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How to automatically attach SQL Server database in C#?

I am new to C# and SQL Server 2014 Express and I am using Windows forms.
I am building the small application which read/write from/to SQL Server database.
I am trying to automatically attach SQL Server database, then read data from a table named Test_Table and then fill a Datagridview.
The code I used:
SqlConnection MyConnection = new SqlConnection(ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString);
SqlCommand MyCommand= new SqlCommand();
DataTable DataTable = new DataTable();
SqlDataAdapter Sql_Data_Adapter= new SqlDataAdapter();
private void button1_Click(object sender, EventArgs e)
{
MyConnection.Open();
MyCommand.CommandText = "SELECT * FROM Test_Table ";
MyCommand.Connection = MyConnection;
Sql_Data_Adapter.SelectCommand = MyCommand;
Sql_Data_Adapter.Fill(DataTable);
dataGridView1.DataSource = DataTable;
MyCommand.Parameters.Clear();
Sql_Data_Adapter.Dispose();
MyConnection.Close();
}
App.config:
<connectionStrings>
<add name="MyConnectionString"
connectionString="Data Source=localhost; AttachDbFilename=D:\\DB\\MyDB.mdf;Integrated Security=True"/>
</connectionStrings>
When I click on button1 it throws an error:
An attempt to attach an auto-named database for file D:\DB\MyDB.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.
I have no other databases attached and the database path is correct.
I had a look here, here and here but non of them helped.
Any idea how can I automatically attach a SQL Server database file? Thank you

What is the version of SQL Server are you using? This will explain a lot about your error message.
Your Connection String:
"Data Source=localhost; AttachDbFilename=D:\DB\MyDB.mdf;Integrated
Security=True"
You can only use AttachDbFilename with SQL Express. In your connection string, the Data Source is set to localhost. That sounds like you have a full version SQL Server installed.
If you have a full version of SQL Server installed, you can only attach a database via Management Studio.
If you are using SQL Express, change your data source:
Data Source=.\SQLEXPRESS

Retrieve data from LocalDB in ASP.NET webforms

I am using a simple webforms application to retrieve data to bind in a GridView control from LocalDb\v11.0 locally. I have created MyDb.sdf and a table named info inside App_Data folder. I am getting the following error
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)
Web.config:
<connectionStrings>
<add name="dbcs"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFileName=|DataDirectory|\MyDb.sdf;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
HTML
<form id="form1" runat="server">
<div>
<asp:GridView ID="GridView1" runat="server"></asp:GridView>
</div>
</form>
Back-end Code
protected void Page_Load(object sender, EventArgs e)
{
string con = WebConfigurationManager.ConnectionStrings["dbcs"].ConnectionString;
using (SqlConnection scon = new SqlConnection(con))
{
SqlCommand cmd = new SqlCommand("select * from info", scon);
scon.Open();
GridView1.DataSource = cmd.ExecuteReader();
GridView1.DataBind();
scon.Close();
}
}

Your connection string and code (using SqlConnection) is for a full-blown version of SQL Server (Express, Web, Standard, Enterprise), while the .sdf database file is for SQL Server Compact Edition.
Those two technologies are NOT compatible. You cannot attach a .sdf database file to your (LocalDB)\v11.0 LocalDB instance - it needs to be a .mdf file.
Either use a real SQL Server (create a database in your SQL Server instance) and your current code - or then you need to switch to using SqlCeConnection and SqlCeCommand in your code

