使用MVVM在WPF中连续显示当前时间 [英] Current Time display with continuous display in WPF using MVVM

问题描述

我想在屏幕上显示当前时间，并使用MVVM模式在WPF屏幕中进行连续更新。

I want to display current time on my screen with continuous updating in WPF screen using MVVM pattern.

我正在视图模型中编写这段代码

I am writing this code in my view model

// creating a property
private string _currentDateTime;
public string CurrentDateTime
{
    get
    {
        return _currentDateTime;
    }
    set
    {
        if (value != _currentDateTime)
        {
            _currentDateTime = value;
            this.RaisePropertyChanged(() => this.CurrentDateTime);
        }
    }
}

我写了这个方法

 public string GetCurrentDateTime()
 {
     try
     {
         DispatcherTimer timer = new DispatcherTimer(new TimeSpan(0, 0, 1), 
             DispatcherPriority.Normal, 
             delegate
             {
                 this.CurrentDateTime = DateTime.Now.ToString("HH:mm:ss");
             },
             this.Dispatcher);

             return CurrentDateTime;
     }
     catch
     {
         return CurrentDateTime;
     }
}

我将文本块与属性绑定，但显示异常，例如 this.CurrentDateTime 为 null 。

I binded my text block with property but it is showing exception as this.CurrentDateTime is null.

任何

推荐答案

我不确定 RaisePropertyChanged（（）=> ; this.CurrentDateTime）。

如果要处理MVVM属性更改通知，则此代码应在您的VM中

If it is to take care of MVVM property changed notifications, then this code should be in your VM

public event PropertyChangedEventHandler PropertyChanged;

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

那么您的集合应该是

set
{
    if (value != _currentDateTime)
    {
        _currentDateTime = value;
        OnPropertyChanged("CurrentDateTime");
    }
}

要不断更新时间，请使用 Timer

to continually update your time, use a Timer

然后您可以将间隔设置为1秒，并在每个计时器经过的事件上设置 CurrentDateTime

You can then set the interval to say 1 second and on each timer elapsed event set your CurrentDateTime

CurrentDateTime = DateTime.Now.ToString();

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