To get it done only with XAML you need to add Validation Rules for individual properties. But i would recommend you to go with code behind approach. In your code, define your specifications in properties setters and throw exceptions when ever it doesn't compliance to your specifications. And use error template to display your errors to user in UI. Your XAML will look like this
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style x:Key="CustomTextBoxTextStyle" TargetType="TextBox">
<Setter Property="Foreground" Value="Green" />
<Setter Property="MaxLength" Value="40" />
<Setter Property="Width" Value="392" />
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="True">
<Trigger.Setters>
<Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self},Path=(Validation.Errors)[0].ErrorContent}"/>
<Setter Property="Background" Value="Red"/>
</Trigger.Setters>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid>
<TextBox Name="tb2" Height="30" Width="400"
Text="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnExceptions=True}"
Style="{StaticResource CustomTextBoxTextStyle}"/>
</Grid>
Code Behind:
public partial class MainWindow : Window
{
private ExampleViewModel m_ViewModel;
public MainWindow()
{
InitializeComponent();
m_ViewModel = new ExampleViewModel();
DataContext = m_ViewModel;
}
}
public class ExampleViewModel : INotifyPropertyChanged
{
private string m_Name = "Type Here";
public ExampleViewModel()
{
}
public string Name
{
get
{
return m_Name;
}
set
{
if (String.IsNullOrEmpty(value))
{
throw new Exception("Name can not be empty.");
}
if (value.Length > 12)
{
throw new Exception("name can not be longer than 12 charectors");
}
if (m_Name != value)
{
m_Name = value;
OnPropertyChanged("Name");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}