Help with RadTextboxControl Autocomplete

[Randy]

In UI for WinForms, I'm having trouble understanding how to link a RadTextBoxControl to a database containing ~ 60,000 part numbers.  Obviously I don't want to fetch the whole list into RAM, I want to query the db every time the user types a character.  What event do I trigger on to refresh the list, and how do I specify the query itself (search parameters, number of results returned, etc.)?

I've tried binding the .AutoCompleteDataSource to a List<string> and updating that list via the database every time the TextChanged event fires, but it doesn't work - updating the datasource doesn't re-bind to the control, and setting the property again seems to wipe out any autocomplete in progress.

private void radPnTextBox_TextChanged(object sender, EventArgs e)
{
    //populate autocomplete list
    if (VDO != null)
    {
        //fetch updated list from database
        PnDropdownList = VDO.GetAutoCompletePnDescription(radPnTextBox.Text.ToUpper());

        //re-bind the this list by re-assigning the datasource
        radPnTextBox.AutoCompleteDataSource = PnDropdownList;
    }
}

Are there any code examples of using autocomplete function bound to a database?

Thanks,
Randy

[George]

Hello Randy,

Thank you for writing.

RadDropDownList without its arrow button will be perfect for this case. You can create a custom AutoCompleteSuggest helper which will take the items from a remote database instead of filtering existing ones, in my example it will take them from a collection. Please, refer to the code below:

public partial class Form1 : Form
{
    List<string> serverSideItems = new List<string>();

    public Form1()
    {
        InitializeComponent();

        Enumerable.Range(0, 5000).ToList().ForEach(x => serverSideItems.Add("Item " + x));

        RadDropDownList list = new RadDropDownList
        {
            Parent = this,
            Dock = DockStyle.Top,
        };

        list.DropDownListElement.ArrowButton.Visibility = Telerik.WinControls.ElementVisibility.Collapsed;

        list.AutoCompleteMode = AutoCompleteMode.Suggest;
        list.DropDownListElement.AutoCompleteSuggest = newServerAutoCompleteSuggestHelper(list.DropDownListElement, serverSideItems);
    }
}

class ServerAutoCompleteSuggestHelper : AutoCompleteSuggestHelper
{
    private IList<string> serverSideItems;
    private bool endingUpdate;

    public ServerAutoCompleteSuggestHelper(RadDropDownListElement owner, IList<string> serverSideItems)
        :base(owner)
    {
        this.serverSideItems = serverSideItems;
    }

    protected override void SyncOwnerElementWithSelectedIndex()
    {
        if (!endingUpdate)
        {
            base.SyncOwnerElementWithSelectedIndex();
        }
        else
        {
            this.endingUpdate = false;
        }
    }

    public override void ApplyFilterToDropDown(string filter)
    {
        this.DropDownList.ListElement.BeginUpdate();
        this.DropDownList.ListElement.Items.Clear();

        //make sure that this line is synchronous, if it is asynchronous consider using await/async - http://msdn.microsoft.com/en-us/library/hh191443.aspx
        List<string> newItems = serverSideItems.AsParallel().Where(x => x.Contains(filter)).ToList();

        newItems.ForEach(x => this.DropDownList.ListElement.Items.Add(newRadListDataItem(x)));

        this.endingUpdate = true;
        this.DropDownList.ListElement.EndUpdate();
    }
}

Feel free to modify it as you like, since the current implementation is just a mere example.

As a side note, in order to allow RadDropDownList refresh when its data source changes it should be a BindingList, since a simple List does not support notifications.

Let me know, should you have other questions.

Regards,
George
Telerik

 

 

[Randy]

George,
Thanks for your post.  This looks like exactly what I needed.  When I tried to test it, I get an error at "newRadListDataItem" - is that supposed to be defined somewhere?

Also, as I'm on .NET 3.5, I can't use .AsParallel, but perhaps I can find a way around that, or migrate to .NET 4.0.

Thanks again,
Randy

[Randy]

Disregard the question about newRadListDataItem, I see now there should have been a space after the new keyword.  The same with newServerAutoCompleteSuggestHelper.

Also I understand now that the AsParallel is not necessary, it seems it is only a slight speedup for multi-core systems - I had thought initially it was an asynchronous call.  Since I will be fetching just small lists from the database, there should be no need for this optimization.

I would like to have the list behave in the SuggestAppend mode though, and as I'm looking through the API documentation I see an AutoCompleteAppendHelper that is fairly different (no ApplyFilterToDropDown method).  I don't see an AutoCompleteSuggestAppendHelper. Is there any example code for implementing SuggestAppend mode?

Thanks again,
Randy

[George]

Hello Randy,

Thank you for writing.

The AppendHelper is a bit different. Below you can see a sample implementation:

class ServerAutoCompleteAppendHelper : AutoCompleteAppendHelper
{
    private IList<string> serverSideItems;

    public ServerAutoCompleteAppendHelper(RadDropDownListElement owner, IList<string> serverSideItems)
        : base(owner)
    {
        this.serverSideItems = serverSideItems;
    }

    public override void AutoComplete(KeyPressEventArgs e)
    {
        string findString = this.GetFindString(e);

        string result = this.serverSideItems.Where(x => x.StartsWith(findString) && x != findString).OrderBy(x => x.Length).FirstOrDefault();
        if (result != null)
        {
            Owner.EditableElementText = result;
            Owner.SelectionStart = findString.Length;
            Owner.SelectionLength = Owner.EditableElementText.Length;
            e.Handled = true;
        }
    }

    private Func<KeyPressEventArgs, string> getFindString;
    public Func<KeyPressEventArgs, string> GetFindString
    {
        get
        {
            if (this.getFindString == null)
            {
                var method = typeof(AutoCompleteAppendHelper).GetMethod("CreateFindString", BindingFlags.Instance | BindingFlags.NonPublic);
                this.getFindString = (Func<KeyPressEventArgs, string>)Delegate.CreateDelegate(typeof(Func<KeyPressEventArgs, string>), this, method);
            }

            return this.getFindString;
        }
    }
}

I hope this information is helpful.

Regards,
George
Telerik