How Can I Use the |DataDirectory| Substitution String in ADO.NET Connection Strings?

Leveraging the |DataDirectory| Placeholder in ADO.NET Connection Strings

While the |DataDirectory| parameter is readily available in your AppConfig file, comprehensive documentation can be scarce. This guide clarifies its usage.

Understanding the |DataDirectory| Placeholder

The |DataDirectory| placeholder acts as a dynamic path variable, allowing flexible database file location configuration. This dynamic approach proves invaluable for applications like web apps or multi-user systems requiring adaptable database paths.

Replacing Hardcoded Paths with |DataDirectory|

Let's illustrate with a connection string using a fixed database path:

<code class="language-csharp">SqlConnection c = new SqlConnection (
   @"Data Source=.\SQLDB; AttachDbFilename=C:\MyDB\Database.mdf;Initial Catalog=Master");</code>

Now, let's refactor this using the |DataDirectory| placeholder:

<code class="language-csharp">// Define the |DataDirectory| path at runtime
AppDomain.CurrentDomain.SetData("DataDirectory", "C:\myDB");

// Connection string utilizing the |DataDirectory| placeholder
SqlConnection c = new SqlConnection (
   @"Data Source=.\SQLDB; AttachDbFilename=|DataDirectory|\Database.mdf;Initial Catalog=Master");</code>

This revised approach allows you to alter the database location without needing to recompile your application, simply by adjusting the |DataDirectory| setting during runtime.

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