With virtual mode, you can implement your own data management operations.
This is necessary to maintain the values of unbound columns in bound mode when
the control is sorted by bound columns. The primary use of virtual mode,
however, is to optimize the performance when interacting with large amounts of
You attach the RadGridView control to a cache that you manage, and your code
controls when data rows are pushed and pulled. To keep the memory footprint
small, the cache should be similar in size to the number of rows currently
displayed. When the user scrolls new rows into view, your code requests new
data from the cache and optionally flushes old data from memory.
The following data operations are not supported in Virtual Mode:
When you are implementing virtual mode, you will need to track when a new
row is needed in the data model and when to rollback the adding of the new row.
The exact implementation of this functionality will depend on the
implementation of the data model and the transaction semantics of the data
model; whether commit scope is at the cell or row level.
Implementing the Virtual Mode
With virtual mode, you can manage the interaction between the RadGridView
control and a custom data cache. To implement the virtual mode:
Set the VirtualMode property to true
Handle one or more of the events described further in this topic. You will typically handle at least the CellValueNeeded event,
which enables the control look up values in the data cache.
You will also need to set the RowCount and
ColumnCount (or add columns in your code) properties so
that the grid will know how many rows/columns it needs to display.
The following code snippet demonstrates how to implement the virtual mode
with MockIntegerDataSource (the implementation of this data source can be found in our examples application under the GridView >> Performance >> High Refresh example:
|[C#] Implementing the Virtual Mode ||Copy|
this.radGridView1.EnableSorting = false;
this.radGridView1.EnableFiltering = false;
this.radGridView1.EnableGrouping = false;
this.Load += new EventHandler(Form1_Load);
int COUNT = 100;
void Form1_Load(object sender, EventArgs e)
dataSource = new MockIntegerDataSource(COUNT, COUNT);
this.radGridView1.CellValueNeeded += new GridViewCellValueEventHandler(radGridView1_CellValueNeeded);
this.radGridView1.CellValuePushed += new GridViewCellValueEventHandler(radGridView1_CellValuePushed);
radGridView1.VirtualMode = true;
radGridView1.ColumnCount = dataSource.Columns;
this.radGridView1.RowCount = dataSource.Rows;
void radGridView1_CellValuePushed(object sender, GridViewCellValueEventArgs e)
void radGridView1_CellValueNeeded(object sender, GridViewCellValueEventArgs e)
e.Value = this.dataSource.Source[e.RowIndex].Data[e.ColumnIndex];
|[VB.NET] Implementing the Virtual Mode ||Copy|
Public Sub New()
Me.RadGridView1.EnableSorting = False
Me.RadGridView1.EnableFiltering = False
Me.RadGridView1.EnableGrouping = False
Dim COUNT As Integer = 100
Dim dataSource As MockIntegerDataSource
Protected Overloads Overrides Sub OnLoad(ByVal e As EventArgs)
Me.dataSource = New MockIntegerDataSource(COUNT, COUNT)
AddHandler Me.RadGridView1.CellValueNeeded, AddressOf radGridView1_CellValueNeeded
AddHandler Me.RadGridView1.CellValuePushed, AddressOf radGridView1_CellValuePushed
RadGridView1.VirtualMode = True
RadGridView1.ColumnCount = Me.dataSource.Columns
Me.RadGridView1.RowCount = Me.dataSource.Rows
Sub radGridView1_CellValuePushed(ByVal sender As Object, ByVal e As GridViewCellValueEventArgs)
Sub radGridView1_CellValueNeeded(ByVal sender As Object, ByVal e As GridViewCellValueEventArgs)
e.Value = Me.dataSource.Source(e.RowIndex).Data(e.ColumnIndex)
If your data is read-only, the CellValueNeeded event is the only
event you will need to handle in order to have a working grid control.
Additional virtual-mode events let you enable specific functionality like user
edits, row addition and deletion, and row-level transactions.
Some standard RadGridView events (such as events that occur
when users add or delete rows, or when cell values are edited, parsed,
validated, or formatted) are useful in virtual mode, as well. You can also
handle events that let you maintain values not typically stored in a bound data
source, such as cell ToolTip text, cell and row error text, cell and row
shortcut menu data, and row height data.
The following events are specific only to the grid virtual mode (i.e. when
the VirtualMode property is set to true):
Used by the control to retrieve a cell value
from the data cache for display. This event occurs only for
cells in unbound columns.
the CellValueNeeded event
you should have in mind that the
ColumnIndex parameter depends
on the current order of the columns as set by
the user – reordering columns would change the
Used by the control to commit user input for a cell to the
data cache. This event occurs only for cells in unbound
Call the UpdateCellValue
method when changing a cached value outside of a
CellValuePushed event handler to ensure that the current
value is displayed in the control and to apply any automatic
sizing modes currently in effect.