Public Property IsBlank As Boolean

Dim instance As BlankConditionalFormattingRule
Dim value As Boolean
 
instance.IsBlank = value
 
value = instance.IsBlank

public bool IsBlank {get; set;}

private void Form1_Load(object sender, 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;            
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //Blank and NonBlank CF
            FarPoint.Win.Spread.BlankConditionalFormattingRule blank = new FarPoint.Win.Spread.BlankConditionalFormattingRule(true);
            blank.IsBlank = true;
            blank.BackColor = Color.LimeGreen;
            fpSpread1.ActiveSheet.SetConditionalFormatting(0, 1, blank);
//or
//Blank and NonBlank CF
//FarPoint.Win.Spread.BlankConditionalFormattingRule blank = new FarPoint.Win.Spread.BlankConditionalFormattingRule(true);
//blank.IsBlank = false;
//blank.FontStyle = new FarPoint.Win.Spread.SpreadFontStyle(RegularBoldItalicFontStyle.Bold);
//blank.BackColor = Color.LimeGreen;
//fpSpread1.ActiveSheet.SetConditionalFormatting(0, 0, 3, 3, blank);
        }

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.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

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'Blank and NonBlank CF
        Dim blank As New FarPoint.Win.Spread.BlankConditionalFormattingRule(True)
        blank.IsBlank = True
        blank.BackColor = Color.LimeGreen
        FpSpread1.ActiveSheet.SetConditionalFormatting(0, 1, blank)
'or
'Blank and NonBlank CF
'Dim blank As New FarPoint.Win.Spread.BlankConditionalFormattingRule(True)
'blank.IsBlank = False
'blank.FontStyle = New FarPoint.Win.Spread.SpreadFontStyle(RegularBoldItalicFontStyle.Bold)
'blank.BackColor = Color.LimeGreen
'FpSpread1.ActiveSheet.SetConditionalFormatting(0, 0, 3, 3, blank)
    End Sub