The System.Web.Compilation.ConnectionStringsExpressionBuilder class provides access to values in the <connectionStrings> section of the Web.config file. The <connectionStrings> section of the Web.config file contains connection string values in name/value pairs.

A connection string value is retrieved by assigning an expression of the form

<%$ ConnectionStrings: secureConnectionString %>

to a control property. The part of the expression before the colon (:) designates the type of expression to be retrieved, and the part after the colon signifies the name of the connection string. The preceding expression would retrieve the following value from the Web.config file.

<connectionStrings>

<add name="secureConnectionString" connectionString="Data

Source=localhost;Integrated Security=SSPI;Initial

Catalog=Northwind;" providerName="System.Data.SqlClient" />

</connectionStrings>

When the page parser encounters an expression with the prefix ConnectionStrings, it creates an instance of the System.Web.Compilation.ConnectionStringsExpressionBuilder class to handle the expression.

If the expression is encountered in a page that will be compiled, the System.Web.Compilation.ConnectionStringsExpressionBuilder object generates code that retrieves the specified connection string from the Web.config file. If the expression is encountered in a page that will not be compiled, the System.Web.Compilation.ConnectionStringsExpressionBuilder object returns the value from the Web.config file when the page is parsed.