How do I connect to an MDF database file?

Question

I'm experimenting in connecting a C# app to an MDF database for the first time, and I need a little help ..

I made a small MDF database file in Visual Studio 2010, then created another project and imported the file into the project itself.

I am not trying to connect to the MDF file via code. Here the code I'm using:

namespace DBtestApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        System.Data.SqlClient.SqlConnection con;
        private void Form1_Load(object sender, EventArgs e)
        {
            con = new System.Data.SqlClient.SqlConnection();
            con.ConnectionString = "DataSource=.\\SQLEXPRESS; AttachDbFilename =SampleDatabase.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True";
            con.Open();
            MessageBox.Show("Connection opened");
            con.Close();
            MessageBox.Show("Connection closed");
        }
    }
}

When I run the application, I get an exception at the line where I define the connection string, and the exception has this message at the top of the stack:

System.ArgumentException: Keyword not supported: 'datasource'.

Can someone point me in the right direction ?

this post might help: [How do I connect to an .mdf (Microsoft SQL Server Database File) in a simple web project?][1] Cheerz [1]: stackoverflow.com/questions/173209/… — Helikaon
– Helikaon, Commented Jan 19, 2012 at 13:11

KV Prajapati · Accepted Answer · 2013-10-25 04:35:31Z

34

Add space between Data Source

 con.ConnectionString = @"Data Source=.\SQLEXPRESS;
                          AttachDbFilename=c:\folder\SampleDatabase.mdf;
                          Integrated Security=True;
                          Connect Timeout=30;
                          User Instance=True";

edited Oct 25, 2013 at 4:35

answered Jan 19, 2012 at 13:14

KV Prajapati

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7 Comments

Henk Holterman Over a year ago

And while you're editing, remove the spaces in ; AttachDbFilename =

Ahmad Over a year ago

Tried it, but now I got the following exception:

System.Data.SqlClient.SqlException (0x80131904): An attempt to attach an auto-named database for file SampleDatabase.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.

KV Prajapati Over a year ago

You need to specify the path of sampleDatabase.mdf. Have a look at edited post.

Ahmad Over a year ago

But why should I specify the complete path when I've added the MDF file to the project's local resources ? .. I don't want to hardcode a path as that would mean that MDF file always has to be there .. Can I not reference to its local presence within the project ?

jamesmortensen Over a year ago

I was thinking of editing this so that the string was concatenated to eliminate the horizontal scroll, but I'm afraid I don't know enough about this to trust myself not to make the answer incorrect.

|

Mahmmoud Qassem · Accepted Answer · 2016-11-16 08:17:04Z

27

Go to server explorer > Your Database > Right Click > properties > ConnectionString and copy the connection string and past the copied to connectiongstring code :)

answered Nov 16, 2016 at 8:17

Mahmmoud Qassem

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2 Comments

Stas Ivanov Over a year ago

One of the best answers I've seen so far :)

Patrick Kelly Over a year ago

This will break the moment you try it on another machine. While that connection string is valid for your machine, if you take a moment to read it you'll notice that it has the path hardcoded.

user1943915 · Accepted Answer · 2013-12-13 18:21:27Z

10

string sqlCon = @"Data Source=.\SQLEXPRESS;" +
                @"AttachDbFilename=|DataDirectory|\SampleDB.mdf;
                Integrated Security=True;
                Connect Timeout=30;
                User Instance=True";
SqlConnection Con = new SqlConnection(sqlCon);

The filepath should have |DataDirectory| which actually links to "current project directory\App_Data\" or "current project directory" and get the .mdf file.....Place the .mdf in either of these places and should work in visual studio 2010.And when you use the standalone application on production system, then the current path where the executable file is, should have the .mdf file.

edited Dec 13, 2013 at 18:21

answered Dec 13, 2013 at 18:15

user1943915

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Comments

July.Tech · Accepted Answer · 2017-08-31 18:25:04Z

8

For Visual Studio 2015 the connection string is:

"Data Source=(localdb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|Database1.mdf;Integrated Security=True"

answered Aug 31, 2017 at 18:25

July.Tech

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1 Comment

BrianLegg Over a year ago

This was the only thing that worked for me with an MDF. I'm using VS2019 with .Net Core 3.

John Woo · Accepted Answer · 2012-01-19 13:14:24Z

1

Server=.\SQLExpress;AttachDbFilename=c:\mydbfile.mdf;Database=dbname; Trusted_Connection=Yes;

answered Jan 19, 2012 at 13:14

John Woo

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1 Comment

Ahmad Over a year ago

I tried this modified version" "Server=.\\SQLExpress;AttachDbFilename=SampleDatabase.mdf;Database=SampleDatabase; Trusted_Connection=Yes", and got the following exception:

System.Data.SqlClient.SqlException (0x80131904): A file activation error occurred. The physical file name 'SampleDatabase.mdf' may be incorrect. Diagnose and correct additional errors, and retry the operation. Cannot attach the file 'SampleDatabase.mdf' as database 'SampleDatabase'.

OldBuildingAndLoan · Accepted Answer · 2021-06-28 12:50:50Z

1

Alternative solution, where you can have the database in the folder you want inside the solution. That worked for me:

.ConnectionString(@"Data Source=(LocalDB)\MSSQLLocalDB;
                    AttachDbFilename="+AppDomain.CurrentDomain.BaseDirectory+"Folder1\\Folder2\\SampleDatabase.mdf" + ";
                    Integrated Security=True;")

edited Jun 28, 2021 at 12:50

OldBuildingAndLoan

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answered Oct 18, 2017 at 16:55

f4d0

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lava · Accepted Answer · 2022-12-14 08:09:00Z

1

Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename="C:\Users\hasif\Documents\Visual Studio 2015\Projects\vgsoft\SqlserverRepo\data\Database1.mdf";Integrated Security=True;Connect Timeout=30

1

2 ConnectionString

answered Dec 14, 2022 at 8:09

lava

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Mike James · Accepted Answer · 2014-06-11 11:45:04Z

0

SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=E:\Samples\MyApp\C#\bin\Debug\Login.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True");

this is working for me... Is there any way to short the path? like

SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=\bin\Debug\Login.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True");

answered Jun 11, 2014 at 11:45

Mike James

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