in xamarin project System.InvalidCastException: 'Specified cast is not valid.'

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>

in LandingPage.xaml.g.cs after private void InitializeComponent() { global::Xamarin.Forms.Xaml.Extensions.LoadFromXaml(this, typeof(LandingPage)); } — sunny
I am guessing BackgroundColor="{StaticResource spacegradiant}" should be Background="{StaticResource spacegradiant}" since spacegradiant seems to be a Gradient not a color — Cfun
Yes , your code looks no problem except BackgroundColor="{StaticResource spacegradiant}", you have to ensure spacegradiant is a Color type . — ColeX - MSFT

sunny sunny · Accepted Answer · 2021-04-03T08:00:15

Thanks @Cfun and @ColeX - MSFT

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

in xamarin project System.InvalidCastException: 'Specified cast is not valid.'

1 Answers