Change Default Selection Logic

[Shawn]

The data in all of our multi column combo boxes has a key value always as the first column in the grid. We want our users to be able to enter one of those key values then hit tab to select it. However, in some cases, just entering the key value doesn't cause the record with that key value to be at the top, so when the user hits tab it selects the top record instead of the record matching the key value entered.

See example below with US states as values:

 

In scenarios like these, I'd like to be able override the default selection logic and see if there is a record where the text in the search box exactly matches a key value, if so, select that value instead of the first value.

This was the last thing I tried inside the PreviewKeyDown event but it seemed to freeze and then not work as expected.

if (e.Key == System.Windows.Input.Key.Tab)
{
    string typedText = MultiColumnComboBox
        .FindChildByType<TextBox>()
        .Text
        .Trim();

    if (MultiColumnComboBox.DropDownContentManager.DropDownElement is RadGridView gridView)
    {
        string keyFieldName = gridView.Columns[0].UniqueName;

        var itemToSelect = gridView.Items
            .OfType<DataRow>()
            .FirstOrDefault(row =>
            {
                var keyValue = row[keyFieldName];
                return keyValue != null &&
                       keyValue.ToString().Equals(typedText, StringComparison.OrdinalIgnoreCase);
            });

        if (itemToSelect != null)
        {
            gridView.SelectedItem = itemToSelect;
        }
    }
}

[Martin Ivanov]

I've tested your code and it doesn't freeze on my side, but indeed it doesn't work as intended. To fix this should delay the selection a bit.

private void RadMultiColumnComboBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Tab)
    {
        var mccb = (RadMultiColumnComboBox)sender;
        var text = mccb.AutoCompleteProvider.SearchText;

        var dt = (DataTable)mccb.ItemsSourceProvider.ItemsSource;
        var itemToSelect = dt.Rows.OfType<DataRow>()
            .FirstOrDefault(row => row["Id"] != null && row["Id"].ToString().Equals(text, StringComparison.OrdinalIgnoreCase));
        if (itemToSelect != null)
        {
            Dispatcher.BeginInvoke(new Action(() =>
            {
                mccb.SetCurrentValue(RadMultiColumnComboBox.SelectedItemProperty, itemToSelect);
            }));
        }
    }
}

You can see this in the attached project. I hope it helps.