Question

我有一个使用MVVM模式的应用程序，我想在用户填写信息时实现验证。例如，如果min大于max，我想在视图中禁用该按钮。

我在模型中实现了IDataErrorInfo。这是我的模特：

public class MyModel : IDataErrorInfo, INotifyPropertyChanged
{
    private string stock;
    public string Stock
    {
        get { return stock; }
        set { stock = value; }
    }

    private double min;
    public double Min
    {
        get { return min; }
        set { min = value; OnPropertyChange("Min"); }
    }

    private double max;
    public double Max
    {
        get { return max; }
        set { max = value; OnPropertyChange("Max"); }
    }

    public string Error
    {
        get { throw new NotImplementedException(); }
    }

    public string this[string columnName]
    {
        get
        {
           string  error = string.Empty;
            if (columnName == "Min" || columnName == "Max")
            {
                if (Min > Max)
                {
                    error = "Min can't be greater than Max";
                }
            }
            return error;
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChange(string name)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }
}

我的ViewModel有一个MyModel（绑定到DataGrid）的集合和一个名为CanUpdate的布尔属性。在我的视图中，此CanUpdate绑定到更新按钮的IsEnabled属性。

public class MyViewModel : INotifyPropertyChanged
{
    private ObservableCollection<MyModel> stocks;
    public ObservableCollection<MyModel> Stocks
    {
        get { return stocks; }
        set { stocks = value; }
    }

    private bool canUpdate = true;
    public bool CanUpdate
    {
        get { return canUpdate; }
        set { canUpdate = value; }
    }        

    public MyViewModel()
    {
        AddStocks();
    }

    public void AddStocks()
    {
        Stocks = new ObservableCollection<MyModel>();
        Stocks.Add(new MyModel() { Stock ="Stock 1", Min = 10, Max=20 });
        Stocks.Add(new MyModel() { Stock = "Stock 2", Min = 5, Max = 15 });
        Stocks.Add(new MyModel() { Stock = "Stock 3", Min = 6, Max = 25 });
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChange(string name)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }

用户可以编辑DataGrid中的Min和Max值。在MyModel中引发错误时编辑时必须更新MyViewModel中的CanUpdate属性。请指导我实现这一目标。

Answer 1

在视图模型中，将项目添加到其PropertyChanged事件的集合挂钩时。在处理程序中分析Error属性并相应地修改CanUpdate。

在模型中引发错误时传递ViewModel

1 个答案: