搜索文档时如何在WPF中使用进度条（圆形）？

Question

I want to use progress bar - so users should see that it is on progress while I am searching some documents through full text search. Assume, I have 50 000 documents. I want to find documents which have word "building construction" using Full Text Search. It is working fine for now. But when I search I have to wait 5-15 seconds. I want to use load balance in this period of search. Is it possible? How should I use it? Using multi-threading or something else? How can I understand if 1st thread finished working? Please provide me with some clear ideas and codes.

Answer 1

Assuming you're talking about the wait cursor here, or do you mean a progress bar in your window? For the wait cursor you need this either in your window or on whichever element you want the cursor to appear over

<Window.Style>
    <Style TargetType="{x:Type Window}">
        <Style.Triggers>
            <DataTrigger Binding="{Binding Path=IsBusy}" Value="True">
                <Setter Property="Cursor" Value="Wait" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Window.Style>

This can then be activated by changing the IsBusy property to true either on your ViewModel or in code behind if you're not doing MVVM

To tackle the rest of your post, are you looking for a way to push your sql call to a worker so that it won't lock up the UI?

Assuming that this is what you wanted, here goes

public class SearchViewModel : INotifyPropertyChanged
{
    public bool IsBusy
    {
        get { return _isBusy; }
        set
        {
            _isBusy = value;
            RaisePropertyChanged("IsBusy");
        }
    }

    public void Search(string searchPhrase)
    {
        IsBusy = true;
        Task.Factory
            .StartNew(p =>
            {
                // This is where you do your database thing and return your results
            }, searchPhrase)
            .ContinueWith(t =>
            {
                // And this is where you use the returned results in t.Result
                // don't forget to check for errors :)
                IsBusy = false;
            }, TaskScheduler.FromCurrentSynchronizationContext());
    }
}

or if you prefer the async approach

public class SearchViewModel : INotifyPropertyChanged
{
    public async Task Search(string searchPhrase)
    {
        IsBusy = true;
        var results = await DoDatabaseSearch(searchPhrase);
        // do stuff with results
        IsBusy = false;
    }

    public async Task<IEnumerable<SearchResult>> DoDatabaseSearch(string searchPhrase)
    {
        // This is where you would do your search
    }
}