advancedDatagrid multipleSelection: Was a row already selected?

after multiple Selection in a advanced datagrid, I want to check if the clicked row, was already selected. Anyway my idea below (in the nested if clause I want to check if the newly clicked item's processing data is already in the added Array Collection) is not working, but I assume there must be a better way to differiante if an click was made on a already selected row.

Probably I was not as clear in my description as needed, please ask your questions!

Thank you very much, already in advance, Werner

model.processingData = out; 
if    (model.selectedIndices.length > 1){                   
       //check if item already added
       var tempInt:int = model.multipleProcessingData.getItemIndex(model.processingData);
        if (tempInt == -1){
            model.multipleProcessingData.addItem(model.pr开发者_开发知识库ocessingData);
        }

 } else{
       model.multipleProcessingData.removeAll();
       model.multipleProcessingData.addItem(model.processingData);
 }

tssss, there is a contains function for ArrayCollection:

if (!model.selectedDrawings.contains(model.lastSelectedDrawing)){
                        model.selectedDrawings.addItem(model.lastSelectedDrawing);
                    }