This is an addition to the base EmailValidator in flex. This in addition to EmailValidator triggers error if an email address is already present in a given data provider.
Note: As of now it only supports ArrayCollection as data provider. You may update the code accordingly for your use.

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Most of the results found on net were disappointing. Since they just provided a solution to place the ComboBox  on datagrid header. The basic step was to override the setter function data in ComboBox class which is intended to be the DataGridHeader Renderer

override public function set data(value:Object):void
{
	if(value is DataGridColumn)
	{
		//Don't do anything
	}
        else
	{
		super.data = value
	}
}

Unfortunately, it didn’t really work well. The values in ComboBox never remained the selected once after it was sorted. After digging in to the main classes I came up with a solution.

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