UWP Textbox Validation for any special characters

Question

UWP Textbox Validation ...

Need a simple Example for UWP Textbox Validation if any special characters entered.

I dont want to Use any third party dll's nor nugget package..

Accepted Answer

Hi, see code in C#:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Windows.UI.Xaml.Controls;

namespace App01
{
  public class ViewModel
  {
    public Data View { get; } = new Data();
  }

  public class Data : IDataErrorInfo, INotifyPropertyChanged
  {

    private string _name = string.Empty;
    public string Name
    {
      get => this._name;
      set
      {
        this._name = value;
        errorMessages[nameof(Name)] = this[nameof(Name)];
        OnPropertyChanged();
      }
    }

    private int _age = 0;
    private string _ageString = null;
    public object Age
    {
      get => this._age.ToString();
      set
      {
        if (value == null) this._ageString = "?";
        else
        {
          this._ageString = value.ToString();
          int.TryParse(value.ToString(), out this._age);
          errorMessages[nameof(Age)] = this[nameof(Age)];
          OnPropertyChanged();
        }
      }
    }

    private readonly Dictionary errorMessages = new Dictionary();

    public string Error
    {
      get
      {
        var result = string.Empty;
        foreach (KeyValuePair< String, String> em in errorMessages)
          if (!string.IsNullOrEmpty(em.Value))
            result += (String.IsNullOrEmpty(result)) ? em.Value : Environment.NewLine + em.Value;
        return result;
      }
    }

    public string this[string columnName]
    {
      get
      {
        var result = string.Empty;
        switch (columnName)
        {
          case "Name":
            if (String.IsNullOrEmpty(Name)) result = "Name may not be null or empty";
            break;
          case "Age":
            if (String.IsNullOrEmpty(this._ageString)) result = "Age may not be null or empty";
            else if (this._age < 18 || this._age > 65) result = "Age must be beetween 18 an 65";
            break;
        }
        return result;
      }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    internal void OnPropertyChanged([CallerMemberName] string propName = "") =>
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
  }
}

using System;
using System.ComponentModel;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236

namespace App01
{
  public sealed partial class Page01UC1 : UserControl
  {
    public Page01UC1()
    {
      this.InitializeComponent();
    }

    public static readonly DependencyProperty DataObjectProperty =
    DependencyProperty.RegisterAttached("DataObject", typeof(object),
                                        typeof(Page01UC1), new PropertyMetadata(null, PropChanged));

    public static object GetDataObject(DependencyObject obj) => obj.GetValue(DataObjectProperty);
    public static void SetDataObject(DependencyObject obj, object value) => obj.SetValue(DataObjectProperty, value);

    public static readonly DependencyProperty PropertyNameProperty =
    DependencyProperty.RegisterAttached("PropertyName", typeof(String),
                                        typeof(Page01UC1), new PropertyMetadata(string.Empty, PropChanged));

    public static string GetPropertyName(DependencyObject obj) => obj.GetValue(PropertyNameProperty).ToString();

    public static void SetPropertyName(DependencyObject obj, string value) => obj.SetValue(PropertyNameProperty, value);

    public string PropertyName { get; set; }

    private static void PropChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
      var uc = d as Page01UC1;
      var data = GetDataObject(d) as INotifyPropertyChanged;
      var name = GetPropertyName(d);
      if (uc == null || data == null || name == null) return;
      uc.PropertyName = name;
      data.PropertyChanged += uc.Data_PropertyChanged;
      uc.Data_PropertyChanged(data, null);
    }
    private void Data_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
      var t = sender.GetType();
      var pi = t.GetProperty(PropertyName);
      this.tbox.Text = pi.GetValue(sender).ToString();
      pi = t.GetProperty("Item");
      this.tblock.Text = pi.GetValue(sender, new object[] { PropertyName }).ToString();
      this.border1.Visibility = (String.IsNullOrEmpty(this.tblock.Text) ? Visibility.Collapsed : Visibility.Visible);
      this.border2.Visibility = this.border1.Visibility;
    }
  }
}

Answer

You could define your XAML as below: I suggest to use another Border around the TextBox to highlight the error because TextBox.BorderBrush is used by visual states and have different colors when TextBox when takes focus, is disabled, when the mouse is over, ecc...

Here TextBox_OnTextChanged definition:

private void TextBox_OnTextChanged(object sender, TextChangedEventArgs e)
{
    var specialChars = new []{'#', '%', '^'};

    var textBox = (TextBox) sender;
    string textBoxText = textBox.Text;
    char[] mistakes = specialChars.Where(c => textBoxText.Contains(c)).ToArray();
    if (textBoxText.Contains("#"))
    {
        TextBoxBorder.BorderBrush = new SolidColorBrush(Colors.Red);
        ErrorTextBlock.Text = $"Characters {string.Join(", ", mistakes)} not allowed!";
        ErrorTextBlock.Visibility = Visibility.Visible;
    }
    else
    {
        TextBoxBorder.BorderBrush = null;
        ErrorTextBlock.Visibility = Visibility.Collapsed;
    }
}

Answer

Hi, you can build your own UserControl to bind data object with IDataError like in following simple demo:

