Public Enum UnderlineFontStyle 
   Inherits System.Enum

Dim instance As UnderlineFontStyle

public enum UnderlineFontStyle : System.Enum 

protected void Page_Load(object sender, System.EventArgs e)
        {
            FpSpread1.Sheets[0].Cells[0, 0].Value = 3;
            FpSpread1.Sheets[0].Cells[1, 0].Value = 2;
            FpSpread1.Sheets[0].Cells[1, 1].Value = 10;
            FpSpread1.Sheets[0].Cells[0, 2].Value = 1;              
        }

protected void Button1_Click(object sender, EventArgs e)
        {
            FarPoint.Web.Spread.UnaryComparisonConditionalFormattingRule unary = new FarPoint.Web.Spread.UnaryComparisonConditionalFormattingRule(FarPoint.Web.Spread.UnaryComparisonOperator.EqualTo, 10);
            unary.Operator = FarPoint.Web.Spread.UnaryComparisonOperator.EqualTo;
            unary.Value = 10;
            unary.BackColor = Color.Red;
            unary.FontStyle = new FarPoint.Web.Spread.SpreadFontStyle(FarPoint.Web.Spread.UnderlineFontStyle.Underline);
            unary.FontStyle.Underline = FarPoint.Web.Spread.UnderlineFontStyle.Underline;
            unary.FontStyle.Overline = FarPoint.Web.Spread.OverlineFontStyle.Overline;
            unary.FontStyle.Strikeout = FarPoint.Web.Spread.StrikeoutFontStyle.Strikeout;

            FarPoint.Web.Spread.BetweenValuesConditionalFormattingRule between = new FarPoint.Web.Spread.BetweenValuesConditionalFormattingRule(false, 1, false, 20, false);
            between.FirstValue = 1;
            between.SecondValue = 20;
            between.IsNotBetween = true;
            between.BackColor = Color.Bisque;

            //SetConditionalFormatting Overload
            FpSpread1.ActiveSheetView.SetConditionalFormatting(0, 0, 3, 3, false, unary, between);
        }

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        FpSpread1.Sheets(0).Cells(0, 0).Value = 3
        FpSpread1.Sheets(0).Cells(1, 0).Value = 2
        FpSpread1.Sheets(0).Cells(1, 1).Value = 10
        FpSpread1.Sheets(0).Cells(0, 2).Value = 1
    End Sub

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click      
        Dim unary As New FarPoint.Web.Spread.UnaryComparisonConditionalFormattingRule(FarPoint.Web.Spread.UnaryComparisonOperator.EqualTo, 10)
        unary.Operator = FarPoint.Web.Spread.UnaryComparisonOperator.EqualTo
        unary.Value = 10
        unary.BackColor = Drawing.Color.Red
        unary.FontStyle = New FarPoint.Web.Spread.SpreadFontStyle(FarPoint.Web.Spread.UnderlineFontStyle.Underline)
        unary.FontStyle.Underline = FarPoint.Web.Spread.UnderlineFontStyle.Underline
        unary.FontStyle.Overline = FarPoint.Web.Spread.OverlineFontStyle.Overline
        unary.FontStyle.Strikeout = FarPoint.Web.Spread.StrikeoutFontStyle.Strikeout

        Dim between As New FarPoint.Web.Spread.BetweenValuesConditionalFormattingRule(False, 1, False, 20, False)
        between.FirstValue = 1
        between.SecondValue = 20
        between.IsNotBetween = True
        between.BackColor = Drawing.Color.Bisque

        'SetConditionalFormatting Overload
        FpSpread1.ActiveSheetView.SetConditionalFormatting(0, 0, 3, 3, False, unary, between)
    End Sub