https://learn.microsoft.com/ja-jp/dotnet/api/system.web.ui.webcontrols.hierarchicaldataboundcontrol.performdatabinding?view=netframework-4.8.1
HierarchicalDataBoundControl.PerformDataBinding Method (System.Web.UI.WebControls) | Microsoft Learn
When overridden in a derived class, binds data from the data source to the control.
system webmethoduimicrosoftlearn