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SqlConnection, I'm using SQL Server, not LocalDB; so how to

So, in the tutorial I was checking, he uses a Database and connect it using this
SqlConnection conn = new SqlConnection(#"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\RANBAH~1\Documents\testlogin.mdf;Integrated Security=True;Connect Timeout=30");
Although, I use SQL Server Management 17, which mean I have a server, So how do i get my SQL Connect Data Source? because afterward he uses it for
SqlDataAdapter sda = new SqlDataAdapter("select count(*) from login where username ='" + textBox1.Text + "' and password='" + textBox2.Text + "'", conn);
Any clue ?

Inside your project, in VS, connect to the server. Once you are on the server explorer, right click on the database to get the connection string. When you check the properties for the database, you should be able to see it.
You cannot get the connection string from SSMS, though you can get all the information for the connection string. Then, you can use those information to create your own connection string using this website: https://www.connectionstrings.com/ Just check which is better suited for you.

Microsoft Visual Studio SQL server connection - invalid pointer

So, I want to create a SQL database in Microsoft SQL Management Studio and connect it to Microsoft Visual Studio. I linked the database to Visual Studio and it worked. Now, I want to open that connection to test it with a button on a windows form application. Every time I try, it says "invalid pointer" but the database name is correct. I don't know what is wrong.
I still get the invalid pointer error...My instance name is DESKTOP-BJSAO6B but it doesnt seem to work...

You need provide a proper connection string like
string connectionString =
"data source=.\SQLEXPRESS;initial catalog=student;integrated security=True;";
using (SqlConnection connection =
new SqlConnection(connectionString))
{
connection.Open();
MessageBox.Show("You are connected");
}
where SQLEXPRESS - name your MSSQL instance ( may be different). More you can see here

For Ex:
string connectionString = "Data Source=Server-Name; Initial Catalog= Database-Name;Integrated Security=True"; //If you are using a local Database.
SqlConnection conn = new SqlConnection(connectionString);
conn.Open();
MessageBox.Show("You are connected");

Not inserting data into database and not getting any error

I am not sure what I am doing wrong, If I use the connection string shown here, my application works fine.
SqlConnection conn = new SqlConnection();
string DbPath = Application.StartupPath;
DbPath = DbPath.Substring(0, DbPath.LastIndexOf("\\bin"));
DbPath = DbPath + "\\MyDatabase.mdf";
conn.ConnectionString = "Data Source=.\\EXPRESS2008;AttachDbFilename=" + DbPath + ";Integrated Security=True;User Instance=True";
but if I use connection string here, it's not inserting data into MyDatabase table
conn.ConnectionString = Properties.Settings.Default.MyDatabaseConnectionString;
My app.config is
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<connectionStrings>
<add name="ERPSystem.Properties.Settings.MyDatabaseConnectionString"
connectionString="Data Source=.\EXPRESS2008; AttachDbFilename=|DataDirectory|\MyDatabase.mdf;Integrated
Security=True;User Instance=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
INSERT statement and preceding code:
comm = new SqlCommand("CreateUser", MyConnection.MyConn("Open"));
comm.CommandType = CommandType.StoredProcedure;
comm.Parameters.Add("#UserName", SqlDbType.VarChar).Value = userName.Text;
comm.Parameters.Add("#Password", SqlDbType.VarChar).Value = userPassword.Text;
comm.Parameters.Add("#UserRole", SqlDbType.VarChar).Value = UserRole.SelectedItem.ToString();
comm.ExecuteNonQuery();
This is the code to get the connection
class MyConnection
{
public static SqlConnection MyConn(string str)
{
SqlConnection conn = new SqlConnection();
try
{
//get application path
string DbPath = Application.StartupPath;
if (Program.RunFrEn == true) //bool var
//remove string after bin folder
DbPath = DbPath.Substring(0, DbPath.LastIndexOf("\\bin"));
//add database name with new path
DbPath = DbPath + "\\MyDatabase.mdf";
//generate new connection string for database
conn.ConnectionString = "Data Source=.\\EXPRESS2008;AttachDbFilename="
+ DbPath
+ ";Integrated Security=True;User Instance=True";
//conn.ConnectionString = Properties.Settings.Default.MyDatabaseConnectionString;
if (str == "Open")
{
if (conn.State == ConnectionState.Closed)
conn.Open();
}
else
{
if (conn.State == ConnectionState.Open)
conn.Close();
}
}
catch (System.Data.SqlClient.SqlException ex)
{
MessageBox.Show(ex.Message);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
return conn;
}
}
I am not getting any error
Thank you

