Question

我正在尝试创建一个简单的程序，您可以将汽车添加到列表中并查看make模型和年份。在我的xaml主窗口中，我有3个文本框来收集用户的信息：

<TextBox Text="{Binding NewCar.Model}"/>
<TextBox Text="{Binding NewCar.Make}"/>
<TextBox Text="{Binding NewCar.Year}"/>

然后用户点击＆＃34;添加＆＃34;按钮和汽车应该添加到列表中：

<Button Content="Add" Command="{Binding TouchCommand}" CommandParameter="{Binding NewCar}"/>

我已经验证了触摸命令正常添加汽车但是，似乎潜在的问题是文本框没有将输入到它们的内容绑定到NewCar对象的相应属性，因为当我点击添加按钮参数仍然为空。

这是add的执行方法：

    public void Execute(object parameter)
    {
        Car param = parameter as Car;

        if (param != null)
        {
            lib.List.Add(param);
            Console.WriteLine("{0} {1} {2}", param.Make, param.Model, param.Year);
        }
        else
        {
            Console.WriteLine("Param is null");
        }
    }

这是我的viewmodel中的相关代码：

namespace CarApp
{

public class Carvm : INotifyPropertyChanged
{
    private CarLib carLibrary;
    private Car currentCar;
    private DeleteCommand rmCommand;
    private AddCommand touchCommand;
    private Car newCar;

    public Car NewCar
    {
        get { return newCar; }
        set
        {
            newCar = value;
            NotifyPropertyChanged("NewCar");
        }
    }

    public Car CurrentCar
    {
        get { return currentCar; }
        set
        {
            currentCar = value;
            NotifyPropertyChanged("CurrentCar");
        }
    }

    public CarLib CarLibrary
    {
        get { return carLibrary; }
        set
        { 
            carLibrary = value;
            NotifyPropertyChanged("CarLibrary");
        }
    }

    public DeleteCommand RMCommand
    {
        get { return rmCommand; }
        set { rmCommand = value; }
    }

    public AddCommand TouchCommand
    {
        get { return touchCommand; }
        set { touchCommand = value; }
    }

    public Carvm()
    {
        carLibrary = new CarLib();

        carLibrary.List.Add(new Car("chevy", "corvette", "2016"));
        carLibrary.List.Add(new Car("ford", "gt", "2016"));
        carLibrary.List.Add(new Car("bmw", "m3", "2005"));

        rmCommand = new DeleteCommand(carLibrary);
        touchCommand = new AddCommand(carLibrary);

    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }
}
}

Answer 1

为什么要传递参数？您可以将TextBox绑定到ViewModel的属性，然后在add new car命令中，根据ViewModel中已有的信息创建一个新车。有很多方法可以做到这一点，但个人喜好是不要在按钮命令中传递参数，除非你必须这样做。祝你好运！

Answer 2

public Carvm()
{
    carLibrary = new CarLib();

    carLibrary.List.Add(new Car("chevy", "corvette", "2016"));
    carLibrary.List.Add(new Car("ford", "gt", "2016"));
    carLibrary.List.Add(new Car("bmw", "m3", "2005"));

    rmCommand = new DeleteCommand(carLibrary);
    touchCommand = new AddCommand(carLibrary);
    NewCar = new Car(); // this line is added

}

Answer 3

似乎问题是我没有任何地方可以获取信息，因为我没有在viewmodel中初始化newCar对象。我必须使用空字符串创建一个0参数构造函数，一切正常！

与xaml viewmodel连接

3 个答案: