I'm getting an error when trying to access the BufferedRenderer.

Ext.Net.GridPanel mainTable = new Ext.Net.GridPanel()
{
	ID = "MainTable",
	Title = mainTableTitle,
	ForceFit = true,
	MultiSelect = true,
	Plugins = {
		new Ext.Net.BufferedRenderer(){
			ID = "MainTable_BufferedRenderer"
		}
	},
	Store = { GetStore() },
	SelectionModel = {
		new Ext.Net.CellSelectionModel(){ }
	}
};
grid.getPlugin('MainTable_BufferedRenderer').scrollTo(0, false);
grid.getStore().reload({ params: { json: jsonString} });
Uncaught TypeError: Cannot call method 'scrollTo' of undefined
Also not sure how to specify the store reload as a callback function?