Show Child Count in a DataGrid

Show Child Count in a DataGrid

by jbrooks 11. March 2013 17:49

I have an application with the following as part of the data model:

image

So an Account can have many Users and a user can belong to many Accounts. I wanted to show the Accounts in a DataGrid along with the number of Users that were linked to that account like show in the 3rd column here:

image

The way I did this is to use a converter to count the number of entities in each Account.xrefAccountsUser set.  The DataGrid is bound to Accounts and the the XAML for the 3rd column is:

<sdk:DataGridTextColumn  Header="Users" 
Binding="{Binding xrefAccountsUsers, Converter={StaticResource setToCountConverter}}"
 />

The converter is where we count up the number of entities in the related entity set (xrefAccountsUsers in this case.)  I could not find a type that I could cast the value to that had a Count property, so I  ended up casting it to IEnumerable and then loop thru the set and I do a count manually.  There should never be very many accounts so performance isn’t an issue.

public class SetToCountConverter : IValueConverter
{
    public object Convert(object value,
                                Type targetType,
                                object parameter,
                                System.Globalization.CultureInfo culture)
    {
        int cnt = 0;
        IEnumerable set = value as IEnumerable;
 
        if (set == null)
            return "0";
 
        foreach (var item in set)
            cnt++;
 
        return cnt.ToString();
    }
 
    public object ConvertBack(object value,
                                Type targetType,
                                object parameter,
                                System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Tags:

Silverlight | Development | XAML

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