Tracking Visible Rows When Scrolling in GridView for UI for WinForms

Updated on Jan 8, 2026

Environment

Product Version	Product	Author
2025.4.1111	RadGridView for WinForms	Dinko Krastev

Description

In this article we will demonstrate how to track which rows in GridView for UI for WinForms become visible or invisible as the user scrolls vertically. For example, when a user scrolls down, we will get the row number that becomes visible at the bottom and the row number that disappears at the top.

Solution

To achieve this, use the Scroll event of the vertical scrollbar and the VisualRows collection of the GridView. This collection contains the rows currently visible in the view. Compare it with a cached collection to determine which rows were added or removed.

Follow these steps:

1. Subscribe to the Scroll event of the GridView's vertical scrollbar.
2. Access the VisualRows collection to retrieve currently visible rows.
3. Compare the current VisualRows collection with a cached version to identify changes.

Here is an example code snippet:

C#

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        // Subscribe to the Scroll event of the vertical scrollbar.
        this.radGridView1.TableElement.VScrollBar.Scroll += VScrollBar_Scroll;
    }

    private int lastFirstVisibleRowIndex = -1;
	private int lastLastVisibleRowIndex = -1;
	private int previousScrollValue = 0; // Tracks the previous scroll position

	private void VScrollBar_Scroll(object sender, ScrollEventArgs e)
	{
		// Get the current scroll value
		int currentScrollValue = this.radGridView1.TableElement.VScrollBar.Value;

		// Determine the scroll direction
		if (currentScrollValue > previousScrollValue)
		{
			Debug.WriteLine("User is scrolling down.");
			// Call GetVisibleRows to handle visible row changes
			ProcessVisibleRows(true);
		}
		else if (currentScrollValue < previousScrollValue)
		{
			Debug.WriteLine("User is scrolling up.");
			// Call GetVisibleRows to handle visible row changes
			ProcessVisibleRows(false);
		}

		// Update the previous scroll value
		previousScrollValue = currentScrollValue;
	}
	BindingList<GridViewRowInfo> visibleRows = new BindingList<GridViewRowInfo>();
	
	public void ProcessVisibleRows(bool scrollDown)
	{
		int firstVisibleRowIndex = this.radGridView1.TableElement.VisualRows.FirstOrDefault(x => x is GridDataRowElement).RowInfo.Index;
		int lastVisibleRowIndex = this.radGridView1.TableElement.VisualRows.LastOrDefault(x => x is GridDataRowElement).RowInfo.Index;

		if (scrollDown)
		{
			// newly visible row in the view
			var newRowInfoIndex = this.radGridView1.Rows[lastVisibleRowIndex];

			// Notify which row has become visible at the top
			Debug.WriteLine($"Row #{visibleRows.First().Index} has become Invisible.");
			Debug.WriteLine($"Row #{lastVisibleRowIndex} has become visible.");
		}
		else
		{
			// newly visible row in the view
			var newRowInfoIndex = this.radGridView1.Rows[firstVisibleRowIndex];
			Debug.WriteLine($"Row #{firstVisibleRowIndex} has become visible.");
			Debug.WriteLine($"Row #{visibleRows.Last().Index} has become Invisible.");
		}
		visibleRows.Clear();
		this.BeginInvoke((() =>
		{
			GetVisibleRows();

		}));
	}
	
	public void GetVisibleRows()
	{

		foreach (GridRowElement rowElement in this.radGridView1.TableElement.VisualRows.Where(x => x is GridDataRowElement))
		{
			visibleRows.Add(rowElement.RowInfo);
		}
		Debug.WriteLine($"-----------Row #{visibleRows.First().Index} First visible.");
		Debug.WriteLine($"-----------Row #{(visibleRows.Last().DataBoundItem as ParentObject).Id} Last visible.");
	}
}