How to avoid Null Values using Mvvm in Uwp Projecct?

Question

Model: Coffee.cs

 

public class Coffee:BindableBase

{

private int coffeeId;

private string coffeeName;

public int CoffeeId

{

get

{

return coffeeId;

}

set

{

coffeeId = value;

RaisePropertyChanged("CoffeeId");

}

}

public string CoffeeName

{

get

{

return coffeeName;

}

set

{

coffeeName = value;

RaisePropertyChanged("CoffeeName");

}

}

}

 

 

View: CoffeeAdd.xaml

 

<StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">

<StackPanel Orientation="Horizontal">

<TextBlock Text="Coffee Id"/>

<TextBox Width="120" Height="30" Margin="50 0 0 0" Text="{Binding CoffeeId}"/>

</StackPanel>

<StackPanel Orientation="Horizontal" Margin="0 20 0 0">

<TextBlock Text="Coffee Name"/>

<TextBox Width="120" Height="30" Margin="20 0 0 0" Text="{Binding CoffeeName}"/>

</StackPanel>

<StackPanel Orientation="Horizontal" Margin="0 20 0 0">

<Button Content="Add" Width="120" Height="30" Command="{Binding AddCommand}"/>

<Button Content="View" Width="120" Height="30" Margin="20 0 0 0"/>

</StackPanel>

</StackPanel>

 

View Model:CoffeeAddViewModel

 

public class CoffeeAddViewModel:BindableBase

{

private ICoffeeDataService coffeedataservice;

public CoffeeAddViewModel(ICoffeeDataService dataservice)

{

coffeedataservice = dataservice;

LoadCommand();

}

private int _coffeeId;

private string _coffeeName;

public int CoffeeId

{

get

{

return _coffeeId;

}

set

{

_coffeeId = value;

RaisePropertyChanged("CoffeeId");

}

}

public string CoffeeName

{

get

{

return _coffeeName;

}

set

{

_coffeeName = value;

RaisePropertyChanged("CoffeeName");

}

}

public ICommand AddCommand { get; set; }

private void LoadCommand()

{

AddCommand = new CustomCommand(add, canadd);

}

private async void add(object obj)

{

coffeedataservice.AddCoffee(new Model.Coffee { CoffeeId = _coffeeId, CoffeeName = _coffeeName });

var dialog = new MessageDialog("Successfully Added");

await dialog.ShowAsync();

}

private bool canadd(object obj)

{

return true;

}

}

 

 I want to add new coffee details,when i add using Addcommand (custom command) but when add new details is null, so how i avoid this issue?