<connectionStrings>
    <add name="FaribaEntities" connectionString="metadata=res://*/Classes.MyWorkShopModel.csdl|res://*/Classes.MyWorkShopModel.ssdl|res://*/Classes.MyWorkShopModel.msl;provider=System.Data.SqlClient;provider connection string="Data Source=.SQLEXPRESS;AttachDbFilename=|DataDirectory|Fariba.MDF;Integrated Security=true;User Instance=True;MultipleActiveResultSets=True"" providerName="System.Data.EntityClient"/>
</connectionStrings>

string Connection_String= ConfigurationManager.ConnectionStrings["FaribaEntities"].ToString();

SqlConnection con1 = new SqlConnection();
con1.ConnectionString = Connection_String;
con1.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = con1;
cmd.CommandText = "Select name from Users where(code = '1')";
cmd.ExecuteNonQuery();
con1.Close();

con1.ConnectionString = "Server= ... ";