There is no property on the WebGrid's UltraGridRow object that points to its underlying data object.  Since data objects in ASP.NET need to be recreated during each postback, it's simply not reasonable for WebGrid to try to track this in the same way that WinGrid does.

Instead, you should include some unique identifier in your WebGrid row object.  You can then refer to this value and search your data source for the item that has this unique key.

You can set the DataKeyField of your band to the name of the column that represents this unique value, if you want.  If this represents data from the database, you'd want to use the primary key column for your table.  If you don't want to render this information to the client, you can set the WebGrid column's ServerOnly property to true; if you want it on the client but don't want it shown to the user, then instead set its Hidden property to true.