Pt = winrt::box_value(value) // box up a new value You’ll have to box up a new value and then ask everybody to switch over to it. Once a value is boxed, you can’t change it.
If you look at IReference (which is the interface at the ABI layer that is used for Windows Runtime boxed values), you’ll see that there is a read-only Value property, but no method for setting a new value. In the case of C++/WinRT, I think the error is unlikely to occur because you’re clearly modifying the result of a function call.īut for C# and C++/CX, the property syntax looks a lot like a member variable access, and you may not realize that the property value is secretly the result of a function call.īoxed values are read-only. Error: lvalue required as left operand of assignment Error: expression must be a modifiable lvalue Error: Cannot modify the return value of Point?.Value Most of the time, it’s pretty obvious that you can’t do it: // C# When you box a value in the Windows Runtime, it’s boxed for good.
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