<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <connectionStrings>
        <add name="my_conn" connectionString="Data Source=xx.xx.xx.xxx;Initial Catalog=some_db;User ID=xxx;Password=yyy" />
    </connectionStrings>
</configuration>

// Assume failure.
string returnValue = null;

// Look for the name in the connectionStrings section.
ConnectionStringSettings settings = ConfigurationManager.ConnectionStrings["my_conn"];

// If found, return the connection string.
if (settings != null)
    returnValue = settings.ConnectionString;