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I use CustomAggregate  for customization group header text. Until DataGrid component version is everything OK but in higher versions (including actual beta) I´ve got this error:

CS0738 PageAlarms.CustomAggregate does not implement an ISummaryAggregate.CalculateAggregateFunc(). PageAlarms.CustomAggregate.CalculateAggregateFunc() cannot implement the ISummaryAggregate.CalculateAggregateFunc(), member because it does not have the corresponding return type  Action<IEnumerable, string, PropertyDescriptor>.

//My code:

        public class CustomAggregate : ISummaryAggregate 
            public CustomAggregate()
            public string Date { get; set; }
            public Action<System.Collections.IEnumerable, string, PropertyInfo> CalculateAggregateFunc()
                return (items, property, pd) =>
                    var enumerableItems = items as IEnumerable<PageAlarmsModel>;
                    if (pd.Name == "Date")
                        var value = (enumerableItems.First() as PageAlarmsModel).Date;
                        var count = enumerableItems.Count().ToString();
                        this.Date = value.Day + "." + value.Month + "." + value.Year + " - " + "Count: " + count;


    public interface ISummaryAggregate
        // Summary:
        //     Calculates the custom aggregate func for the specified summary column.
        // Return:
        //     The custom aggregate func for the specified summary column.
        Action<IEnumerable, string, PropertyDescriptor> CalculateAggregateFunc();

1 Reply

BS Balasubramani Sundaram Syncfusion Team September 25, 2019 08:37 AM

Hi Tomas,  
Thank you for contacting Syncfusion support.   
It’s already a known issue because we had changed the “Propertyinfo” to "PropertyDescriptor" in summary aggregated due to the reason of upgrading the source to .Net Standard and we have already mentioned about this breaking change in our release note and well we have to change the UG code snippet.  
Please refer the below sample, UG and code snippet, 
Code snippet [C#] 
public class CustomeAggreate : ISummaryAggregate 
    public Action<IEnumerable, string, PropertyDescriptor> CalculateAggregateFunc() 
We hope this helps. Please let us know, if you need any further assistance. 
Balasubramani Sundaram.

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