public class XlCondFmtRuleDuplicates :
    XlCondFmtRuleWithFormatting

Public Class XlCondFmtRuleDuplicates
    Inherits XlCondFmtRuleWithFormatting

// Create an instance of the XlConditionalFormatting class. 
XlConditionalFormatting formatting = new XlConditionalFormatting();
// Specify the cell range to which the conditional formatting rules should be applied (A1:D11).
formatting.Ranges.Add(XlCellRange.FromLTRB(0, 0, 3, 10));
// Create the rule to identify duplicate values in the cell range.
formatting.Rules.Add(new XlCondFmtRuleDuplicates() { Formatting = XlCellFormatting.Bad });
// Create the rule to identify unique values in the cell range.
formatting.Rules.Add(new XlCondFmtRuleUnique() { Formatting = XlCellFormatting.Good });
// Add the specified format options to the worksheet collection of conditional formats.
sheet.ConditionalFormattings.Add(formatting);

' Create an instance of the XlConditionalFormatting class. 
Dim formatting As New XlConditionalFormatting()
' Specify the cell range to which the conditional formatting rules should be applied (A1:D11).
formatting.Ranges.Add(XlCellRange.FromLTRB(0, 0, 3, 10))
' Create the rule to identify duplicate values in the cell range.
formatting.Rules.Add(New XlCondFmtRuleDuplicates() With {.Formatting = XlCellFormatting.Bad})
' Create the rule to identify unique values in the cell range.
formatting.Rules.Add(New XlCondFmtRuleUnique() With {.Formatting = XlCellFormatting.Good})
' Add the specified format options to the worksheet collection of conditional formats.
sheet.ConditionalFormattings.Add(formatting)