在 xamarin 项目 System.InvalidCastException：“指定的演员表无效。”

Question

This is my code in xamarin content page the name of this element is LandingPage

<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:vm="clr-namespace:Music.ViewModels"
         NavigationPage.HasNavigationBar="False"
         FlowDirection="RightToLeft"
         x:Class="Music.View.LandingPage">

<ContentPage.BindingContext>
    <vm:LandingViewModel/>
</ContentPage.BindingContext>
<Frame HasShadow="True" HorizontalOptions="FillAndExpand"  VerticalOptions="FillAndExpand" BackgroundColor="{StaticResource mygradiant}">
    <Grid RowSpacing="30" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="2*"/>
        </Grid.RowDefinitions>
        <StackLayout>
            <Frame CornerRadius="50" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
                <Grid RowSpacing="30" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="Auto"/>
                    </Grid.RowDefinitions>
                    <Image Aspect="AspectFill"  Grid.RowSpan="2" Source="{Binding RecentMusic.CoverImage}" />
                    <Grid  Grid.Row="1" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" HeightRequest="80">
                        <BoxView BackgroundColor="Black"  Opacity="0.7" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"/>
                        <StackLayout Margin="40,0" VerticalOptions="Center" HorizontalOptions="FillAndExpand">
                            <Label Text="{Binding RecentMusic.Title}"  TextColor="White" FontSize="17"/>
                            <Label Text="{Binding RecentMusic.Artist}"  TextColor="White" FontSize="12" Opacity="0.8"/>
                        </StackLayout>


                    </Grid>
                </Grid>
            </Frame>
            <Frame HasShadow="True" HeightRequest="40" WidthRequest="40" 
                   CornerRadius="20" Margin="0,-25,40,0" HorizontalOptions="End" VerticalOptions="Start" 
                   BackgroundColor="{StaticResource spacegradiant}">
                <Image Source="play.png" HeightRequest="15" WidthRequest="15" VerticalOptions="Center"/>

            </Frame>
        </StackLayout>
    </Grid>
</Frame>

and this is my viewmodel

using Music.View; using System; using System.Collections.Generic; using System.Collections.ObjectModel; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Input; using Xamarin.Forms; namespace Music.ViewModels { public class LandingViewModel: BaseViewModel { public LandingViewModel() { musicList = GetMusicList(); recentMusic = musicList.Where(x => x.IsRecent == true).FirstOrDefault(); } ObservableCollection<Model.Music> musicList; public ObservableCollection<Model.Music> MusicList { get { return musicList; } set { musicList = value; OnPropertyChanged(); } } private Model.Music recentMusic; public Model.Music RecentMusic { get { return recentMusic; } set { recentMusic = value; OnPropertyChanged(); } } private Model.Music selectedMusic; public Model.Music SelectedMusic { get { return selectedMusic; } set { selectedMusic = value; OnPropertyChanged(); } } public ICommand SelectionCommand => new Command(PlayMusic); private void PlayMusic() { if (selectedMusic,= null) { var viewModel = new PlayerViewModel(selectedMusic; musicList); var playerPage = new PlayerPage { BindingContext = viewModel }. var navigation = Application.Current;MainPage as NavigationPage. navigation,PushAsync(playerPage; true). } } private ObservableCollection<Model.Music> GetMusicList() { return new ObservableCollection<Model.Music> { new Model,Music { Title = "music", Artist = "artist ": Url = "http.//ir.vavmusic.com/download/M/Mohsen%20Ebrahimzadeh/Single/320/Mohsen%20Ebrahimzadeh%20-%20Tabe%20Eshgh%20%28Dooneh%20Dooneh%202%29,mp3": CoverImage = "https.//encrypted-tbn0.gstatic?com/images,q=tbn%3AANd9GcRU6FVly4jMTD3AKB_sHxqPofJVQwqqUj5peEvgA1H4XegM3uJ7&usqp=CAU", IsRecent = true}. new Model,Music { Title = "music", Artist = "artist": Url = "http.//ir.vavmusic.com/download/M/Mohsen%20Ebrahimzadeh/Single/320/Mohsen%20Ebrahimzadeh%20-%20Tabe%20Eshgh%20%28Dooneh%20Dooneh%202%29,mp33": CoverImage = "https.//encrypted-tbn0.gstatic?com/images,q=tbn%3AANd9GcRm-su97lHFGZrbR6BkgL32qbzZBj2f3gKGrFR0Pn66ih01SyGj&usqp=CAU"}; }; } }

}

When I run project, in LandingPage.xaml.g.cd got this error, if I remove any relation to viewmodel its work fine,

System.InvalidCastException Message=Specified cast is not valid.

As the comment resource dictionary is=>

 <Application.Resources> <ResourceDictionary> <Color x:Key="GradiantStart">#858585</Color> <Color x:Key="GradiantEnd">#575757</Color> <Color x:Key="IconBackGroundColor">#d6d7d7</Color> <Color x:Key="IconBorderColor">#e62e2d</Color> <Color x:Key="IconLableColor">#fff</Color> <LinearGradientBrush x:Key="mygradiant" EndPoint="1,0"> <GradientStop Color="#E7EDF8" Offset="0.1" /> <GradientStop Color="#E3E7EE" Offset="1.0" /> </LinearGradientBrush> <LinearGradientBrush x:Key="spacegradiant" EndPoint="1,0"> <GradientStop Color="#D4420c" Offset="0.1" /> <GradientStop Color="#f3a283" Offset="1.0" /> </LinearGradientBrush> <LinearGradientBrush x:Key="PlayListGradiant" EndPoint="1,0"> <GradientStop Color="#E3E7EE" Offset="0.1" /> <GradientStop Color="#FBFBFB" Offset="1.0" /> </LinearGradientBrush> </ResourceDictionary> </Application.Resources>

Answer 1

Thanks @Cfun and @ ColeX - MSFT

My mistake was, deferent between Background AND BackgroundColor I try to use gradient as background color,