In SharePoint 2013 when you need to use ASP.NET controls for custom settings in the tool part pane for your Webpart which inherits from System.Web.UI.WebControls.WebParts.WebPart, we would need to create an Editor Part to achieve it.
Note:
If the custom Webpart inherits from Microsoft.SharePoint.WebPartPages.WebPart then a Tool Part needs to be created. This blog shows how a Checkbox List control within Editor Part is used in the tool part pane to do some configuration.
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