MultiSelect + vertical scrolling = big problem

[Andy]

I'm using 2011 Q1 Service Pack 1 release.
When MultiSelect is enabled, the rows unexpectedly get selected if (and it happens easily) the mouse gets out of the scrollbar area and into the grid area while scrolling up/down the grid. This is not a standard Windows behavior and is a huge problem for our customers.

We chose Telerik hoping it helps, but every time we try one of the features, we run into problems... really frustrating.

Below is a sample that shows the problem, and the attached image shows how the rows were incorrectly selected while scrolling. I hope there is a workaround for it.

Andy

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

using Telerik.WinControls.UI;

namespace RadControllTest
{
    public partial class Form5 : Form
    {
        RadGridView myGrid;
        MyGridBehavior myGridBehavior;

        public Form5()
        {
            InitializeComponent();

            SetupGrid();
        }

        private void SetupGrid()
        {
            myGrid = new RadGridView();
            myGrid.Dock = DockStyle.Fill;
            myGrid.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
            myGrid.MultiSelect = true;

            GridViewTextBoxColumn nameColumn = new GridViewTextBoxColumn("Name");
            myGrid.Columns.Add(nameColumn);

            myGrid.ViewCellFormatting += new CellFormattingEventHandler(gridView_ViewCellFormatting);
            myGrid.ChildViewExpanding += new ChildViewExpandingEventHandler(gridView_ChildViewExpanding);
            myGrid.CurrentRowChanging += new CurrentRowChangingEventHandler(myGrid_CurrentRowChanging);

            myGridBehavior = new MyGridBehavior();
            myGrid.GridBehavior = myGridBehavior;

            GridViewTemplate childTemplate = new GridViewTemplate();
            myGrid.Templates.Add(childTemplate);

            GridViewDecimalColumn idColumn = new GridViewDecimalColumn("ID");
            childTemplate.Columns.Add(idColumn);
            GridViewTextBoxColumn childNameColumn = new GridViewTextBoxColumn("Name");
            childTemplate.Columns.Add(childNameColumn);

            GridViewRelation relation = new GridViewRelation(myGrid.MasterTemplate, childTemplate);
            relation.ChildColumnNames.Add("Children");
            myGrid.Relations.Add(relation);

            this.Controls.Add(myGrid);

            BindingList<MockParent> parents = new BindingList<MockParent>();

            for (int i = 0; i < 100; i++)
            {
                MockParent p = new MockParent("Parent " + i.ToString());

                if ((i % 2) == 0)
                {
                    BindingList<MockChild> children = new BindingList<MockChild>();

                    for (int j = 1; j < 5; j++)
                    {
                        children.Add(new MockChild(j, "Child " + j.ToString()));
                    }

                    p.Children = children;
                }

                parents.Add(p);
            }

            myGrid.DataSource = parents;
            myGrid.AutoGenerateHierarchy = true;
            childTemplate.ShowColumnHeaders = false;
            childTemplate.ShowRowHeaderColumn = false;
        }

        void myGrid_CurrentRowChanging(object sender, CurrentRowChangingEventArgs e)
        {
            System.Diagnostics.Debug.WriteLine("CurrentRowChanging");

            if (myGridBehavior.ExpanderClicked)
            {
                System.Diagnostics.Debug.WriteLine("CurrentRowChanging Canceled");
                e.Cancel = true;
            }
        }

        void gridView_ChildViewExpanding(object sender, ChildViewExpandingEventArgs e)
        {
            if ((e.ParentRow != null) && (e.ParentRow.ChildRows.Count < 1))
            {
                e.Cancel = true;
            }
        }

        void gridView_ViewCellFormatting(object sender, CellFormattingEventArgs e)
        {
            GridGroupExpanderCellElement cell = e.CellElement as GridGroupExpanderCellElement;

            if (cell != null && e.CellElement.RowElement is GridDataRowElement)
            {
                if ((cell.RowInfo.ChildRows != null) && (cell.RowInfo.ChildRows.Count > 0))
                {
                    cell.Expander.Visibility = Telerik.WinControls.ElementVisibility.Visible;
                }
                else
                {
                    cell.Expander.Visibility = Telerik.WinControls.ElementVisibility.Hidden;
                }
            }
        }


        private class MyGridBehavior : BaseGridBehavior
        {
            public bool ExpanderClicked { get; set; }

            public override bool OnMouseDown(MouseEventArgs e)
            {
                System.Diagnostics.Debug.WriteLine("MouseDown");

                ExpanderClicked = false;

                if (this.CellAtPoint is GridGroupExpanderCellElement)
                {
                    GridViewRowInfo row = this.CellAtPoint.RowInfo;
                    if ((row != null) && (row.ChildRows.Count > 0))
                    {
                        ExpanderClicked = true;
                    }
                }

                return base.OnMouseDown(e);
            }

            public override bool OnMouseUp(MouseEventArgs e)
            {
                System.Diagnostics.Debug.WriteLine("MouseUp");

                ExpanderClicked = false;

                return base.OnMouseUp(e);
            }
        }


        private class MockParent
        {
            public string Name { get; set; }

            public BindingList<MockChild> Children { get; set; }

            public MockParent(string s)
            {
                Name = s;
            }
        }

        private class MockChild
        {
            public int ID { get; set; }
            public string Name { get; set; }

            public MockChild(int id, string s)
            {
                ID = id;
                Name = s;
            }
        }
    }
}

[Alexander]

Hello Andy,

Thank you for your question.

I confirm this behavior of the RadGridView control. I have added this issue to our PITS. Thank you for reporting it. You Telerik points have been updated.

As a workaround, you can create a custom GridRowBehavior and process the MouseMove logic only if a row has been clicked:

BaseGridBehavior baseGridBehavior = this.radGridView1.GridBehavior as BaseGridBehavior;
baseGridBehavior.UnregisterBehavior(typeof(GridViewDataRowInfo));
baseGridBehavior.RegisterBehavior(typeof(GridViewDataRowInfo), new CustomGridDataRowBehavior());

public class CustomGridDataRowBehavior : GridDataRowBehavior
{
    private GridRowElement rowElement;

    protected override bool OnMouseDownLeft(MouseEventArgs e)
    {
        this.rowElement = this.GetRowAtPoint(this.GridViewElement.ElementTree, e.Location);
        return base.OnMouseDownLeft(e);
    }

    public override bool OnMouseMove(MouseEventArgs e)
    {
        if (this.rowElement == null)
        {
            return false;
        }

        return base.OnMouseMove(e);
    }

    private GridRowElement GetRowAtPoint(ComponentElementTree componentTree, Point point)
    {
        RadElement elementUnderMouse = componentTree.GetElementAtPoint(point);

        while (elementUnderMouse != null)
        {
            GridRowElement item = elementUnderMouse as GridRowElement;

            if (item != null)
            {
                return item;
            }

            elementUnderMouse = elementUnderMouse.Parent;
        }

        return null;
    }
}

I hope it helps.

Best regards,
Alexander
the Telerik team