WPF data validation and display error message IDataErrorInfo and error templates - wpf-controls

Question

How to do WPF data validation for error and display error message using IDataErrorInfo and error templates

Answer 1

ViewModel: IDataViewModel.cs
using GalaSoft.MvvmLight;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace IDataErrorInfo_InputValidation.ViewModel
{
class IDataViewModel:ViewModelBase,IDataErrorInfo
{
public string FirstName { get; set; }
public string LastName { get; set; }
public int Age { get; set; }
public string Error
{
get { throw new NotImplementedException(); }
}
public string this[string columnName]
{
get
{
string result = null;
if (columnName == "FirstName")
{
if (string.IsNullOrEmpty(FirstName))
result = "Please Enter Your FirstName";
}
if(columnName == "LastName")
{
if (string.IsNullOrEmpty(LastName))
result = "Please Enter Your LastName";
}
if(columnName == "Age")
{
if(Age <= 0 || Age >= 99)
result ="Please Enter Valid Age";
}
return result;
}
}
}
}
xaml : IDataView.xaml
<Window x:Class="IDataErrorInfo_InputValidation.View.IDataView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="IDataView" Height="300" Width="300">
<Window.Resources>
<!-- Error template for changing behaviour -->
<ControlTemplate x:Key="ErrorTemplate">
<DockPanel LastChildFill="True">
<Border BorderBrush="Red" BorderThickness="1">
<AdornedElementPlaceholder />
</Border>
</DockPanel>
</ControlTemplate>
<Style TargetType="TextBox">
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="true">
<Setter Property="ToolTip" Value="{Binding RelativeSource={x:Static RelativeSource.Self},Path=(Validation.Errors)[0].ErrorContent}"/>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid HorizontalAlignment="Center">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBox Text="{Binding FirstName,Mode=TwoWay,ValidatesOnDataErrors=True,NotifyOnValidationError=True,ValidatesOnExceptions=True}" Height="20" Width="100" Margin="10"/>
<TextBox Text="{Binding LastName,Mode=TwoWay,ValidatesOnDataErrors=True,NotifyOnValidationError=True,ValidatesOnExceptions=True}" Grid.Row="1" Height="20" Width="100" Margin="10" />
<TextBox Grid.Row="2" Text="{Binding Age,Mode=TwoWay,ValidatesOnDataErrors=True,NotifyOnValidationError=True,ValidatesOnExceptions=True}" Height="20" Width="100" Margin="10"/>
<!--<TextBox Grid.Row="2" Height="20" Width="100" Margin="10"/>-->
<TextBox Grid.Row="3" Height="20" Width="100" Margin="10"/>
</Grid>
</Window>
IDataViewXaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
namespace IDataErrorInfo_InputValidation.View
{
/// <summary>
/// Interaction logic for IDataView.xaml
/// </summary>
public partial class IDataView : Window
{
public IDataView()
{
InitializeComponent();
DataContext = new ViewModel.IDataViewModel();
}
}
}