Login Screen Error - Xamarin Forms Visual Studio 2017 Android

I'm having difficulty fetching the contents of the Entry Element and comparing it with the value being stored in the SQLite DB.

Here is the code for my class Usuarios :

public class Usuarios
{
    [PrimaryKey, AutoIncrement]
    public long? usu_id { get; set; }
    [MaxLength(20)]
    public string usu_nome { get; set; }
    [MaxLength(20)]
    public string usu_senha { get; set; }
}

Code of ContentPage TelaLogin.xaml :

<StackLayout Margin="10">
    <!--Aqui estamos inserindo o logotipo da empresa-->
    <Frame HorizontalOptions="CenterAndExpand" 
           Padding="3" Margin="3">
        <Image Source="logo.jpg" />
    </Frame>
    <Label Text="Login" 
           HorizontalTextAlignment="Center" 
           FontSize="Large" TextColor="Cyan" Style="bold"/>
    <!--Aqui estamos buscando na tabela Usuarios, o Nome e a Senha-->
    <Entry x:Name="txtUsuario" 
           Placeholder="Usuário" 
           PlaceholderColor="Cyan" 
           Text="{Binding Usuario}" 
           TextColor="Cyan" 
           Style="bold"/>
    <Entry x:Name="txtSenha" 
           Placeholder="Senha" 
           PlaceholderColor="Cyan" 
           IsPassword="True" 
           Text="{Binding Senha}" 
           TextColor="Cyan" 
           Style="bold"/>
    <Button Text="Login" 
            Clicked="btnTelaLogin" />
    <Button Text="Tela Usuários" 
            Clicked="btnTelaUsuarios" 
            BackgroundColor="Orange" TextColor="White" />
</StackLayout>

DisplayLogin.xaml.cs:

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class TelaLogin : ContentPage
{
    public TelaLogin ()
    {
        InitializeComponent ();
        //remove a barra de navegação
        NavigationPage.SetHasNavigationBar(this, false);
    }

    private async void btnTelaLogin(object sender, EventArgs e)
    {
        Usuarios login = new Usuarios();
        if (login.usu_nome != null && login.usu_nome != null)
        {                
            if(login.usu_nome ==  txtUsuario.Text && login.usu_senha == txtSenha.Text)
            {
                await Navigation.PushAsync(new TelaPrincipal());
            }
            else
            {
                await DisplayAlert("Erro", "Usuário ou Senha Estão Inválidos. Verifique !!!!", "OK");
            }
        }
        else
        {
            await DisplayAlert("Erro", "Usuário ou Senha Estão Vazios. Verifique as Caixas de texto !!!!", "OK");
        }            
    }

    private async void btnTelaUsuarios(object sender, EventArgs e)
    {
        await Navigation.PushAsync(new TelaUsuarios());
    }
}

I'm not able to test in the following line:

if(login.usu_nome ==  txtUsuario.Text && login.usu_senha == txtSenha.Text)

You are not recognizing txtusuario.Text and txtSenha.Text .

User registration is working.

Where can I be wrong?

Thank you for a response, if possible.