Binding ValidationRule from TextBox to StatusBarItem and displaying the error message - wpf

Question

I am creating an application where I want to use validation rules, but on some screens there is not enough space to display the resulting error alongside the field which is in error, so I want to put it in a status bar at the bottom of the field.
This sample is from several bits I have pieced together from the web which gives a form which validates using different rules and displays the errors in different ways, but I cant see how to get the error message into the StatusBarItem using XAML. I feel sure there is a simple way to do it. Can anyone help me please?
The sample was written in VS2010 using Framework 4.0.
MainWindow.xaml
<Window x:Class="SampleValidation.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:c="clr-namespace:SWL.Libraries.SysText"
Title="Sample ValidationRule WPF" Height="350" Width="525"
Loaded="Window_Loaded" WindowStartupLocation="CenterScreen">
<Window.Resources>
<ControlTemplate x:Key="validationTemplate">
<!--
<TextBlock Foreground="Red" FontSize="20">***</TextBlock>
-->
<DockPanel LastChildFill="True">
<TextBlock DockPanel.Dock="Right" Foreground="Red" Margin="5" FontSize="8pt" Text="***" />
<AdornedElementPlaceholder />
</DockPanel>
</ControlTemplate>
<Style x:Key="textBoxInError1" TargetType="{x:Type 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>
<Style x:Key="textBoxInError2" TargetType="{x:Type TextBox}">
<Setter Property="Validation.ErrorTemplate">
<Setter.Value>
<ControlTemplate>
<DockPanel LastChildFill="True">
<TextBlock DockPanel.Dock="Right" Foreground="Red" Margin="5" FontSize="8pt"
Text="{Binding ElementName=MyAdorner, Path=AdornedElement.(Validation.Errors)[0].ErrorContent}" />
<Border BorderBrush="Red" BorderThickness="2">
<AdornedElementPlaceholder Name="MyAdorner" />
</Border>
</DockPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="true">
<Setter Property="ToolTip"
Value="{Binding RelativeSource={RelativeSource Self},
Path=(Validation.Errors)[0].ErrorContent}" />
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid>
<TextBlock Height="24" HorizontalAlignment="Left" Margin="36,73,0,0" Name="textBlock1"
Text="Node Address:" VerticalAlignment="Top" Width="87" />
<TextBlock Height="24" HorizontalAlignment="Left" Margin="36,112,0,0" Name="textBlock2"
Text="Node Name:" VerticalAlignment="Top" Width="78" />
<TextBox Height="24" HorizontalAlignment="Left" Margin="129,70,0,0" Name="textBox1"
VerticalAlignment="Top" Width="119" TextChanged="textBox1_TextChanged"
TabIndex="0" Style="{StaticResource textBoxInError2}"
Validation.ErrorTemplate="{StaticResource validationTemplate}">
<Binding Path="NodeAddress" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<c:NumberRangeRule Min="1" Max="100" />
</Binding.ValidationRules>
</Binding>
</TextBox>
<TextBox Height="24" HorizontalAlignment="Left" Margin="129,109,0,0" Name="textBox2"
VerticalAlignment="Top" Width="119" TextChanged="textBox2_TextChanged"
TabIndex="1" Style="{StaticResource textBoxInError2}">
<Binding Path="NodeName" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<c:NameFormatRule MinLength="6" MaxLength="9" />
</Binding.ValidationRules>
</Binding>
</TextBox>
<StatusBar Height="23" HorizontalAlignment="Stretch" Margin="0,0,0,0"
Name="myStatusBar" VerticalAlignment="Bottom">
<StatusBarItem x:Name="errorStatusBarItem" Content="No errors" />
</StatusBar>
<Button Content="Close" Height="29" HorizontalAlignment="Left" Margin="108,227,0,0"
Name="btnCLOSE" VerticalAlignment="Top" Width="85" Click="btnCLOSE_Click" TabIndex="3" />
