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My own AggregateFunction

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This is a migrated thread and some comments may be shown as answers.
Andy
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Andy asked on 28 Nov 2008, 03:13 PM
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.

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Hristo Deshev
Telerik team
answered on 01 Dec 2008, 11:41 AM
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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Andy
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Hristo Deshev
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