SQL Express Connection String: Mdf File Location Relative to Application Location

SQL Express connection string: mdf file location relative to application location

Thanks everyone, I used a combination of your responses.

In my app.config file my connection string is defined as follows

<add name="MyConnectionString"
    connectionString="Server=.\SQLExpress;AttachDbFilename=|DataDirectory|\MyDatabase.mdf;Database=MyDatabaseForTesting;Trusted_Connection=Yes;" />

In my unit test class I set the DataDirectory property using the following

[TestInitialize]
public void TestInitialize()
{
    AppDomain.CurrentDomain.SetData("DataDirectory", System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Databases"));

    // rest of initialize implementation ...
}

C# Visual Studio: |DataDirectory| keyword in connection string conflicts mdf files

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

1. install SQL Server Express (and you've already done that anyway)

2. install SQL Server Management Studio Express

3. create your database in SSMS Express, give it a logical name (e.g. systemdb)

4. 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=systemdb;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.

Relative path connection string vb.net

The DataDirectory value is just a string extracted from the AppDomain.CurrentDomain property list. In a WinForm application is not pre-defined but you could set it before opening your database.

AppDomain.CurrentDomain.SetData("DataDirectory", @"C:\MyReadWriteFolder")

then the connection string with AttachDbFilename=|DataDirectory|\Food_CustomerDB.mdf should works provided you put the database there (C:\MyReadWriteFolder).

Connection String to Connect to .MDF

If you're using the *.mdf file in the App_Data folder of an ASP.NET app you can use this.

Server=.\SQLExpress;AttachDbFilename=|DataDirectory|mydbfile.mdf;Database=dbname; Trusted_Connection=Yes;

If it's not an ASP.NET application don't use the DataDirectory syntax and just use the full c:\... path.

connection string for SQL database by path For Desktop Application

Server=.\SQLExpress;AttachDbFilename=C:\MyFolder\MyDataFile.mdf;Database=dbname;
Trusted_Connection=Yes;

Best place to find Connection strings

How is location of |Data Directory| in connection strings resolved?

Here is the code which specifies where is |DataDirectory|

GetDataDirectory

[PermissionSet(SecurityAction.Assert, Unrestricted = true)]
internal static string GetDataDirectory() {
    if (HostingEnvironment.IsHosted)
        return Path.Combine(HttpRuntime.AppDomainAppPath, HttpRuntime.DataDirectoryName);

    string dataDir = AppDomain.CurrentDomain.GetData(s_strDataDir) as string;
    if (string.IsNullOrEmpty(dataDir)) {
        string appPath = null;

#if !FEATURE_PAL // FEATURE_PAL does not support ProcessModule
        Process p = Process.GetCurrentProcess();
        ProcessModule pm = (p != null ? p.MainModule : null);
        string exeName = (pm != null ? pm.FileName : null);

        if (!string.IsNullOrEmpty(exeName))
            appPath = Path.GetDirectoryName(exeName);
#endif // !FEATURE_PAL

        if (string.IsNullOrEmpty(appPath))
            appPath = Environment.CurrentDirectory;

        dataDir = Path.Combine(appPath, HttpRuntime.DataDirectoryName);
        AppDomain.CurrentDomain.SetData(s_strDataDir, dataDir, new FileIOPermission(FileIOPermissionAccess.PathDiscovery, dataDir));
    }

    return dataDir;
}

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