-------------------------------------------------------

Namespace App01  
  
  Public Class ViewModel  
    Public ReadOnly Property View As New Data  
  End Class  
  
  Public Class Data  
    Implements IDataErrorInfo, INotifyPropertyChanged  
  
    Private _name As String = String.Empty  
    Public Property Name As String  
      Get  
        Return Me._name  
      End Get  
      Set  
        Me._name = Value  
        errorMessages(NameOf(Name)) = Item(NameOf(Name))  
        OnPropertyChanged()  
      End Set  
    End Property  
  
    Private _age As Integer = 0  
    Private _ageString As String = Nothing  
    Public Property Age As Object  
      Get  
        Return Me._age.ToString()  
      End Get  
      Set(value As Object)  
        If value Is Nothing Then  
          Me._ageString = "?"  
  
        Else  
          Me._ageString = value.ToString()  
          Integer.TryParse(value.ToString(), Me._age)  
          errorMessages(NameOf(Age)) = Item(NameOf(Age))  
          OnPropertyChanged()  
        End If  
      End Set  
    End Property  
  
    Private ReadOnly errorMessages As Dictionary(Of String, String) = New Dictionary(Of String, String)  
  
    Private ReadOnly Property IDataErrorInfo_Error As String Implements IDataErrorInfo.Error  
      Get  
        Dim result = String.Empty  
        For Each em In errorMessages  
          If Not String.IsNullOrEmpty(em.Value) Then  
            result += If(String.IsNullOrEmpty(result), em.Value, Environment.NewLine + em.Value)  
          End If  
        Next  
        Return result  
      End Get  
    End Property  
  
    Default Public ReadOnly Property Item(columnName As String) As String Implements IDataErrorInfo.Item  
      Get  
        Dim result = String.Empty  
        Select Case columnName  
          Case "Name" : If (String.IsNullOrEmpty(Name)) Then result = "Name may not be null or empty"  
          Case "Age"  
            If (String.IsNullOrEmpty(Me._ageString)) Then  
              result = "Age may not be null or empty"  
            ElseIf Me._age < 18 OrElse Me._age > 65 Then  
              result = "Age must be beetween 18 an 65"  
            End If  
        End Select  
        Return result  
      End Get  
    End Property  
  
    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged  
    Protected Sub OnPropertyChanged( Optional propertyName As String = "")  
      RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))  
    End Sub  
  
  End Class  
  
End Namespace

-------------------------------------------------------------

-------------------------------------------------

Imports System.Reflection  
  
Namespace App01  
  
  Public NotInheritable Class Page01UC1  
    Inherits UserControl  
  
    Public Shared ReadOnly DataObjectProperty As DependencyProperty =  
    DependencyProperty.RegisterAttached("DataObject", GetType(Object),  
                                        GetType(Page01UC1), New PropertyMetadata(Nothing, AddressOf PropChanged))  
  
    Public Shared Function GetDataObject(obj As DependencyObject) As Object  
      Return obj.GetValue(DataObjectProperty)  
    End Function  
  
    Public Shared Sub SetDataObject(obj As DependencyObject, value As Object)  
      obj.SetValue(DataObjectProperty, value)  
    End Sub  
  
    Public Shared ReadOnly PropertyNameProperty As DependencyProperty =  
    DependencyProperty.RegisterAttached("PropertyName", GetType(String),  
                                        GetType(Page01UC1), New PropertyMetadata(String.Empty, AddressOf PropChanged))  
  
    Public Shared Function GetPropertyName(obj As DependencyObject) As String  
      Return CType(obj.GetValue(PropertyNameProperty), String)  
    End Function  
  
    Public Shared Sub SetPropertyName(obj As DependencyObject, value As String)  
      obj.SetValue(PropertyNameProperty, value)  
    End Sub  
  
    Public Property PropertyName As String  
  
    Private Shared Sub PropChanged(d As DependencyObject, e As DependencyPropertyChangedEventArgs)  
      Dim uc = TryCast(d, Page01UC1)  
      Dim data = TryCast(GetDataObject(d), INotifyPropertyChanged)  
      Dim name = GetPropertyName(d)  
      If uc Is Nothing OrElse data Is Nothing OrElse name Is Nothing Then Exit Sub  
      uc.PropertyName = name  
      AddHandler data.PropertyChanged, AddressOf uc.Data_PropertyChanged  
      uc.Data_PropertyChanged(data, Nothing)  
    End Sub  
  
    Private Sub Data_PropertyChanged(sender As Object, e As PropertyChangedEventArgs)  
      Dim t As Type = sender.GetType  
      Dim pi As PropertyInfo = t.GetProperty(PropertyName)  
      Me.tbox.Text = pi.GetValue(sender).ToString  
      pi = t.GetProperty("Item")  
      Me.tblock.Text = pi.GetValue(sender, New Object() {PropertyName}).ToString  
      Me.border1.Visibility = If(String.IsNullOrEmpty(Me.tblock.Text), Visibility.Collapsed, Visibility.Visible)  
      Me.border2.Visibility = Me.border1.Visibility  
    End Sub  
  
  End Class  
  
End Namespace

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UWP Textbox Validation for any special characters

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