[Serializable()]

        //Create a subclass inheriting BaseFilterItem class.
        public class CustomFilter : FarPoint.Win.Spread.BaseFilterItem
        {
            
            FarPoint.Win.Spread.SheetView sv = null;
            public CustomFilter()
            {
            }

            public CustomFilter(FarPoint.Win.Spread.SheetView sheetView)
            {
                this.sv = sheetView;
            }

            //---------------------------------------------------------
            //Return names to be displayed in the drop-down list.
            //---------------------------------------------------------
            public override string DisplayName
            {
                get { return "Extract any values that are greater than 10 and less than 50."; }
            }

            //-----------------------------------------------------------------------------------------
            //Set sheets to filters.
            //-----------------------------------------------------------------------------------------
            public override FarPoint.Win.Spread.SheetView SheetView
            {
                set { sv = value; }
            }

            //-----------------------------------------------------------------------------------------
            //Evaluate specified values by conditions.
            //-----------------------------------------------------------------------------------------
            public bool IsFilteredIn(int value)
            {
                if (!(value == null) & (value >= 10) & (value <= 50))
                {
                    //Return True only when the following conditions are satisfied.
                    //(1)Values are entered.
                    //(2)Values are not lower than 10.
                    //(3)Values are not greater than 50.
                    return true;
                }
                return false;
            }

            //-----------------------------------------------------------------------------------------
            //Display names returned by DisplayName property.
            //-----------------------------------------------------------------------------------------
            public override bool ShowInDropDown(int columnIndex, int[] filteredInRowList)
            {
                return true;
            }

            //-----------------------------------------------------------------------------------------
            //Execute filtering in the column specified in a sheet.
            //-----------------------------------------------------------------------------------------
            public override int[] Filter(int columnIndex)
            {

                System.Collections.ArrayList list = new System.Collections.ArrayList();
                int[] returnList = null;
                int row = 0;

                if ((sv == null))
                {
                    return returnList;
                }

                for (row = 0; row <= sv.RowCount - 1; row++)
                {
                    if (!(sv.GetValue(row, columnIndex) == null))
                    {
                        int value = (int)sv.GetValue(row, columnIndex);
                        if (IsFilteredIn(value))
                        {
                            //Add row indexes that meet conditions sequentially.
                            list.Add(row);
                        }
                    }
                }

                //When there are any rows that meet conditions, copy them to arrays.
                if (list.Count > 0)
                {
                    returnList = new int[list.Count];
                    list.CopyTo(returnList);
                    list.Clear();
                }

                //Return all row indexes that meet conditions.
                return returnList;

            }

            //-----------------------------------------------------------------------------------------
            //When any data that has to be serialized is included in a custom filter class, override it.
            //-----------------------------------------------------------------------------------------
            public override bool Serialize(System.Xml.XmlTextWriter w)
            {

                w.WriteStartElement("CustomFilter");
                base.Serialize(w);
                w.WriteEndElement();
                return true;
            }

            public override bool Deserialize(System.Xml.XmlNodeReader r)
            {

                if (r.NodeType == System.Xml.XmlNodeType.Element)
                {
                    if (r.Name.Equals("CustomFilter"))
                    {
                        base.Deserialize(r);
                    }
                }
                return true;

            }

        }


private void Form1_Load(object sender, EventArgs e)
        {           
    //Display only custom filters created in Column1.
   FarPoint.Win.Spread.FilterColumnDefinition fcd = new FarPoint.Win.Spread.FilterColumnDefinition(0, FarPoint.Win.Spread.FilterListBehavior.Custom);
   FarPoint.Win.Spread.HideRowFilter hf = new FarPoint.Win.Spread.HideRowFilter(fpSpread1.ActiveSheet);
   hf.AddColumn(fcd);
   fpSpread1.ActiveSheet.RowFilter = hf;

   //Add the custom filter created for Column1.
   CustomFilter cfi = new CustomFilter(fpSpread1.ActiveSheet);
   FarPoint.Win.Spread.FilterColumnDefinition ccd = fpSpread1.ActiveSheet.RowFilter.GetFilterColumnDefinition(0);
   ccd.Filters.Add(cfi);

   fpSpread1.ActiveSheet.DefaultStyle.CellType = new FarPoint.Win.Spread.CellType.NumberCellType();
   fpSpread1.ActiveSheet.SetValue(0, 0, 10);
   fpSpread1.ActiveSheet.SetValue(1, 0, 100);
   fpSpread1.ActiveSheet.SetValue(2, 0, 50);
   fpSpread1.ActiveSheet.SetValue(3, 0, 40);
   fpSpread1.ActiveSheet.SetValue(4, 0, 80);
   fpSpread1.ActiveSheet.SetValue(5, 0, 1);
   fpSpread1.ActiveSheet.SetValue(6, 0, 65);
   fpSpread1.ActiveSheet.SetValue(7, 0, 20);
   fpSpread1.ActiveSheet.SetValue(8, 0, 30);
   fpSpread1.ActiveSheet.SetValue(9, 0, 35);   
        }