C#中向List<string>赋值报错

在WPF中我声明了一个类用作动态绑定，其中我声明了一个List类型的属性，但是在后台代码中我对其直接进行赋值报错，内容是”未将对象引用设置到对象的实例“，编译是能通过的，如果想让其正确赋值应该怎么修改呢

这是我声明的一个用来动态绑定的类

class BindingProperty : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged(string propertyName) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));      

        private List<string> _readDataTextBlock;

        public List<string> ReadDataTextBlock 
        {
            get { return _readDataTextBlock; }
            set { _readDataTextBlock = value;OnPropertyChanged(nameof(ReadDataTextBlock)); }
        }
    }

我直接用“0000”做测试，结果报错

public partial class MainWindow : Window
 {
        private BindingProperty _bindingProperty = new BindingProperty();
        public MainWindow()
        {
            this.DataContext = _bindingProperty;
            InitializeComponent();
        }
        private void ButtonReadByte_Click(object sender, RoutedEventArgs e)
        {
            _bindingProperty.ReadDataTextBlock.Add("0000");
        }
}

没有初始化add报错了
private List _readDataTextBlock = new;