public class BillsViewModel : ViewModelBase
	{
	   public SelectOptions SOptions { get;set;}= new SelectOptions();
		private List<Bills> _allBills;
		public RelayCommand GoButtonClicked { get; set; }

	public void GoFilterData(object param)
		{
			AllBills.Filter=FilterTask;
	     
		}
	public bool FilterTask(object value)
	{
	  bool f;
	  var entry = value as Bills;
	  
	  if (entry != null)
	  {
		if (!string.IsNullOrEmpty(FilterString))
		{
		  
          switch (SOptions.EnumProperty)
          {
			case Options.BillNo:
			      f = entry.Party == SelectedCBItem && entry.BillNo == FilterString;
			  break;
			case Options.BillDt:
			      f = entry.Party == SelectedCBItem && entry.BillDt == FilterString;
			  break;
			case Options.Amt:
			      f = entry.Party == SelectedCBItem && entry.Amt == FilterString;
			  break;
			default:
			  f = entry.Party == SelectedCBItem;

			  break;
		  }
		  
		  
		  return f;
		}
        else
        {
		    f = entry.Party == SelectedCBItem;
		  return f;
        }
		
	  }

	  return false;
	}
....

}