Filter itemsource | 易学教程

问题

With this code I'm setting my Itemsource of my datagrid. However I got more wpf controls that are needed to filter the datagrid even more, for example from a time range. I could write a new query for this but that seems unnecessary as the data is already available, I just need to filter it. But whats the best way to do this?

Any help I could get really appreciate!

DateTime dateStart = CalenderSearch.SelectedDates.First();
DateTime dateEnd = CalenderSearch.SelectedDates.Last();

ObjectQuery<Fouten> fouten = eventsEntities.Foutens;

                var query =
                (from fout in fouten
                 where dateStart <= fout.Datum && dateEnd >= fout.Datum && fout.Rapporten.Treinen.NameTrein == trein.NameTrein
                 orderby fout.Datum, fout.Time


                 select new
                 {
                     Datum = fout.Datum,
                     Time = fout.Time,
                     FoutCode = fout.FoutCode,
                     Omschrijving = fout.Omschrijving,
                     Teller = fout.Teller,
                     Module = fout.Module,
                     FoutId = fout.FoutId

                 }).AsEnumerable().Select(x => new Fouten
                 {
                     Datum = x.Datum,
                     Time = x.Time,
                     FoutCode = x.FoutCode,
                     Omschrijving = x.Omschrijving,
                     Teller = x.Teller,
                     Module = x.Module,
                     FoutId = x.FoutId
                 }).ToList();

if (query.Count == 0)
                    foutensDataGrid.ItemsSource = null;
                else
                    foutensDataGrid.ItemsSource = query;

回答1:

In WPF, each collection that are used as an ItemsSource in a GUI element have an ICollectionView associated with it.
ICollectionView has a Filter property, which is of type Predicate<object>.

If you set this Filter and call Refresh() afterwards, the DataGrid will update itself to only show the items where Filter returned true.

An example how you could use this:

var collectionView = CollectionViewSource.GetDefaultView(foutensDataGrid.ItemsSource);
collectionView.Filter = o => {
    var fouten = o as Fouten;
    //do your filtering, e.g.
    return fouten.Datum <= dateEnd && fouten.Datum >= dateStart;
}
collectionView.Refresh();

回答2:

You can save loaded data in class field and then filter it via handle buttonClicks:

public class YourView
{
    private List<Fouten> loadedData;
    public void LoadData(...)
    {
        ObjectQuery<Fouten> fouten = eventsEntities.Foutens;

        // here you save unfiltered data to the field and then you can use it to filter collection
        loadedData = ...;

        // if you want to filter values immediately you can call filter method right here
        // FilterByFoutCode(someValue);

        if (loadedData.Count == 0)
            foutensDataGrid.ItemsSource = null;
        else
            foutensDataGrid.ItemsSource = loadedData;
    }

    private void FilterByFoutCodeButtonClick(object sender, EventArgs e)
    {
        var filter = FoutCodeTextBox.Content.ToString();
        if(!string.IsNullOrEmpty(filter))
        {
            // if your filter is not empty then filter loadedData by criteria 
            FilterByFoutCode(filter);
        }
    }

    private void FilterByFoutCode(string filter)
    {
        foutensDataGrid.ItemsSource = loadedData.Where(x => x.FoutCode == filter);
    }
}

Also, in the performance context you should not have extra iteration of your collection via select new {...} , .AsEnumerable() and Select(...), just call ToList() immediately after LINQ query.

Finally MVVM pattern is a standard de-facto for WPF it can be useful for your app.

来源：https://stackoverflow.com/questions/35765918/filter-itemsource

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sql

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linq

itemsource