My own AggregateFunction

[Andy]

Hello!

I have a table with time of call in seconds.
I grouping my table and add a SumFunction.
All works great!

But I need display result of SumFunction like this: HH:MM:SS where HH - hours, MM - minutes and SS - seconds.

Can you tell me how to do it?

I can create inheritance class from SumFunction like this:

public class mF : Telerik.Windows.Data.SumFunction
    {
        public mF()
        {
        }

        public mF(string propertyName, string calculationField, string caption)
        {
            base.Name = propertyName;
            base.SourceField = calculationField;
            base.Caption = caption;
        }

        private String GetTime(Decimal totalSeconds)
        {
            Int32 hours = (Int32)Math.Floor((double)totalSeconds / (double)3600);
            Int32 minutes = (Int32)Math.Floor((double)(totalSeconds - (hours * 3600)) / (double)60);
            Int32 seconds = (Int32)totalSeconds - (hours * 3600) - (minutes * 60);

            return hours.ToString() + ":" + minutes.ToString() + ":" + seconds.ToString();
        }

        public override Telerik.Windows.Data.AggregateResult Calculate(Telerik.Windows.Data.GroupRecord targetGroup)
        {
            Telerik.Windows.Data.AggregateResult result = base.Calculate(targetGroup);
            result.Value = GetTime(Convert.ToDecimal(result.Value, System.Globalization.CultureInfo.CurrentCulture));
            return result;
        }
    }

But this class properly work only if I have 1 grouping. 
If I add another one grouping i have exception (what it was necessary to expect, because format HH:MM:SS SumFunction cant convert to Decimal).

Please, help.

[Hristo Deshev]

Hi Andy,

Aggregate functions require that you return the same data type at all stages of aggregate calculations. That is why when grouping with more than one level, the second-level grouping crashes -- it gets fed the strings returned by the first-level calculations instead of decimals.

I have a better idea on doing custom formatting for aggregate results -- retemplate the GridViewAggregateResultCell control and use a value converter to convert the total seconds into a HH:MM:SS string. Here is the style I used:

<Style TargetType="telerik:GridViewAggregateResultCell">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="telerik:GridViewAggregateResultCell">
                <ControlTemplate.Resources>
                    <CustomAggregateFunction:SecondsConverter x:Key="secondsConverter" />
                </ControlTemplate.Resources>
                <Border MaxWidth="200" Height="Auto" BorderThickness="1,1,1,1">
                    <Border MinWidth="100" Height="Auto" Background="#00FFFFFF" BorderThickness="1,1,1,1">
                        <StackPanel Orientation="Horizontal">
                            <TextBlock Margin="5,-2,5,0" Foreground="#FF027BA8" Text="{Binding Caption}" />
                            <TextBlock Margin="5,-2,5,0" Foreground="#FF027BA8"
                                       Text="{Binding Value, Converter={StaticResource secondsConverter}}" />
                        </StackPanel>
                    </Border>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

And the SecondsConverter code:

public class SecondsConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        decimal seconds = System.Convert.ToDecimal(value, culture);
        return GetTime(seconds);
    }

    private String GetTime(Decimal totalSeconds)
    {
        Int32 hours = (Int32) Math.Floor((double) totalSeconds / (double) 3600);
        Int32 minutes = (Int32) Math.Floor((double) (totalSeconds - (hours * 3600)) / (double) 60);
        Int32 seconds = (Int32) totalSeconds - (hours * 3600) - (minutes * 60);

        //return hours + ":" + minutes + ":" + seconds;

        //explicitly display single-digit numbers such as 6 minutes as 06 minutes
        return string.Format("{0:00}:{1:00}:{2:00}", hours, minutes, seconds);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new System.NotImplementedException();
    }
}

I am attaching my test project for your reference.

Kind regards,
Hristo Deshev
the Telerik team

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