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Excel Conditional Formatting
using IronXL;
using IronXL.Formatting.Enums;
using IronXL.Styles;

WorkBook workBook = WorkBook.Load("sample.xlsx");
WorkSheet workSheet = workBook.DefaultWorkSheet;

// Create conditional formatting rule
var rule = workSheet.ConditionalFormatting.CreateConditionalFormattingRule(ComparisonOperator.LessThan, "8");
// Set style options
rule.FontFormatting.IsBold = true;
rule.FontFormatting.FontColor = "#123456";
rule.BorderFormatting.RightBorderColor = "#ffffff";
rule.BorderFormatting.RightBorderType = BorderType.Thick;
rule.PatternFormatting.BackgroundColor = "#54bdd9";
rule.PatternFormatting.FillPattern = FillPattern.Diamonds;
// Apply formatting on specified region
workSheet.ConditionalFormatting.AddConditionalFormatting("A3:A8", rule);

// Create conditional formatting rule
var rule1 = workSheet.ConditionalFormatting.CreateConditionalFormattingRule(ComparisonOperator.Between, "7", "10");
// Set style options
rule1.FontFormatting.IsItalic = true;
rule1.FontFormatting.UnderlineType = FontUnderlineType.Single;
// Apply formatting on specified region
workSheet.ConditionalFormatting.AddConditionalFormatting("A3:A9", rule1);

workBook.SaveAs("applyConditionalFormatting.xlsx");
Imports IronXL
Imports IronXL.Formatting.Enums
Imports IronXL.Styles

Dim workBook As WorkBook = WorkBook.Load("sample.xlsx")
Dim workSheet As WorkSheet = workBook.DefaultWorkSheet

' Create conditional formatting rule
Dim rule = workSheet.ConditionalFormatting.CreateConditionalFormattingRule(ComparisonOperator.LessThan, "8")
' Set style options
rule.FontFormatting.IsBold = True
rule.FontFormatting.FontColor = "#123456"
rule.BorderFormatting.RightBorderColor = "#ffffff"
rule.BorderFormatting.RightBorderType = BorderType.Thick
rule.PatternFormatting.BackgroundColor = "#54bdd9"
rule.PatternFormatting.FillPattern = FillPattern.Diamonds
' Apply formatting on specified region
workSheet.ConditionalFormatting.AddConditionalFormatting("A3:A8", rule)

' Create conditional formatting rule
Dim rule1 = workSheet.ConditionalFormatting.CreateConditionalFormattingRule(ComparisonOperator.Between, "7", "10")
' Set style options
rule1.FontFormatting.IsItalic = True
rule1.FontFormatting.UnderlineType = FontUnderlineType.Single
' Apply formatting on specified region
workSheet.ConditionalFormatting.AddConditionalFormatting("A3:A9", rule1)

workBook.SaveAs("applyConditionalFormatting.xlsx")
NuGet Download
PM > Install-Package IronXL.Excel
Excel Conditional Formatting

Excel Conditional Formatting

The IronXL library supports Conditional Formatting of cells and ranges. Conditional Formatting allows changing the style of the cell, such as the background color or the style of text, based on logical/programmatic rules.

Use CreateConditionalFormattingRule(string formula) to create a conditional formatting rule based on a Boolean formula. When the formula result is true, the cell is highlighted. Please note that the formula to evaluate MUST be a Boolean function.

The CreateConditionalFormattingRule method with three parameters can only take ComparisonOperator.Between and ComparisonOperator.NotBetween as the first parameter.

Use conditional formatting to highlight cells and ranges with specified color and format combinations that are dependent on the cell's true/false value determined by set rules. This allows the ability to analyze data, detect issues, and identify patterns and trends.

Learn to Apply Conditional Formatting in C#
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Version: 2026.10

PM > Install-Package IronXL.Excel
nuget.org/packages/IronXL.Excel/
  1. In Solution Explorer, right-click References, Manage NuGet Packages
  2. Select Browse and search "IronXL"
  3. Select the package and install
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  1. Download and unzip IronXL to a location such as ~/Libs within your Solution directory
  2. In Visual Studio Solution Explorer, right click References. Select Browse, "IronXL.dll"

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