I am struggling with displaying a validation error message. I have set a validation condition, but still cannot display a validation message. I would like to have a little message above my TextBox when data is not valid.
My c# code is follwing:
public class Child
{
public string Name { get; set; }
public int Age { get; set; }
}
public partial class MainWindow : Window
{
List<Child> children = new List<Child>();
public MainWindow()
{
InitializeComponent();
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
children.Add(new Child { Name = "johny", Age = 22 });
children.Add(new Child { Name = "johnsy", Age = 212 });
children.Add(new Child { Name = "johdny", Age = 222 });
pnlChildren.DataContext = children;
}
}
public class AgeValidation : ValidationRule
{
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
int age;
if (Int32.TryParse(value.ToString(), out age))
{
if (age >= 3)
{
return new ValidationResult(true, null);
}
}
return new ValidationResult
(false, "Name cannot be more than 3 characters long.");
}
}
and XAML:
<Window x:Class="WpfApplication9.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication9"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
<StackPanel Name="pnlChildren">
<ListBox Height="100" Width="120" ItemsSource="{Binding}" IsSynchronizedWithCurrentItem="True">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Path=Name}"/>
<TextBlock Text=" ," />
<TextBlock Text="{Binding Path=Age}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<TextBlock Text="Name:" />
<TextBox Text="{Binding Path=Name}" Grid.Column="1" />
<TextBlock Text="Age:" Grid.Row="1" />
<TextBox Grid.Row="1" Grid.Column="1" >
<TextBox.Text>
<Binding Path ="Age" UpdateSourceTrigger="LostFocus" >
<Binding.ValidationRules>
<local:AgeValidation />
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
</Grid>
</StackPanel>
