<TelerikSpreadsheet Height="500px" Width="100%">
    <SpreadsheetSheets>
        <SpreadsheetSheet Name="Sheet1">
            <SpreadsheetSheetColumns>
                <SpreadsheetSheetColumn Index="0" Width="100px"></SpreadsheetSheetColumn>
                <SpreadsheetSheetColumn Index="1" Width="200px"></SpreadsheetSheetColumn>
            </SpreadsheetSheetColumns>
            <SpreadsheetSheetRows>
                <SpreadsheetSheetRow Index="0">
                    <SpreadsheetSheetCell Value="Item"></SpreadsheetSheetCell>
                    <SpreadsheetSheetCell Value="Price"></SpreadsheetSheetCell>
                </SpreadsheetSheetRow>
                <SpreadsheetSheetRow Index="1">
                    <SpreadsheetSheetCell Value="Apples"></SpreadsheetSheetCell>
                    <SpreadsheetSheetCell Value="1.50"></SpreadsheetSheetCell>
                </SpreadsheetSheetRow>
                <SpreadsheetSheetRow Index="2">
                    <SpreadsheetSheetCell Value="Bananas"></SpreadsheetSheetCell>
                    <SpreadsheetSheetCell Value="2.00"></SpreadsheetSheetCell>
                </SpreadsheetSheetRow>
            </SpreadsheetSheetRows>
        </SpreadsheetSheet>
    </SpreadsheetSheets>
</TelerikSpreadsheet>

ListDataValidationRuleContext context = new(worksheet, ri, ci)
{
  InputMessageTitle = "Restricted input",
  InputMessageContent = "The input is restricted to the week days.",
  ErrorStyle = ErrorStyle.Stop,
  ErrorAlertTitle = "Wrong value",
  ErrorAlertContent = "The entered value is not valid. Allowed values are the week days!",
  InCellDropdown = true,
  Argument1 = "Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday"
};

cell.SetDataValidationRule(new ListDataValidationRule(context));