我想用名稱“CurrentMoney”更新 WPF 表單上的標簽；我編寫了從“INotifyPropertyChanged”實現的類 Money。UPD：我通過創建 ViewModelBase 類更改為 MVVM 模式。仍然有“PropertyChaged”為空。如何解決它以及為什么會發生？Money.cs public class Money : ViewModelBase { private double currentMoney; public double CurrentMoney { get => currentMoney; set { currentMoney = value; OnPropertyChanged("CurrentMoney"); } } public Money() => currentMoney = 10000; public int addMoney(double count) { CurrentMoney += count; return 1; } public int subMoney(double count) { CurrentMoney -= count; if (currentMoney < 0) return 100; return 1; }}主窗口.cspublic partial class MainWindow : Window { public Money currentMoney; public MainWindow ( ) { InitializeComponent(); currentMoney = new Money(); CurrentMoney.DataContext = currentMoney; } private void Initialize() { CurrentMoney.Content = "Current money: " + currentMoney.CurrentMoney; CurrentPollution.Content = CurrentPollution.Content.ToString() + Pollution.CurrentPollution; Facktories.Content = Facktories.Content.ToString() + FactoriesList.Quantity; FactoriesPollution.Content = FactoriesPollution.Content.ToString() + FactoriesList.FullPolution; } private void MenuItem_Click(object sender, RoutedEventArgs e) { var buy = new BuySMTH(); this.Visibility = Visibility.Collapsed; buy.Show(); } private void Window_ContentRendered(object sender, EventArgs e) { Initialize(); } private void Tmp_Click(object sender, RoutedEventArgs e) { currentMoney.addMoney(1000); }
3 回答
倚天杖
TA貢獻1828條經驗 獲得超3個贊
您應該在屬性本身上實現接口。此外，在調用 PropertyChanged 事件時，您應該使用事件的本地（作用域）句柄以避免競爭條件。
public class Money : INotifyPropertyChanged {
double _currentMoney;
public event PropertyChangedEventHandler PropertyChanged;
public double CurrentMoney
{
get => _currentMoney;
set
{
_currentMoney = value;
OnPropertyChanged();
}
}
public Money() => CurrentMoney = 1000;
public int addMoney(double count) {
CurrentMoney += count;
return 1;
}
public int subMoney(double count) {
CurrentMoney -= count;
if (CurrentMoney < 0) { return 100; }
return 1;
}
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handle = PropertyChanged;
handle?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
編輯：為了節省一些打字時間，您還可以創建一個 ViewModelBase 類來處理較小的細節。
public abstract class ViewModelBase : INotifyPropertyChanged, IDisposable
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handle = PropertyChanged;
handle?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public virtual void Dispose() => PropertyChanged = null;
}
然后在實現 viewModel 類時，只需繼承自 base（但仍會通知屬性更改）。
public class MyClass : ViewModelBase
{
string _myField;
public string MyProperty
{
get => _myField;
set
{
_myField = value;
OnPropertyChanged();
}
}
}
注意：實際錯誤來自 [CallerMemberName] 屬性并從另一個方法中調用該方法。您可以傳入屬性名稱作為參數，也可以使用屬性本身的方法，而無需指定屬性名稱。
烙印99
TA貢獻1829條經驗 獲得超13個贊
NotifyPropertyChanged 將 propertyName 作為參數。默認值為空。
private void NotifyPropertyChanged([CallerMemberName] string propertyName = null) {
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}如果您想在 ui 上查看對“propertyName”的更改，可以使用 NotifyPropertyChanged("propertyName")。
對于您的示例，propertyName 是“CurrentMoney”
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