DataGridComboBoxColumn giving poor performance

Feb 23, 2009 at 2:15 PM
Hi,

I'm experiencing some poor performance when I have a datagrid that has one or many combobox columns I see a degredation in performance around sorting the columns and scrolling up/down.

My itemsource is a generic.list(of myclass) and can contain anything from 7 to 200 items.

To work around this I created my own DataGridComboBoxFastColumn which is a copy of the existing class but using a textblock for the normal element rather than TextBlockComboBox class. This did the trick and performance is great.

However I do have a number of problems after implementing this new column class and wondered if anyone else had seen this problem and done anything about it. The type of problems I see are:-

When I have 100+ rows and scroll down to the bottom the new row has a value for the new column? Also when I page down the column values become out of sync. Pasting also causes problems with the code snippett below which can't find the new row index it returns -1.

 

                For Each lobjCell As DataGridCellInfo In Me.SelectedCells
                    If TypeOf lobjCell.Item Is DataRowView Then
                        '
                        ' User the Cell.Item to work out the row in the grid, later we use the items(index) to do this.
                        '
                        Dim lobjDataRowView As DataRowView = DirectCast(lobjCell.Item, DataRowView)
                        Dim lintMinRowIndex As Integer = Items.IndexOf(lobjDataRowView)

 

My new class has the minor changes below to the original DataGridComboBoxColumn it inherits from DataGridColumn as well, I defined a new class called TextBlockFast which I create an instance of instead of TextBlockComboBox although I didn't implement the OnDataContextPropertyChanged... could this be one of the reasons I'm seeing the problems above?

        public class TextBlockFast : TextBlock
        {
            static TextBlockFast()
            {
                DefaultStyleKeyProperty.OverrideMetadata(typeof(TextBlockFast), new FrameworkPropertyMetadata(typeof(TextBlockFast)));
                KeyboardNavigation.IsTabStopProperty.OverrideMetadata(typeof(TextBlockFast), new FrameworkPropertyMetadata(false));
                //DataContextProperty.OverrideMetadata(typeof(TextBlockFast), new FrameworkPropertyMetadata(OnDataContextPropertyChanged));
            }
    }

        protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
        {
            TextBlockFast textBox = new TextBlockFast();

 

            ApplyStyle(/* isEditing = */ false, /* defaultToElementStyle = */ false, textBox);
            //ApplyColumnProperties(comboBox);
            ApplyBinding(TextBinding, textBox, TextBlock.TextProperty);

            return textBox;
        }