未知事件DropGesture

如何解决未知事件DropGesture

我尝试为拖放添加事件，但我仍然收到此消息：

Could not resolve type with token 0100004d from typeref (expected class 'Xamarin.Forms.DropGestureRecognizer' in assembly 'Xamarin.Forms.Core,Version=2.0.0.0,Culture=neutral,PublicKeyToken=null')'

我正在使用Nuget软件包。

是否有要添加的扩展名？

这是使用的代码。

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             xmlns:local="clr-namespace:SafeMountain"
             x:Class="SafeMountain.MainPage"
             xmlns:control="clr-namespace:SafeMountain.UserControls"
             NavigationPage.HasNavigationBar="False">
    <Grid x:Name="gridMain">
        <StackLayout Orientation="Vertical" VerticalOptions="FillAndExpand">
            <ScrollView Orientation="Vertical">
                <StackLayout Margin="15,15,0" x:Name="slItems">
                    <StackLayout.GestureRecognizers>
                        <DropGestureRecognizer AllowDrop="True" Drop="DropGestureRecognizer_Drop"/>
                    </StackLayout.GestureRecognizers>
                    <Label x:Name="lblLastPosCatch" HorizontalOptions="Center" HorizontalTextAlignment="Center" TextColor="LightGray" FontSize="Micro"/>
                    <StackLayout x:Name="slDeconnexion">
                        <Label x:Name="lblDeconnexionInfo" TextColor="Red" Text="Déconnecté du réseau cellulaire" HorizontalTextAlignment="Center"/>
                    </StackLayout>
                </StackLayout>
            </ScrollView>
        </StackLayout>
    </Grid>
</ContentPage>