为什么我无法在 Windows 8.1 应用程序中删除 TextBox 文本？

Question

How do i remove text from a TextBox in Windows 8.1 App?? Whenever I click on the button, it adds "1" to the textbox :

private void button1_Click(object sender, RoutedEventArgs e)
        {

            textBox1.Text += 1;
        }

But when i use another button to replace/remove all text from textBox, it doesn't remove the text :

private void button0_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text = "";

        }

I also used textBox1.Text = string.Empty; but nothing happens.

Its a simple calculator windows 8.1 store app, Complete Code is given below :

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238

namespace App3
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {


        public MainPage()
        {
            this.InitializeComponent();



        }

        private void button0_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text = "";

            //or textBox1.Text = string.Empty; //It also doesn't work!!
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {

            textBox1.Text += 1;
        }

        private void button2_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 2;
        }

        private void button3_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 3;
        }

        private void button5_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 4;
        }

        private void button6_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 5;
        }

        private void button7_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 6;
        }

        private void button9_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 7;
        }

        private void button10_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 8;
        }

        private void button11_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 9;
        }

        private void button13_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += 0;
        }

        private void button14_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += ".";
        }

        private void button15_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "=";
        }

        private void button4_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "+";
        }

        private void button8_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "-";
        }

        private void button12_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "*";
        }

        private void button16_Click(object sender, RoutedEventArgs e)
        {
            textBox1.Text += "/";
        }

        private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
        {

        }

    }

}

So when I click button0, It does not clear the textbox.

MainPage.xaml:

<Page
    x:Class="App3.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App3"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Rectangle Fill="#FF707081" HorizontalAlignment="Left" Height="483" Margin="440,59,0,0" Stroke="Black" VerticalAlignment="Top" Width="456"/>
        <TextBox x:Name="textBox1" HorizontalAlignment="Left" Height="41" Margin="459,135,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="416" FontSize="24" FontFamily="Times New Roman" BorderBrush="#FF1F4BE2" TextChanged="textBox1_TextChanged" Text="Hello World"/>
        <Button x:Name="button2" Content="2" HorizontalAlignment="Left" Height="43" Margin="562,274,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button2_Click"/>
        <Button x:Name="button3" Content="3" HorizontalAlignment="Left" Height="43" Margin="668,274,0,0" VerticalAlignment="Top" Width="107" RenderTransformOrigin="0.495,1.465" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button3_Click"/>
        <Button x:Name="button5" Content="4" HorizontalAlignment="Left" Height="43" Margin="456,340,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button5_Click"/>
        <Button x:Name="button6" Content="5" HorizontalAlignment="Left" Height="43" Margin="562,340,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button6_Click"/>
        <Button x:Name="button7" Content="6" HorizontalAlignment="Left" Height="43" Margin="668,340,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button7_Click"/>
        <Button x:Name="button9" Content="7" HorizontalAlignment="Left" Height="43" Margin="456,410,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button9_Click"/>
        <Button x:Name="button1" Content="1" HorizontalAlignment="Left" Height="43" Margin="456,274,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button1_Click"/>
        <Button x:Name="button10" Content="8" HorizontalAlignment="Left" Height="43" Margin="562,410,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button10_Click"/>
        <Button x:Name="button11" Content="9" HorizontalAlignment="Left" Height="43" Margin="668,410,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button11_Click"/>
        <Button x:Name="button13" Content="0" HorizontalAlignment="Left" Height="43" Margin="456,477,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button13_Click"/>
        <Button x:Name="button14" Content="." HorizontalAlignment="Left" Height="43" Margin="562,477,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button14_Click"/>
        <Button x:Name="button15" Content="=" HorizontalAlignment="Left" Height="43" Margin="668,477,0,0" VerticalAlignment="Top" Width="107" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button15_Click"/>
        <Button x:Name="button0" Content="CLEAR" HorizontalAlignment="Left" Height="46" Margin="459,199,0,0" VerticalAlignment="Top" Width="419" Background="#FF1D1818" BorderBrush="#FF0D22F7"/>
        <Button x:Name="button4" Content="+" HorizontalAlignment="Left" Height="43" Margin="786,274,0,0" VerticalAlignment="Top" Width="92" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button4_Click"/>
        <Button x:Name="button8" Content="-" HorizontalAlignment="Left" Height="43" Margin="786,340,0,0" VerticalAlignment="Top" Width="92" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button8_Click"/>
        <Button x:Name="button12" Content="*" HorizontalAlignment="Left" Height="43" Margin="786,410,0,0" VerticalAlignment="Top" Width="92" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button12_Click"/>
        <Button x:Name="button16" Content="/" HorizontalAlignment="Left" Height="43" Margin="786,477,0,0" VerticalAlignment="Top" Width="92" Background="#FF1D1818" BorderBrush="#FF0D22F7" Click="button16_Click"/>
        <TextBlock HorizontalAlignment="Left" Height="30" Margin="462,76,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="413" FontSize="24" FontFamily="Times New Roman" Foreground="#FF718BE4">
            <Run Text="           "/>
            <Run Foreground="#FF0A0AE0" Text="Hussam's First Calculator"/>
        </TextBlock>
    </Grid>
</Page>

Answer 1

Look at the Xaml. The method to do the clear is orphaned and doesn't have a Click event subscribed to that method . You need to subscribe to it:

<Button x:Name="button0" Content="CLEAR" Click="button0_Click"/>

---

As an aside for most of the operations you could change them to call one centralized method which pulls the necessary text from the button which is calling it:

XAML:

<Button Content="1" Click="OperationsClick"/>
<Button Content="2" Click="OperationsClick"/>

CodeBehind

private void OperationsClick(object sender, RoutedEventArgs e)
{
    var btn = sender as Button;

    if (btn != null)
        textbox1.Text += btn.Content.ToString();
}