<Button Content="Apply" Height="29" HorizontalAlignment="Left" Margin="297,227,0,0"
Name="btnAPPLY" VerticalAlignment="Top" Width="85" Click="btnAPPLY_Click" TabIndex="2" />
</Grid>
</Window>
MainWindow.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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.Navigation;
using System.Windows.Shapes;
namespace SampleValidation {
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window {
public int NodeAddress { get; set; }
public string NodeName { get; set; }
public bool IsAllLoaded { get; set; }
public MainWindow() {
NodeAddress = 1;
NodeName = "freddy";
IsAllLoaded = false;
InitializeComponent();
btnAPPLY.Visibility = System.Windows.Visibility.Hidden;
DataContext = this;
}
private void btnAPPLY_Click(object sender, RoutedEventArgs e) {
// if there are no format errors reported by the validation rules
Validator.ErrorText = "";
if (Validator.IsValid(this))
// Save the data
btnAPPLY.Visibility = System.Windows.Visibility.Hidden; // hide the button indicating nothing new to save
else
MessageBox.Show("Cant Save Changes - Error in form\r\n" + Validator.ErrorText, "Save not allowed", MessageBoxButton.OK, MessageBoxImage.Error);
}
private void btnCLOSE_Click(object sender, RoutedEventArgs e) {
if (btnAPPLY.Visibility != System.Windows.Visibility.Hidden) {
MessageBoxResult myAnswer = MessageBox.Show("Save Changes?", "Confirmation", MessageBoxButton.YesNoCancel);
if (myAnswer == MessageBoxResult.Cancel)
return;
if (myAnswer == MessageBoxResult.Yes)
btnAPPLY_Click(sender, e);
}
this.Close();
}
private void Window_Loaded(object sender, RoutedEventArgs e) {
IsAllLoaded = true;
}
private void ShowModified() {
if (IsAllLoaded)
btnAPPLY.Visibility = System.Windows.Visibility.Visible;
} // ShowModified
private void textBox2_TextChanged(object sender, TextChangedEventArgs e) {
ShowModified();
}
private void textBox1_TextChanged(object sender, TextChangedEventArgs e) {
ShowModified();
}
} // class MainWindow
public static class Validator {
public static string ErrorText { get; set; }
static Validator() {
ErrorText = "";
}
public static bool IsValid(DependencyObject parent) {
// Validate all the bindings on the parent
bool valid = true;
LocalValueEnumerator localValues = parent.GetLocalValueEnumerator();
while (localValues.MoveNext()) {
LocalValueEntry entry = localValues.Current;
if (BindingOperations.IsDataBound(parent, entry.Property)) {
Binding binding = BindingOperations.GetBinding(parent, entry.Property);
if (binding.ValidationRules.Count > 0) {
BindingExpression expression = BindingOperations.GetBindingExpression(parent, entry.Property);
expression.UpdateSource();
if (expression.HasError) {
ErrorText = expression.ValidationError.ErrorContent.ToString();
valid = false;
}
}
}
}
// Validate all the bindings on the children
System.Collections.IEnumerable children = LogicalTreeHelper.GetChildren(parent);
foreach (object obj in children) {
if (obj is DependencyObject) {
DependencyObject child = (DependencyObject)obj;
if (!IsValid(child)) {
valid = false;
}
}
}
return valid;
}
} // class Validator
ValidationRules.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Globalization;
using System.Windows.Controls;
namespace SWL.Libraries.SysText {
public class NumberRangeRule : ValidationRule {
private int _min;
private int _max;
public NumberRangeRule() { }
public int Min {
get { return _min; }
set { _min = value; }
}
public int Max {
get { return _max; }
set { _max = value; }
}
public override ValidationResult Validate(object value, CultureInfo cultureInfo) {
int val = 0;
try {
if (((string)value).Length > 0)
val = Int32.Parse((String)value);
} catch (Exception e) {