The whole AttachDbFileName= approach is flawed - at best! When running your app in Visual Studio, it will be copying around the .mdf file (from your App_Data directory to the output directory - typically .\bin\debug - where you app runs) and most likely, your INSERT works just fine - but you're just looking at the wrong .mdf file in the end!
If you want to stick with this approach, then try putting a breakpoint on the myConnection.Close() call - and then inspect the .mdf file with SQL Server Mgmt Studio Express - I'm almost certain your data is there.
The real solution in my opinion would be to
install SQL Server Express (and you've already done that anyway)
install SQL Server Management Studio Express
create your database in SSMS Express, give it a logical name (e.g. MyDatabase)
connect to it using its logical database name (given when you create it on the server) - and don't mess around with physical database files and user instances. In that case, your connection string would be something like:
Data Source=.\\SQLEXPRESS;Database=MyDatabase;Integrated Security=True
and everything else is exactly the same as before...
Also see Aaron Bertrand's excellent blog post Bad habits to kick: using AttachDbFileName for more background info.

I also had fighted long time with same problem. And I saw many same questions & answers.
You're using |DataDirectory|. I assume you can get values from the DB file and you don't get error to run insert command but the values are not inserted into the DB file.
This is absolutely my private idea and my private conclusion is that this behavior is normal as |DataDirectory| does. I mean a data file of an application should be protected from manipulation once after deployment. The 'Data' file should provide data inside the file so that we can read the data.
Therefore, I coded to create a localDB .MDF file (SQL Server 2014) from users' side so that my applications can utilize the localDB to write and read data. My application automatically downloads data from cloud server which are we need to update frequently. On the other side, I put big and already fixed data into |DataDirectory| .MDF file, I mean inserted big data for read only and add the .MDF file to my project before deployment.
Hope my experience helps.. But, please keep in mind again that this is really my private opinion and I might be totally wrong and my experience is limited only to localDB. But again, I couldn't find a Microsoft's official document mentioning this behavior.
Do you have only 1 option like |DataDirectory|? Did this work to insert before? Is this code by you wrote on your own? If possible, try to find another option rather than |DataDirectory| to connect to the SQL Server database. I use a cloud SQL server with IP address but I can't understand why you use |DataDirectory|. There might be many various options as connection strings to SQL Server Express.

ConnectionString Database c#

I am create a database utility and I seem to not be able to get my connectionstring correct.
SqlConnection conn = new SqlConnection();
conn.ConnectionString =
"Data Source=.\\SQLExpress;" +
"User Instance=true;" +
"Integrated Security=true;" +
"AttachDbFilename=|DataDirectory|ConfigurationData.mdf;";
I believe this is in the correct format. As for the data source, my sql server is SQLExpress which runs sql server 2008 R2. My database is named ConfigurationData. Am I missing something?
When I run it, it opens the database - I assume it does since it does not through exception - but when I try inserting into a table, it does not actually insert it yet it executes the command.
conn.Open();
try
{
SqlCommand comm = new SqlCommand("INSERT INTO Test " + "(id,number) " + " VALUES(" + 10 + " , " + 12 + ")", conn);
comm.ExecuteNonQuery();
Console.WriteLine("Database is created successfully", "MyProgram");
}
catch (Exception ex)
{
}
finally
{
if ((conn.State == ConnectionState.Open))
{
conn.Close();
}
}

EDIT
Just remembered that I had answered a similar question a while back. Check it out:
Why can't I insert data into local database (SQL Compact Edition) with C#?
I don't think it is the connection string issue. But for your reference, a good site to refer to is http://www.connectionstrings.com/sql-server-2008/
You would need one of these:
Attach a database file, located in the data directory, on connect to a local SQL Server Express instance
Server=.\SQLExpress;AttachDbFilename=|DataDirectory|mydbfile.mdf;Database=dbname;
Trusted_Connection=Yes;
Attach a database file on connect to a local SQL Server Express instance
Server=.\SQLExpress;AttachDbFilename=C:\MyFolder\MyDataFile.mdf;Database=dbname;
Trusted_Connection=Yes;
Using an User Instance on a local SQL Server Express instance
The User Instance functionality creates a new SQL Server instance on the fly during connect. This works only on a local SQL Server instance and only when connecting using windows authentication over local named pipes. The purpose is to be able to create a full rights SQL
Server instance to a user with limited administrative rights on the computer.
Data Source=.\SQLExpress;Integrated Security=true;
AttachDbFilename=C:\MyFolder\MyDataFile.mdf;User Instance=true;
To use the User Instance functionality you need to enable it on the SQL Server. This is done by executing the following command: sp_configure 'user instances enabled', '1'. To disable the functionality execute sp_configure 'user instances enabled', '0'.

