How to make an event work with Xamarin.Forms and c#

Question

When I declare an event on my Mainpage.xaml, I cannot do the implantation. In the visual says that the implantation was made successfully, but in my cell is all white and can not even navigate it, even music if I hear I can not stop or advance. If I remove the event statement, it works. My Mainpage.xaml:

<?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:local="clr-namespace:Teste1"
             x:Class="Teste1.MainPage">

    <StackLayout Orientation="Vertical">
        <StackLayout Padding="5,5,0,0">
            <Label Text="Adicionar um Produto" TextColor="Green" />
        </StackLayout>
        <StackLayout Padding="10,0,10,0">
            <Entry x:Name="txtNome" Placeholder="Nome do produto" HorizontalOptions="Start" 
                    VerticalOptions="StartAndExpand" HeightRequest="40" WidthRequest="300" FontSize="Small"/>
            <Entry x:Name="txtCategoria" Placeholder="Categoria do produto" HorizontalOptions="Start" 
                    VerticalOptions="StartAndExpand" HeightRequest="40" WidthRequest="300" FontSize="Small" />
            <Entry x:Name="txtPreco" Placeholder="Preço do produto" HorizontalOptions="Start" VerticalOptions="StartAndExpand" 
                    HeightRequest="40" WidthRequest="300" FontSize="Small" />
            <Button HorizontalOptions="FillAndExpand" VerticalOptions="StartAndExpand" HeightRequest="40" Text="Adicionar/Atualizar Produto" 
                    Clicked="btnAdicionar_Clicked" FontSize="Small"/>
        </StackLayout>

        <StackLayout Orientation="Vertical" Padding="10,5,10,0">
            <ListView x:Name="listaProdutos" BackgroundColor="Aqua" SeparatorColor="Blue">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <ViewCell.ContextActions>
                                <MenuItem Clicked="OnAtualizar" CommandParameter="{Binding .}" Text="Atualizar" />
                                <MenuItem Clicked="OnDeletar" CommandParameter="{Binding .}" Text="Deletar" IsDestructive="True" />
                            </ViewCell.ContextActions>
                            <StackLayout Padding="10,10" Orientation="Horizontal">
                                <Label Text="{Binding Nome}" HorizontalOptions="StartAndExpand"/>
                                <Label Text="{Binding Categoria}" TextColor="Blue" HorizontalOptions="Center"/>
                                <Label Text="{Binding Preco}" HorizontalOptions="End"/>
                            </StackLayout>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
        </StackLayout>
    </StackLayout>

</ContentPage>

And my Mainpage.xaml.Cs with the event:

public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();            
        }

        private async void btnAdicionar_OnClicked(object sender, EventArgs e)
        {
            await Navigation.PushModalAsync(new MainPageModal());
        }
    }

What happens is the following: Sometimes when I start the project without the event statement, my smartphone screen turns all white, turn off the application by VS and open by the cell directly and it works. When however, I leave the event enabled, the screen turns white. I turn off the application by VS and when I go by Cel direct, gives this message: Test1.Android stopped. I don’t even know what can be.

Answer 1

His method is called btnAdicionar_OnClicked while the call of the event Clicked button is pointing to btnAdicionar_Clicked

Make the correction that your content will appear on the device/emulator