Question

我正在寻求有关如何在其中一项属性发生变化时收到通知的建议。

例如，假设我想将控件的文本绑定到WPF ViewModel中的FullAddress属性，只要其中一组属性发生更改，我就可以动态计算，例如StreetNumber，StreetName，Suburb，PostCode等。

我在想我需要将我的显示控件绑定到FullAddress属性，但是如果其中一个依赖属性发生更改，我该如何让它自动更新？我可以将属性的codebehind绑定到同一ViewModel上的多个其他属性吗？如果是这样的话？还有更好的方法吗？

Answer 1

假设您的类实现了INotifyPropertyChanged，那么您可以在任何属性设置器中进行通知。 E.g

    #region Implementation of INotifyPropertyChanged

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            Address.BeginEdit();
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }


    #endregion

    public string FirstLine
    {
        get { return firstLine; }
        set
        {
            firstLine = value;
            OnPropertyChanged("FirstLine");
            OnPropertyChanged("FullAddress");
        }
    }


    public string SecondLine
    {
        get { return secondLine; }
        set
        {
            secondLine= value;
            OnPropertyChanged("SecondLine");
            OnPropertyChanged("FullAddress");
        }
    }

    public string FullAddress
    {
        get { return firstLine + secondLine; }
    }

Answer 2

尝试这样的事情：

public class Address : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string address1;
    public string Address1
    {
        get { return address1; }
        set
        {
            address1 = value; 
            OnPropertyChanged("Address1");
            OnPropertyChanged("FullAddress");
        }
    }

    private string address2;
    public string Address2
    {
        get { return address2; }
        set
        {
            address2 = value; 
            OnPropertyChanged("Address2");
            OnPropertyChanged("FullAddress");
        }
    }

    private string town;
    public string Town
    {
        get { return town; }
        set
        {
            town = value; 
            OnPropertyChanged("Town");
            OnPropertyChanged("FullAddress");
        }
    }

    public string FullAddress
    {
        get { return string.Format("{0}, {1}, {2}", address1, address2, town);  }
    }

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

Answer 3

我认为你唯一的选择是让你的类的对象订阅他们自己的INPC事件并自动更改他们的依赖属性。工作流程将如下所示：

创建对象
对象订阅自己的INPC
依赖属性已更改
INPC订阅检测到FullAddress的相关属性已更改，并更新FullAddress值
FullAddress setter会触发自己的INPC事件
WPF检测到FullAddress已更改并更新了用户界面

更新：示例代码

class NotificationExample : INotifyPropertyChanged
{
    private string firstName;
    private string lastName;
    public event PropertyChangedEventHandler PropertyChanged;

    public string FirstName
    {
        get { return this.firstName; }

        set
        {
            this.firstName = value;
            this.OnPropertyChanged("FirstName");
        }
    }

    public string LastName
    {
        get { return this.lastName; }

        set
        {
            this.lastName = value;
            this.OnPropertyChanged("LastName");
        }
    }

    public string FullName
    {
        get { return string.Format("{0} {1}", this.firstName, this.lastName); }
    }

    public NotificationExample()
    {
        this.PropertyChanged += this.NotifyIfFullNameChanged;
    }

    private void OnPropertyChanged(string propertyName)
    {
        var handler = this.PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    private void NotifyIfFullNameChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "FirstName" || e.PropertyName == "LastName")
        {
            this.OnPropertyChanged("FullName");
        }
    }
}

Answer 4

您可以使用MultiBinding并且根本不使用FullAddress属性的修改：
如果您只需显示完整地址，则可以使用StringFormat

<TextBlock>
    <TextBlock.Text>
        <MultiBinding StringFormat="{}{0}, {1}">
            <Binding Path="City"/>
            <Binding Path="Street"/>
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

如果您希望允许用户编辑整个地址字符串然后将其拆分为部分，那么您需要实现IMultiValueConverter接口

当一组属性中的一个更改时，在代码中生成字符串

4 个答案: