/// <summary>
/// Begins inserting child row before specified child row.
/// </summary>
/// <param name="child">The specified child row, <see langword="null"/> if insert as first child row.</param>
public void BeginInsertBefore(RowPresenter child = null)
{
VerifyInsert(child);
var elementManager = ElementManager;
elementManager?.SuspendInvalidateView();
RowManager.BeginInsertBefore(this, child);
elementManager?.ResumeInvalidateView();
}