You could do with with .Contains like this:
if(new[]{BillType.Receipt,BillType.Bill,BillType.Payment}.Contains(type)){}
Or, create your own extension method that does it with a more readable syntax
public static class MyExtensions
{
public static bool IsIn<T>(this T @this, params T[] possibles)
{
return possibles.Contains(@this);
}
}
Then call it by:
if(type.IsIn(BillType.Receipt,BillType.Bill,BillType.Payment)){}