VSTO Ctype using for non-object-returning types

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VB

VSTO

VS2015

hi guys

i am new to vsto and trying to convert my existing vba code to vsto code. there is something confusing me. Why should we use Ctype to convert a range object to Excel.Range even if range itself returns a range type rather than object type.

the code ise below. if i dont use Ctype, it gives error(option strcit doesnt allow late binding)

app here represents Excel.Application

CType(app.Columns("A:A"), Excel.Range)

Note:option strict is on, and i deliberately left it on. and i cast all the object-type-returning objects to the relevant type, like Excel.Range, Excel.WorkSheet etc. but i thought i was not supposed to cast range itself or columns to Excel.Range. why am i forced to do this?