Getting my sql database to work with my hit counter code in asp.net

I been trying to follow this tutorial to create a hit counter for my website using asp.net/c# and html/css. I'm running this off localhost. I'm having trouble configuring or getting the sql database connectionstring to work. Here is a link to the tutorial I'm using Hit counter in asp.net. So I follow the tutorial and run the code, and i get this error
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: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)
I'm pretty sure it has to do with how i wrote the ConnectionString in the web Config file. Maybe I'm pointing the data source to the wrong place? Maybe it's because i'm not using Initial Catalog in the connection string?
connectionstring in my web config file:
<connectionStrings>
<add name="ConnectionString" connectionString="Data
Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;
Integrated Security=True;User Instance=True"
providerName="System.Data.SqlClient"/>
</connectionStrings>
calling my connectionstring from .cs file
/objects we will need to work with the db
SqlConnection conn;
SqlCommand cmd;
//IF PAGE IS NOT A POSTBACK, ADD A HIT
if (!Page.IsPostBack)
{
//connect to the db
conn = new
SqlConnection(WebConfigurationManager.ConnectionStrings
["ConnectionString"].ConnectionString);
//the sql command to increment hits by 1
cmd = new SqlCommand("UPDATE Hits SET Hits = Hits+1 WHERE
Name=#Name", conn);
cmd.CommandType = CommandType.Text;
//update where Name is 'About' which corresponds to this page
cmd.Parameters.AddWithValue("#Name", "About");
using (conn)
{
//open the connection
conn.Open();
//send the query
cmd.ExecuteNonQuery();
}
I'm still a newbie when it comes to all this database stuff, any help be appreciated.
update fixed: I followed the instructions by user1551066 and found my data source for the database.mdf and then i plugged it in my connectionstring in web config and it WORKED.
<connectionStrings>
<add name="ConnectionString" connectionString="Data Source=
(LocalDB)\v11.0;AttachDbFilename=C:\Users\bobdole\Desktop
\VideoWebsite\VideoWebsite\VideoWebsite\App_Data\Database.mdf;
Integrated Security=True;" providerName="System.Data.SqlClient"/>
</connectionStrings>

Try to connect to your .mdf database in visual studio. 1)Go to server explorer tab. 2)You should see your database .mdf file (possibly as DefaultConnection) 3) Click on it. In the Properties window you wil see the section Connection. Unfold it and you will see the ConnectionString property. Copy and paste it in your web.config ConnectionString setting.

Your error is due to SQL connection failure.Please check the connection string which you have passed was correct.For connection string reference please refer here.
Sql Server connection string
connetionString="Data Source=ServerName;
Initial Catalog=DatabaseName;User ID=UserName;Password=Password"
If you have a named instance of SQL Server, you'll need to add that as well.
"Server=localhost\sqlexpress"
and for connecting SQL Server
string connetionString = null;
SqlConnection cnn ;
connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password"
cnn = new SqlConnection(connetionString);
try
{
cnn.Open();
MessageBox.Show ("Connection Open ! ");
cnn.Close();
}
catch (Exception ex)
{
MessageBox.Show("Can not open connection ! ");
}
Please refer [here][2]

Connecting to SQL Server using windows authentication

When I was trying to connect to SQL Server using the following code:
SqlConnection con = new SqlConnection("Server=localhost,Authentication=Windows Authentication, Database=employeedetails");
con.Open();
SqlCommand cmd;
string s = "delete employee where empid=103";
I get the following error:
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)

A connection string for SQL Server should look more like: "Server= localhost; Database= employeedetails; Integrated Security=True;"
If you have a named instance of SQL Server, you'll need to add that as well, e.g., "Server=localhost\sqlexpress"

Your connection string is wrong
<connectionStrings>
<add name="ConnStringDb1" connectionString="Data Source=localhost\SQLSERVER;Initial Catalog=YourDataBaseName;Integrated Security=True;" providerName="System.Data.SqlClient" />
</connectionStrings>

Check out www.connectionstrings.com for a ton of samples of proper connection strings.
In your case, use this:
Server=localhost;Database=employeedetails;Integrated Security=SSPI
Update: obviously, the service account used to run ASP.NET web apps doesn't have access to SQL Server, and judging from that error message, you're probably using "anonymous authentication" on your web site.
So you either need to add this account IIS APPPOOL\ASP.NET V4.0 as a SQL Server login and give that login access to your database, or you need to switch to using "Windows authentication" on your ASP.NET web site so that the calling Windows account will be passed through to SQL Server and used as a login on SQL Server.

