windowsforms-16197-controls-and-libraries-spreadsheet-examples-conditional-formatting-how-to-format-unique-or-duplicate-values-blank-cells-and-formula-errors.md
This example demonstrates how to specify the rule that highlights unique or duplicate values, formula errors, etc.
To create a new conditional formatting rule represented by the SpecialConditionalFormatting object, access the collection of conditional formats from the Worksheet.ConditionalFormattings property and call the ConditionalFormattingCollection.AddSpecialConditionalFormatting method. Pass the following parameters:
Specify formatting options to be applied to cells if the condition is true , using the ISupportsFormatting.Formatting property of the SpecialConditionalFormatting object.
To remove the SpecialConditionalFormatting object, use the ConditionalFormattingCollection.Remove, ConditionalFormattingCollection.RemoveAt or ConditionalFormattingCollection.Clear methods.
// Create the rule to identify unique values in cells A2 through A15.
SpecialConditionalFormatting cfRule = worksheet.ConditionalFormattings.AddSpecialConditionalFormatting(worksheet.Range["$A$2:$A$15"], ConditionalFormattingSpecialCondition.ContainUniqueValue);
// Specify formatting options to be applied to cells if the condition is true.
// Set the background color to yellow.
cfRule.Formatting.Fill.BackgroundColor = Color.FromArgb(255, 0xFA, 0xF7, 0xAA);
' Create the rule to identify unique values in cells A2 through A15.
Dim cfRule As SpecialConditionalFormatting = worksheet.ConditionalFormattings.AddSpecialConditionalFormatting(worksheet.Range("$A$2:$A$15"), ConditionalFormattingSpecialCondition.ContainUniqueValue)
' Specify formatting options to be applied to cells if the condition is true.
' Set the background color to yellow.
cfRule.Formatting.Fill.BackgroundColor = Color.FromArgb(255, &HFA, &HF7, &HAA)
The image below shows the result. Unique values in the list of authors are highlighted in yellow.