name (data source) and database name (initial catalog) are correct.
Make sure your database can be accessed using Integrated Security. You can tell that it does if you can connect to your database using "Windows Authentication" from your MS SQL Server Management Studio.
Hope this help.

SQL Server connection string causing error?

In a Winforms application, I have a connection string that causes an error
data source=(local);initial catalog=RegisterDB;persist security info=False
Error:
An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll
Additional information:
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)
Thanks for the help Arif Ansari but it still gives the same error.
I'm using Microsoft Visual Studio 2013 Express with SQL Server. I created the database from within Microsoft Visual Studio 2013 Express
Can anyone help?
Hi marc_s
Sorry it didnt work. I created the Database RegisterDB manually with Microsoft Visual Studio 2013 Express in server "(localdb)\v11.0"
Can anyone help ???????

Please Try it
SqlConnection con = new SqlConnection("Data Source=(local);Database=RegisterDB;Integrated Security= true");

try this query as your connection string format
Server=myServerName\myInstanceName;Database=myDataBase;User Id=myUsername;
Password=myPassword;
or this
Server=myServerAddress;Database=myDataBase;Trusted_Connection=True;
basically check the instance of the server that you are running.
Check if the instance service is running or not.
Type services.msc in the start menu to open the Services List.
Check for the name SQL SERVER (your instance name).
If the instance status is Started, issue is in your connection string or user permissions.
Else if the status is empty or stopped, start the instance and then try connecting.
you may also refer this site for connection string format.

The SQL Server that comes with Visual Studio 2013 is the 2012 Express version - and that by default install the "LocalDB" support.
So I would try this connection string instead:
"data source=(localdb)\v11.0;initial catalog=RegisterDB;Integrated Security=SSPI;"
Does that work? If not: are you auto-creating the database, or if not, did you manually create that database RegisterDB that you're referencing in the connection string?

error while Connecting .mdf database

I developed a small project in visual studio 2010. In my project I attach a service-based database named database1.mdf.
My connectionString is :
Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True
It works fine on my developer pc but it throws an exception on a client's pc.
Exception is :
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: 26 - Error Locating Server/Instance
Specified)
I don't understand what is happening.

Two things need to occur before you can connect to a SQL Server Express database.
SQL Server Express must be installed on the target server. Having the file present isn't sufficient. (This is what the error you're experiencing likely means).
The path to your database file should be an absolute path to rule out the possibility of a file location error.

this connection string is for your developer machine. you share your database on the network. you also must update your connection string by adding ip address of your server.