on get double from key down

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question

BrandonBoone-0673 asked Jun 24, '22 BrandonBoone-0673 answered Jun 24, '22

on get double from key down

How do I only get a double from a key down ?
so if the user type 4.56
I want to display 4.56
but if they type 4.35 then backspace
I want 4.3
and
not 4.36Back

here is my code:

 if (e.Key == Key.Enter || e.Key == Key.Return) return;
                 string letter;
                 if (e.Key == Key.OemPeriod)
                     letter = ".";
                 else
                     letter  = e.Key.ToString();
        
                 if (letter.Contains("D"))
                     letter = Regex.Replace(letter, "D", String.Empty);
                 SliderTxt.Text = SliderTxt.Text + letter;

dotnet-csharp dotnet-wpf-xaml

· 1

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HuiLiu-MSFT · Jun 24 at 08:54 AM

Hi,@BrandonBoone-0673 . Welcome Microsoft Q&A. Could you show the complete code relevant to your question? And what is your purpose? Can you try the method below to see if it works for you?
Xaml:

 <TextBox x:Name="tb" Text="{Binding Path=TransactionAmount,   Mode=TwoWay,   UpdateSourceTrigger=PropertyChanged}" 
                  Width="200" Height="105"  />

Codebehind:

 using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using System.Windows;
    
 public partial class MainWindow : Window, INotifyPropertyChanged
   {
      
     public MainWindow()
     {
       InitializeComponent();
     }
     private double _transactionAmount;
     public double TransactionAmount
     {
       get { return _transactionAmount; }
       set
       {
         if (_transactionAmount != value)
         {
           _transactionAmount = value;
           OnPropertyChanged();
         }
       }
    
     }
     public event PropertyChangedEventHandler PropertyChanged;
     protected void OnPropertyChanged([CallerMemberName] string propertyName = "") =>
       PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
   }

The result:

0 ·

image.png (3.4 KiB)

Answer 1 · 2022-06-24T09:10:36.847Z

HuiLiu-MSFT answered Jun 24, '22 BrandonBoone-0673 commented Jun 24, '22

Or do you want something like the following?
Xaml:

  <TextBox x:Name="tb2"   Width="200" Height="105"  PreviewTextInput="txt_PreviewTextInput"/>

Codebehind:

  private void txt_PreviewTextInput(object sender, TextCompositionEventArgs e)
     { 
      
       foreach (char ch in e.Text)
         if (!(Char.IsDigit(ch) || ch.Equals('.')))
         {
           e.Handled = true;
         }
     }

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Answer 2 · 2022-06-24T16:43:03.99Z

BrandonBoone-0673 answered Jun 24, '22

All
thanks for the help but I got it to work now.

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