ConnectionStringsProvider

ConnectionStringsProvider.cs

using System;
using System.Configuration;

static class ConnectionStringsProvider
{
    static ConnectionStringSettings _connectionString;

    public static ConnectionStringSettings Get()
    {
        if (_connectionString == null)
        {
            string connectionStringName = "YourDbName";

            string localConnectionStringName = connectionStringName + "@" + Environment.MachineName;

            ConnectionStringSettings connectionString = GetConnectionString(localConnectionStringName);

            _connectionString = connectionString ?? GetConnectionString(connectionStringName);
        }

        return _connectionString;
    }

    static ConnectionStringSettings GetConnectionString(string name)
    {
        return ConfigurationManager.ConnectionStrings[name];
    }
}

web.config

<connectionStrings>
  <add name="YourDbName" connectionString="Data Source=.;Initial Catalog=YourDbName;" />
  <add name="YourDbName@czarek" connectionString="Data Source=.;Initial Catalog=YourDbName;" />
  <add name="YourDbName@jarek" connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=YourDbName;" />
  <add name="YourDbName@arek" connectionString="Data Source=(local)\SqlServer;Initial Catalog=YourDbName;" />
</connectionStrings>