return new ValidationResult(false, "Illegal Characters or " + e.Message);
}
if ((val < Min) || (val > Max)) {
return new ValidationResult(false, "Please Enter Number in Range: " + Min + " - " + Max + ".");
} else {
return new ValidationResult(true, null);
}
}
}
public class NameFormatRule : ValidationRule {
private int _minLength;
private int _maxLength;
public NameFormatRule() { }
public int MinLength {
get { return _minLength; }
set { _minLength = value; }
}
public int MaxLength
get { return _maxLength; }
set { _maxLength = value; }
}
public override ValidationResult Validate(object value, CultureInfo cultureInfo) {
try {
if (((string)value).Length > 0) {
if (((string)value).Length < MinLength || ((string)value).Length > MaxLength)
return new ValidationResult(false, String.Format ("Enter a string of {0} to {1} characters in length", MinLength, MaxLength));
return new ValidationResult(true, null);
}
return new ValidationResult(true, null);
} catch (Exception e) {
return new ValidationResult(false, "Illegal Characters or " + e.Message);
}
}
}
}

Answer 1

UPDATE
I recently had to handle multiple error messages that were displayed when the mouse hovered an error icon. I made my viewmodel implement IDataErrorInfo. I then created a class-level Dictionary, keyed by a unique identifier for each control (I just used an enum), in my viewmodel to hold one error per control. Then I created a public property of type string and called it ErrorText. The getter of ErrorText iterates the errors dictionary and builds out all the errors into one string.
Here's an example, it may need tweaked. I know this is extremely simplified but should get you going in a direction. For complex validation, you can still validation using ValidationRule objects you create and then just check the IsValid property of the ValidationResult object returned.
// NOTE: The enum member name matches the name of the property bound to each textbox
public enum ControlIDs
{
TextBox1Value = 0,
TextBox2Value
}
public class MyViewModel : IDataErrorInfo
{
private readonly Dictionary<ControlIDs, string> errors;
public string ErrorText
{
get
{
if (errors.ContainsKey(ControlIDs.TextBox1) && errors.ContainsKey(ControlIDs.TextBox2))
{
return "Errors: " + errors[ControlsIDs.TextBox1] + ", " + errors[ControlsIDs.TextBox2];
}
if (errors.ContainsKey(ControlIDs.TextBox1))
{
return "Error: " + errors[ControlsIDs.TextBox1];
}
if (errors.ContainsKey(ControlIDs.TextBox2))
{
return "Error: " + errors[ControlsIDs.TextBox2];
}
}
}
public MyViewModel()
{
errors = new Dictionary<ControlIDs, string>();
}
private void UpdateErrorCollection(ControlIDs fieldKey, string error)
{
if (errors.ContainsKey(fieldKey))
{
errors[fieldKey] = error;
}
else
{
errors.Add(fieldKey, error);
}
OnPropertyChanged("ErrorText");
}
#region IDataErrorInfo
public string Error
{
get { throw new NotImplementedException(); }
}
public string this[string columnName]
{
string error = string.Empty;
if (columnName == ControlIDs.TextBox1Value.ToString())
{
if (string.IsNullOrWhiteSpace(TextBox1Value))
{
error = "TextBox1 must contain a value";
UpdateErrorCollection(ControlIDs.TextBox1Value, error);
}
else
{
errors.Remove(ControlIDs.TextBox1Value);
}
}
else if (columnName == ControlIDs.TextBox2Value))
{
if (string.IsNullOrWhiteSpace(TextBox2Value))
{
error = "TextBox2 must contain a value";
UpdateErrorCollection(ControlIDs.TextBox2Value, error);
}
else
{
errors.Remove(ControlIDs.TextBox2Value);
}
}
// returning null indicates success
return !string.IsNullOrWhiteSpace(error) ? error : null;
}
#endregion
}
Now just bind your StatusBarItem TextBlock to the ErrorText property.