You have to add a connectionString within your Web.config file as
<connectionStrings>
<add name="ASPNETConnectionString" connectionString="Data Source=SONU\SA;Initial Catalog=ASPNET;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
Then Write your SQL connection string as below:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
public partial class WebPages_database : System.Web.UI.Page
{
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ASPNETConnectionString"].ToString());
SqlDataAdapter da;
DataSet ds;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnAdmnNumber_Click(object sender, EventArgs e)
{
string qry = "select * from Table";
da = new SqlDataAdapter(qry, con);
ds = new DataSet();
da.Fill(ds);
GridView1.DataSource = ds;
GridView1.DataBind();
}
}
For more Information please follow this link
How To:Connect to SQl with windows Authentication
SQL Server with windows authentication

I was facing the same issue and the reason was single backslah.
I used double backslash in my "Data source" and it worked
connetionString = "Data Source=localhost\\SQLEXPRESS;Database=databasename;Integrated Security=SSPI";

This worked for me:
in web.config file;
<add name="connectionstring name " connectionstring="server=SQLserver name; database= databasename; integrated security = true"/>

Just replace the first line with the below;
SqlConnection con = new SqlConnection("Server=localhost;Database=employeedetails;Trusted_Connection=True");
Regards.

Use this code:
SqlConnection conn = new SqlConnection();
conn.ConnectionString = #"Data Source=HOSTNAME\SQLEXPRESS; Initial Catalog=DataBase; Integrated Security=True";
conn.Open();
MessageBox.Show("Connection Open !");
conn.Close();

use this code
Data Source=.;Initial Catalog=master;Integrated Security=True

How to connect to the Remote Database using Connection String in C#.net

every one. I want to connect a remote database using Sql Connection String in C#.net, I am trying it to do, but failed to connect. I am new to C#.net connections to the Database. Can any one pls tell me how to write the Connection String.

Check this website for the specific format: http://www.connectionstrings.com/

Here is a little bit of code that will connect to a dabase called myDatabase on a server called myServer, query the myTable table for the column myColumn, and insert the returned data into a list of strings.
While by no means exaustive or perfect, this snippet does show some of the core aspects of working with data in C#.
List<string> results = new List<string>();
SqlConnection conn = new SqlConnection("Data Source = myServerAddress; Initial Catalog = myDataBase; User Id = myUsername; Password = myPassword;");
using (SqlCommand command = new SqlCommand())
{
command.Connection = conn;
command.CommandType = CommandType.Text;
command.CommandText = "Select myColumn from myTable";
using (SqlDataReader dr = command.ExecuteReader())
{
while (dr.Read())
{
results.Add(dr["myColumn"].ToString());
}
}
}

There is no difference in this regard. The connection string to connect to remote server database is written same as you write to connect to local database server.
However, only Data Source changes.
Below is a sample connection string
User ID=dbUserName;Password=dbUserPwd;Initial Catalog=dbName;Data Source=remoteMachine\serverInstanceNameIfAny;
But by default sql server is not configured to Sql Server Authentication, so you need to enable
Sql server authentication
Also Create a Log in user in the database

Here are a couple of examples:
With Integrated Security
Server=RemoteMachineName\Intance; Initial Catalog=DatabaseName; Integrated Security=true;
With username and password
Server=RemoteMachineName\Intance; Initial Catalog=DatabaseName; UID=Username; PWD=Password;

You can also do that in web.config file
<configuration>
<ConnectionStrings>
<add name="YourConnectionString" connectionString="Data Source=Nameofserver;
InitialCatalog=NameofDatabase;Persist Security Info=True;
UserID=DatabaseUserID;Password=DatabasePassword" providerName="System.Data.SqlClient"/>
</connectionStrings>
</configuration>