vb.net - Visual Basic Listbox ItemsOfType -

vb.net - Visual Basic Listbox ItemsOfType -

i need find max, average , range of list of numbers entered in listbox. numbers beingness entered using textbox area. trying utilize max value of listbox it's not working. thought why?

dim listgradehighest double = listgrade.items.oftype(of integer).max reshighest.text = listgradehighest

it says: "invalid operation exception unhandled".

try setting listgrade.items.oftype(of integer) listgrade.items.oftype(of double), though i'm not familiar "oftype" might not trying set integer variable declared double

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