WPF绑定在按钮上不会触发命令

Question

我正在尝试对按钮进行简单的绑定，该按钮我以前使用过并且运行良好。但是现在在新的解决方案中，它不会触发绑定命令。 这是XAML：

<Window x:Class="MusicPlayer.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:MusicPlayer"
        mc:Ignorable="d"
        Title="MainWindow" Height="300" Width="400">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="auto"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="100"/>
            <ColumnDefinition Width="200"/>
            <ColumnDefinition Width="100"/>

        </Grid.ColumnDefinitions>

        <TextBlock Text="{Binding Name}" Grid.Row="1" Grid.Column="1"/>
        <ListView Grid.Row="1" Grid.Column="2" DataContext="{Binding Musics}" 
   SelectedItem="{Binding CurrentMusic}">
            <ListView.View>
                <GridView>
                    <GridViewColumn DisplayMemberBinding="{Binding Name}" />
                </GridView>
            </ListView.View>
        </ListView>

        <Button Content="Next"  Grid.Row="3" Grid.Column="3" Command="{Binding 
   nextCommand}"/>
        <Button Content="Previous"  Grid.Row="3" Command="{Binding 
   previousCommand}"/>
        <Button Content="Play"  Grid.Row="3" Grid.Column="1" Command="{Binding 
   playCommand}"/>
        <Button Content="Open"  Grid.Row="0" Grid.Column="0" Command="{Binding 
   openCommand}"/>
    </Grid>
   </Window>

这是视图模型：

using Microsoft.Win32;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MusicPlayer 
{
    public class MusicPlayerViewModel : INotifyPropertyChanged
    {

        private Music _currentMusic;
        public DelegateCommand nextCommand;
        public DelegateCommand previousCommand;
        public DelegateCommand playCommand;
        public DelegateCommand openCommand;

        public Music CurrentMusic
        {
            get { return _currentMusic; }
            set
            {
                if(_currentMusic != value)
                {
                    _currentMusic = value;
                    OnPropertyChanged("CurrentMusic");
                }
            }

        }
        public ObservableCollection<Music> Musics = new ObservableCollection<Music>();

        public MusicPlayerViewModel()
        {
            CurrentMusic = new Music { Name = "X", PathString = "Y" };
            Musics.Add(CurrentMusic);
            nextCommand = new DelegateCommand(param => DoNext());
            previousCommand = new DelegateCommand(param => DoPrevious());
            playCommand = new DelegateCommand(param => DoPlay());
            openCommand = new DelegateCommand(param => DoOpen());
        }


        public void DoNext()
        {
            CurrentMusic = new Music();
            OnPropertyChanged("DoNext");

        }
        public void DoPrevious()
        {

            OnPropertyChanged("DoPrevious");

        }
        public void DoPlay()
        {

            OnPropertyChanged("DoPlay");

        }
        public void DoOpen()
        {
            OpenFileDialog dialog = new OpenFileDialog();
            dialog.Filter = "Mp3 files (*.mp3)|*.mp3|All files (*.*)|*.*";
            Nullable<bool> result = dialog.ShowDialog();

            if (result == true)
            {
                string filename = dialog.FileName;

                CurrentMusic.Name = filename;
            }
            OnPropertyChanged("DoOpen");

        }


        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(String property)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(property));
            }
        }
    }
}

由于某些原因，只有文本块绑定有效，而其他都不起作用，这很奇怪，因为我在以前的解决方案中一直使用此模板，这很好。我在app.xaml.cs中将窗口的数据上下文设置为MusicPlayerViewModel，所以这应该不是问题。我将不胜感激。