Question

我是Prism MVVM的新手并尝试创建ViewModel属性，这些属性具有Model属性的支持字段。

public class SomeViewModel : BindableBase, INavigationAware
    {
        private Person model;
        public Person Model
        {
            get { return model; }
            set { SetProperty(ref model, value); }
        }

        public string DisplayName
        {
            get { return Model.DisplayName; }
            set { SetProperty(ref Model.DisplayName, value); }
        }

但它会在行生成编译器错误：

set { SetProperty(ref Model.DisplayName, value); }

“属性或索引器不能作为out或ref参数传递”。

那我该怎么做呢？

Answer 1

您需要手动提升OnPropertyChanged并在没有帮助程序的情况下进行设置。

<?php
foreach ($products as $product) {
    echo $product['price'].'<br>';
    echo $product['quantity'].'<br>';
    $subtotal = $product['price']*$product['quantity'];
    echo $subtotal.'<br>';

    echo $total; //??????
}
?>

Answer 2

您可以使用Reflection创建类似BindableBaseExtended的内容，这些内容来自Prism.Mvvm.BindableBase。

public class SomeViewModel : BindableBaseExtended
{
    private Person model;
    public Person Model
    {
        get { return model; }
        set { SetProperty(ref model, value); }
    }
    public string MyProperty
    {
        get { return Model.DisplayName; }
        set { SetProperty(Model, m => m.DisplayName, value); }
    }
}

public class BindableBaseExtended : BindableBase
{
    protected virtual bool SetProperty<TClass, TMember>(TClass target, Expression<Func<TClass, TMember>> expression, TMember value, [CallerMemberName] string propertyName = null)
    {
        var expr = (MemberExpression)expression.Body;
        var prop = (PropertyInfo)expr.Member;
        var propValue = prop.GetValue(target, null);
        if (object.Equals(propValue, value)) return false;

        prop.SetValue(target, value, null);
        this.RaisePropertyChanged(propertyName);
        return true;
    }
    protected virtual bool SetProperty<TClass, TMember>(TClass target, Expression<Func<TClass, TMember>> expression, TMember value, Action onChanged, [CallerMemberName] string propertyName = null)
    {
        var expr = (MemberExpression)expression.Body;
        var prop = (PropertyInfo)expr.Member;
        var propValue = prop.GetValue(target, null);
        if (object.Equals(propValue, value)) return false;

        prop.SetValue(target, value, null);
        onChanged?.Invoke();
        this.RaisePropertyChanged(propertyName);
        return true;
    }
}

Prism MVVM ViewModel属性支持字段作为模型的属性

2 个答案: