RadControls for WinForms
Contents

Each row has a Tag property associated with it of type object where you can store a custom object.

Copy[C#] Setting the Tag property of a row
this.radGridView1.Rows[1].Tag = "Some tag";
Copy[VB.NET] Setting the Tag property of a row
Me.RadGridView1.Rows(1).Tag = "Some tag"

 

Copy[C#] Setting the Tag property of cells in CellFormatting event
void radGridView1_CellFormatting(object sender, Telerik.WinControls.UI.CellFormattingEventArgs e)
{
    if (e.CellElement.RowIndex % 2 == 0)
    {
        e.CellElement.RowInfo.Tag = "Some tag";
    }
    else
    {
        e.CellElement.RowInfo.Tag = "Hide row";
    }
}
Copy[VB.NET] Setting the Tag property of cells in CellFormatting event
Private Sub RadGridView1_CellFormatting(ByVal sender As Object, ByVal e As Telerik.WinControls.UI.CellFormattingEventArgs) Handles RadGridView1.CellFormatting
    If (e.CellElement.RowIndex Mod 2 = 0) Then
        e.CellElement.RowInfo.Tag = "Some tag"
    Else
        e.CellElement.RowInfo.Tag = "Hide row"
    End If
End Sub

The most natural place to use the tag is in some of the row/cell events. For example, to make the content of certain cells invisible use the following code:

Copy[C#] Collapsing all rows with the specified tag
void radGridView1_CellFormatting1(object sender, Telerik.WinControls.UI.CellFormattingEventArgs e)
{
    if (e.CellElement.RowInfo.Tag is String && (string)e.CellElement.RowInfo.Tag == "Hide row")
    {
        e.CellElement.Visibility = Telerik.WinControls.ElementVisibility.Collapsed;
    }
}
Copy[VB.NET] Collapsing all rows with the specified tag
Private Sub RadGridView1_CellFormatting1(ByVal sender As Object, ByVal e As Telerik.WinControls.UI.CellFormattingEventArgs) Handles RadGridView1.CellFormatting
    If TypeOf e.CellElement.RowInfo.Tag Is [String] AndAlso DirectCast(e.CellElement.RowInfo.Tag, String) = "Hide row" Then
        e.CellElement.Visibility = Telerik.WinControls.ElementVisibility.Collapsed
    End If
End Sub
Note

Note: Cells also have Tag property but it differs substantially from rows one because of the UI Virtualization. Cells are reused and when you scroll the tag value remains unchanged while cell data value is updated.