如何使用清除按钮清除WPF MVVM中的文本框

Question

好的，我想通过点击按钮来清除文本框中的文本。两者都放在XAML代码中的第一个堆栈面板中。我试图使它与命令和绑定工作，但我只是不能使它工作…有什么建议吗?SqlQueryCommand绑定清除按钮，SqlQueryString绑定文本框。

Vievmodel:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
using WpfMVVM.Commands;
namespace PoC.ViewModels
{
class MainWindowViewModel
{
public RelayCommand ClearSqlQueryCommand { get; private set; }
public RelayCommand ClearFilterCommand { get; private set; }
public RelayCommand ClearFilterByIdCommand { get; private set; }
public event PropertyChangedEventHandler PropertyChanged;
private string sqlQueryString;
private string filterString;
private string filterByIdString;
public string SqlQueryString
{
get
{
return sqlQueryString;
}
set
{
sqlQueryString = value;
OnPropertyChanged(nameof(SqlQueryString));
}
}
public string FilterString
{
get
{
return filterString;
}
set
{
filterString = value;
OnPropertyChanged(nameof(FilterString));
}
}
public string FilterByIdString
{
get
{
return filterByIdString;
}
set
{
filterByIdString = value;
OnPropertyChanged(nameof(FilterByIdString));
}
}
public MainWindowViewModel()
{
ClearSqlQueryCommand = new RelayCommand(ClearSqlQuery, CanClearSqlQuery);
ClearFilterCommand = new RelayCommand(ClearFilter, CanClearFilter);
ClearFilterByIdCommand = new RelayCommand(ClearFilterById, CanClearFilterById);
}
protected void OnPropertyChanged([CallerMemberName] string name = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
}
public void ClearSqlQuery(object parameter)
{
SqlQueryString = string.Empty;
}
public bool CanClearSqlQuery(object parameter)
{
return true;
}
public void ClearFilter(object parameter)
{
}
public bool CanClearFilter(object parameter)
{
return true;
}
public void ClearFilterById(object parameter)
{
}
public bool CanClearFilterById(object parameter)
{
return true;
}
}
}

RelayCommand:

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Input;
namespace WpfMVVM.Commands
{
public class RelayCommand : ICommand
{
Action<object> _execute;
Func<object, bool> _canExecute;

public RelayCommand(Action<object> execute, Func<object, bool> canExecute)
{
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
if (_canExecute != null)
{
return _canExecute(parameter);
}
else
{
return false;
}
}
public event EventHandler CanExecuteChanged
{
add
{
CommandManager.RequerySuggested += value;
}
remove
{
CommandManager.RequerySuggested -= value;
}
}
public void Execute(object parameter)
{
_execute(parameter);
}
}
}

XAML:

<Window x:Class="PoC.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:PoC"
xmlns:viewModels="clr-namespace:PoC.ViewModels"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Window.DataContext>
<viewModels:MainWindowViewModel/>
</Window.DataContext>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"/>
<ColumnDefinition Width="3*"/>
</Grid.ColumnDefinitions>
<TreeView>
</TreeView>

<Grid Grid.Column="1">
<Grid.RowDefinitions>
<RowDefinition Height="2*" />
<RowDefinition Height="1*"/>
<RowDefinition Height="5*"/>
</Grid.RowDefinitions>
<Border Grid.Row="0" BorderThickness="0 0 0 1" BorderBrush="Black"/>
<StackPanel Grid.Row="0" Orientation="Horizontal" VerticalAlignment="Center" HorizontalAlignment="Center">
<TextBox Text="{Binding SqlQueryString, UpdateSourceTrigger=PropertyChanged}" Height="30" Width="450" TextAlignment="Center"/>
<Button Content="Execute" Margin="10 0" Padding="5 0"/>
<Button Content="Clear" Padding="5 0" Command="{Binding ClearSqlQueryCommand}"/>
</StackPanel>
<StackPanel Grid.Row="1" Orientation="Horizontal" VerticalAlignment="Center" HorizontalAlignment="Center">
<TextBox Text="{Binding FilterString}" Grid.Row="0" Height="30" Width="200"/>
<Button Content="Filter" Margin="10 0" Padding="5 0"/>
<Button Content="Clear" Padding="5 0" Margin="0 0 115 0"/>
<TextBox Text="{Binding FilterByIdString}" Grid.Row="0" Height="30" Width="100"/>
<Button Content="Filter" Margin="10 0 0 0" Padding="5 0"/>
</StackPanel>
<DataGrid Grid.Row="2" VerticalScrollBarVisibility="Visible" BorderThickness="0 1 1 1"/>
</Grid>


</Grid>

Answer 1

您似乎在MainWindowViewModel类中缺少了: INotifyPropertyChanged。

Answer 2

您可以通过将其值设置为"来轻松地做到这一点。

texbox.Text="";