OnPlatform doesn't work - No property, bindable property, or event found for 'WidthRequest'...

I can't use OnPlatform almost nowhere, with the same error always.

For example:

"No property, bindable property, or event found for 'WidthRequest', or mismatching type between value and property."

On this simple XAML code:

                    <Image
                        HorizontalOptions="CenterAndExpand"
                        Source="{Binding LockImageSource}"
                        VerticalOptions="Center">
                        <Image.WidthRequest>
                            <OnPlatform x:TypeArguments="x:Double">
                                <On Platform="iOS">30</On>
                                <On Platform="Android">48</On>
                            </OnPlatform>
                        </Image.WidthRequest>
                    </Image>