How to Sum time by values from expression or ReportItem in RDLC reports

Question

Hello,

I want to sum time values o RDLC report, based on values from textbox generated by Expression and I get this error message :
The Value expression for the text box ‘Textbox24’ refers to the report item ‘Textbox23’. Report item expressions can only refer to other report items within the same grouping scope or a containing grouping scope. Letters in the names of report items must use the correct case.

             Time1      Time 2            TotalTime(Expression)// Textbox23  
             1:00           1:00                2:00  
             2:00           2:00                4:00  

Total Time 3:00 3:00 Error Textbox24

How to sum Total time?

Best regards,

Answer 1

Here is an example of summing datetime, you could refer to it.
Xaml:

 <Window.DataContext>  
        <local:ViewModel/>  
    </Window.DataContext>  
    <Grid>  
        <DataGrid ItemsSource="{Binding TestData}" AutoGenerateColumns="False">  
            <DataGrid.Columns>  
                <DataGridTextColumn Header="Time1" Binding="{Binding Time1,StringFormat='HH:mm'}"/>  
                <DataGridTextColumn Header="Time2" Binding="{Binding Time2,StringFormat='HH:mm'}"/>  
                <DataGridTextColumn Header="TotalTime" Binding="{Binding Time3,StringFormat='HH:mm'}"/>  
            </DataGrid.Columns>  
              
        </DataGrid>  
    </Grid>  

Codebehind:

255443-sum-datetime.txt

Update:

<Window x:Class="BindDataFromRDLC.MainWindow"  
        ...  
         xmlns:rdlcreport="clr-namespace:Microsoft.Reporting.WinForms;assembly=Microsoft.ReportViewer.WinForms"   
        mc:Ignorable="d"  
       >  
    <StackPanel>  
         
        <DataGrid ItemsSource="{Binding TestData}" AutoGenerateColumns="False">  
            <DataGrid.Columns>  
                <DataGridTextColumn Header="Time1" Binding="{Binding Time1,StringFormat='HH:mm'}"/>  
                <DataGridTextColumn Header="Time2" Binding="{Binding Time2,StringFormat='HH:mm'}"/>  
                <DataGridTextColumn Header="TotalTime" Binding="{Binding Time3,StringFormat='HH:mm'}"/>  
            </DataGrid.Columns>  
        </DataGrid>  
        <WindowsFormsHost Name="windowsFormsHost1" Height="400" >  
            <rdlcreport:ReportViewer x:Name="_reportviewer" />  
        </WindowsFormsHost>  
    </StackPanel>  
</Window>  

The codebehind:

257040-rdlc.txt

The result:

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Answer 2

=Sum(Fields!TotalTime.Value)