try (local) instead of dot, dot is not recognized in Win XP
conn.ConnectionString =
"Data Source=(local)\\SQLExpress;" +
"User Instance=true;" +
"Integrated Security=true;" +
"AttachDbFilename=|DataDirectory|ConfigurationData.mdf;";

You're SQL Statement isn't right also, and you should use parameters, but here is what you should have
SqlCommand comm = new SqlCommand("INSERT INTO Test (id, number) VALUES('" + 10 + " ', '" + 12 + "')", conn);

Why not just use the SqlConnectionStringBuilder class?:
SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder();
builder.DataSource = #"(local)\SQLExpress";
builder.UserInstance = true;
builder.IntegratedSecurity = true;
builder.AttachDBFilename = "|DataDirectory|ConfigurationData.mdf";
SqlConnection conn = new SqlConnection(builder.ConnectionString());
The output:
"Data Source=(local)\\SQLExpress;AttachDbFilename=|DataDirectory|ConfigurationData.mdf;Integrated Security=True;User Instance=True"

One of the way to do this is to add your connection string in web.config file as shown below:
Jus click on the properties of database on the database explorer. There you will find connectionstring in its properties. Jus add it in connectionstring below.
<configuration>
<connectionStrings>
<add name="ConnectionName" connectionString="your connection string" providerName="System.Data.SqlClient"/>
</connectionStrings>
</configuration>
Then in the page you can store it in string or directly refer to your connection as shown below:
Connection con=new SqlConnection();
con.ConnectionString=ConfigurationManager.ConnectionStrings["connString"].ToString();
and I suspect your insert statement is not properly declared.
Just try this:
SqlCommand comm = new SqlCommand("INSERT INTO Test (id,number) VALUES('10' ,'12')", con);
That's all from my part... Hope it helped you..

Connecting to local SQL Server database using C#

Suppose I have created a SQL Server database called Database1.mdf in the App_Data folder in Visual Studio with a table called Names.
How could I establish a connection to read the table values using C#?
So far I've tried something like this:
SqlConnection conn = new SqlConnection("Server=localhost;Database=Database1;");
conn.Open();
// create a SqlCommand object for this connection
SqlCommand command = conn.CreateCommand();
command.CommandText = "Select * from Names";
But I get an error:
database not found/error connecting to database

In Data Source (on the left of Visual Studio) right click on the database, then Configure Data Source With Wizard. A new window will appear, expand the Connection string, you can find the connection string in there

If you use SQL authentication, use this:
using System.Data.SqlClient;
SqlConnection conn = new SqlConnection();
conn.ConnectionString =
"Data Source=.\SQLExpress;" +
"User Instance=true;" +
"User Id=UserName;" +
"Password=Secret;" +
"AttachDbFilename=|DataDirectory|Database1.mdf;"
conn.Open();
If you use Windows authentication, use this:
using System.Data.SqlClient;
SqlConnection conn = new SqlConnection();
conn.ConnectionString =
"Data Source=.\SQLExpress;" +
"User Instance=true;" +
"Integrated Security=true;" +
"AttachDbFilename=|DataDirectory|Database1.mdf;"
conn.Open();

If you're using SQL Server express, change
SqlConnection conn = new SqlConnection("Server=localhost;"
+ "Database=Database1;");
to
SqlConnection conn = new SqlConnection("Server=localhost\SQLExpress;"
+ "Database=Database1;");
That, and hundreds more connection strings can be found at http://www.connectionstrings.com/

SqlConnection c = new SqlConnection(#"Data Source=localhost;
Initial Catalog=Northwind; Integrated Security=True");

You try with this string connection
Server=.\SQLExpress;AttachDbFilename=|DataDirectory|Database1.mdf;Database=dbname; Trusted_Connection=Yes;

I like to use the handy process outlined here to build connection strings using a .udl file. This allows you to test them from within the udl file to ensure that you can connect before you run any code.
Hope that helps.

Visual Studio 2019 (and probably a few previous versions).
View -> SQL Server Object Explorer
Top of the tree is 'SQL Server'
Under 'SQL Server', are couple of '(localdb)....'
Expand the (localdb)... -> Databases until you find your db.
Database Name (eg. Database1) -> Right-click -> Properties, and scroll the many properties (eg. "ANSI
NULL Default"). Find the "Connection string" property, copy the value
into your code, and you're running.