В global.asax.cs пишется
protected void Application_BeginRequest(Object sender, EventArgs e) {
System.Globalization.CultureInfo nf_info=new System.Globalization.CultureInfo("RU-ru",false);
nf_info.NumberFormat.NumberDecimalSeparator=".";
nf_info.NumberFormat.NumberGroupSeparator=" ";
nf_info.NumberFormat.CurrencyDecimalSeparator=".";
nf_info.NumberFormat.CurrencyGroupSeparator=" ";
System.Threading.Thread.CurrentThread.CurrentCulture = nf_info;

}