CODEWITHSUNDEEP
c#wpfmvvm
Offer
Offer

Reputation: 630

How to constantly delay the execution of a method

I have a ICollectionVIew named 'CompanyView'.

I also have a Filter for it called 'CompanyFilter'.

And a Textbox bound to a 'SearchCompanyTitle' property.

As I type in a databound textbox, 'CompanyFilter' gets fired with every letter and the 'CompanyView' gets filtered to show relevant results.

That works fine.

Unfortunately the table I'm filtering has about 9 000 rows so there tends to be a notable delay between the moment you press the key on the keyboard and it showing up on screen.

So what I decided to do instead was ensure that the filter was automatically fired when the user had finished typing. Which raises the question of how does the ViewModel know when the user has finished?

What I did is the below;

    // This is the property the Textbox is bound to
    private string _searchCompanyTitle = "";
    public string SearchCompanyTitle
    {
        get { return _searchCompanyTitle; }
        set
        {
            _searchCompanyTitle = value;
            OnPropertyChanged("SearchCompanyTitle");

            // After a character has been typed it will fire the below method
            SearchCompany();

        }
    }

    // This method is fired by the above property everytime a character is typed into the textbox
    // What this method is meant to do is wait 1000 microseconds before it fires the filter
    // However I need the timer to be reset every time a character is typed, 
    // Even if it hasn't reached 1000 yet
    // But it doesn't do that. It continues to count before triggering the filter
    private async void SearchCompany()
    {
        bool wait = true;

        while (wait == true)
        {
            await Task.Delay(1000);

            wait = false;
        }

        CompanyView.Filter = CompanyFilter;
    }

    // And this is the filter
    private bool CompanyFilter(object item)
    {
        company company = item as company;

        return company.title.Contains(SearchCompanyTitle);
    }

So that's my problem. I need the filter to fire only when the timer hits 1000 and not before. At the same time I need the timer to go back to 0 every time the method is fired by the property. Clearly I'm not doing it right. Any ideas?

Upvotes: 2

Views: 79

Answers (2)

Nicolas C
Nicolas C

Reputation: 754

One solution could be to use the System.Threading.Timer class. You can give it a callback to be called when the time set is elapsed. Put the filter method as the callback and reset the timer's time on every key stroke.

You can find an example here.

--EDIT--

I didn't see that you were using WPF, Sinatr answer is the correct one, just use binding delay

Upvotes: 0

Sinatr
Sinatr

Reputation: 21999

Sounds like a perfect candidate for binding Delay:

<TextBox Text="{Binding SearchCompanyTitle, Delay=1000}"/>

Upvotes: 4

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