How to the prvent the User from entering a value that is not a positive integer in the WPF TextBox using MVVM?

See more:

C#

WPF

C#4.0

MVVM

I want to display a message whenever an user enters a value that is not a positive integer in the TextBox. My current TextBox is bound to an Integer Type. The TxtBox Bordder turns red whenever the User enters a Non -Integer value. But it does not change if a negative value is enetered. I would appreciate some help so as to how to display a message the moment the user enters a value that not a positive integer.

Here is my code


View:

<TextBox Text="{Binding NumberofDays,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}" Height="23" HorizontalAlignment="Left" Margin="251,30,0,0" Name="textBox1" VerticalAlignment="Top" Width="31" />

ViewModel:

private int numberofDays = 0;

public int NumberofDays
        {
            get
            {
                return this.numberofDays ;
            }
            set
            {
                this.numberofDays = value;
                base.OnPropertyChanged("NumberofDays");
            }
        }