ConditionalFormatHelper.cs

using DevExpress.Blazor;
using DevExpress.Data.Filtering.Helpers;

namespace ConditionalFormatSelector.Data {
    public class ConditionalFormatHelper {
        public static List<FormatStyleInfo> GetFormatStyles() {
            return new List<FormatStyleInfo> {
                new FormatStyleInfo("Red Background", "cf-background cf-background-red"),
                new FormatStyleInfo("Green Background", "cf-background cf-background-green"),
                new FormatStyleInfo("Yellow Background", "cf-background cf-background-yellow"),
                new FormatStyleInfo("Red Text", "cf-text cf-text-red"),
                new FormatStyleInfo("Green Text", "cf-text cf-text-green")
            };
        }

        public static bool Evaluate(SimpleFormat format, GridCustomizeElementEventArgs args) {
            switch(format.Condition.ConditionType) {
                case ConditionType.Filter:
                    return EvaluateFilterCriteria(format, args);
                case ConditionType.GreaterThanTotalSummary:
                    return EvaluateGreaterThanTotalSummary(format, args);
                case ConditionType.LessThanTotalSummary:
                    return EvaluateLessThanTotalSummary(format, args);
                default:
                    return false;
            }
        }

        public static bool EvaluateFilterCriteria(SimpleFormat format, GridCustomizeElementEventArgs args) {
            if(format.Condition is not FilterConditionInfo filterInfo)
                return false;

            object dataItem = args.Grid.GetDataItem(args.VisibleIndex);
            var evaluator = new ExpressionEvaluator(
                new EvaluatorContextDescriptorDefault(dataItem.GetType()),
                filterInfo.FilterCriteria
            );
            return (bool)evaluator.Evaluate(dataItem);
        }

        private static bool TryGetSummaryValues(SimpleFormat format, GridCustomizeElementEventArgs args, out double rowValue, out double summaryValue) {
            rowValue = 0;
            summaryValue = 0;

            if(format.Condition is not SummaryConditionInfo summaryInfo)
                return false;

            object dataItem = args.Grid.GetDataItem(args.VisibleIndex);
            rowValue = Convert.ToDouble(dataItem?.GetType()?.GetProperty(summaryInfo.FieldName)?.GetValue(dataItem));

            IGridSummaryItem? totalSummaryItem = args.Grid.GetTotalSummaryItems().FirstOrDefault(item => item.Name == summaryInfo.SummaryName);
            if(totalSummaryItem == null)
                return false;

            summaryValue = Convert.ToDouble(args.Grid.GetTotalSummaryValue(totalSummaryItem));
            return true;
        }

        public static bool EvaluateGreaterThanTotalSummary(SimpleFormat format, GridCustomizeElementEventArgs args) =>
          TryGetSummaryValues(format, args, out double rowValue, out double summaryValue) && rowValue > summaryValue;

        public static bool EvaluateLessThanTotalSummary(SimpleFormat format, GridCustomizeElementEventArgs args) =>
          TryGetSummaryValues(format, args, out double rowValue, out double summaryValue) && rowValue < summaryValue;
    }
}