WPF4/C＃ - System.StackOverflowException崩潰應用程序

Question

下面您可以看到我的.xaml.cs代碼。該應用打開罰款。有4個用戶可以更改的文本框。當您在文本框中編輯默認值之一，然後單擊以不選中它時，該應用程序會崩潰並顯示System.StackOverflowException錯誤，並說我的get {}或Calc（）函數有無限循環或遞歸，取決於哪個文本框被編輯。我希望應用程序在每次未編輯文本框時根據Calc（）函數計算數字。我也想爲文本框定義一些起始值，但還沒有弄清楚如何去做。

任何想法如何修復循環錯誤和初始值定義？

中的.xaml代碼的文本框遵循此模式：Text="{Binding DistanceBox}"

完整背後代碼如下：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Windows; 
using System.Windows.Controls; 
using System.Windows.Data; 
using System.Windows.Documents; 
using System.Windows.Input; 
using System.Windows.Media; 
using System.Windows.Media.Imaging; 
using System.Windows.Navigation; 
using System.Windows.Shapes; 
using System.ComponentModel; 

namespace ConverterApp 
{ 
    public partial class MainWindow : Window 
    { 
     public MainWindow() 
     { 
      InitializeComponent(); 
      DataContext = new Variables(); 
     } 
    } 

    public class Variables : INotifyPropertyChanged 
    { 
     // Declare the PropertyChanged event. 
     public event PropertyChangedEventHandler PropertyChanged; 

     private double m_distanceBox; 
     public double DistanceBox 
     { 
      get { return m_distanceBox; } 
      set 
      { 
       //If value hasn't changed, don't do anything 
       //if (m_distanceBox == value) 
       // return; 
       m_distanceBox = value; 
       // modify calc to read the text values 
       Calc(); 
       // Call NotifyPropertyChanged when the source property 
       // is updated. 
       //if(PropertyChanged!= null) 
        NotifyPropertyChanged("DistanceBox"); 
      } 
     } 

     private double m_widthBox; 
     public double WidthBox 
     { 
      get { return m_widthBox; } 
      set 
      { 
       m_widthBox = value; 
       // modify calc to read the text values 
       Calc(); 
       // Call NotifyPropertyChanged when the source property 
       // is updated. 
       NotifyPropertyChanged("WidthBox"); 
      } 
     } 

     private double m_lengthBox; 
     public double LengthBox 
     { 
      get { return m_lengthBox; } 
      set 
      { 
       m_lengthBox = value; 
       // modify calc to read the text values 
       Calc(); 
       // Call NotifyPropertyChanged when the source property 
       // is updated. 
       NotifyPropertyChanged("LengthBox"); 
      } 
     } 

     private double m_lensBox; 
     public double LensNeeded 
     { 
      get { return m_lensBox; } 
      set 
      { 
       m_lensBox = value; 
       // modify calc to read the text values 
       Calc(); 
       // Call NotifyPropertyChanged when the source property 
       // is updated. 
       NotifyPropertyChanged("LensNeeded"); 
      } 
     } 

     public void Calc() 
     { 
      double WidthBased = 2.95 * (DistanceBox/WidthBox); 
      double LengthBased = 3.98 * (DistanceBox/LengthBox); 

      if (WidthBased < LengthBased) 
      { 
       LensNeeded = Math.Round(WidthBased,2); 
      }else{ 
       LensNeeded = Math.Round(LengthBased,2); 
      } 
     } 

     // NotifyPropertyChanged will raise the PropertyChanged event, 
     // passing the source property that is being updated. 
     public void NotifyPropertyChanged(string propertyName) 
     { 
      if (PropertyChanged != null) 
      { 
       PropertyChanged(this, 
        new PropertyChangedEventArgs(propertyName)); 
      } 
     } 
    } 
} 

Answer 1

在你的調用CalcLensNeeded二傳手，鈣，進而設置LensNeeded，設置者LensNeeded調用Calc等，這個循環性導致StackOverflow。

不要在setter中計算屬性，使相應的屬性爲「虛擬」（即時計算值，而不是從後臺字段獲取值）。

public double WidthBased 
{ 
    get { return 2.95 * (DistanceBox/WidthBox); } 
} 

爲了使綁定到這種特性更新，你可以提高性能在所有相關的屬性制定者改變的事件，這裏將是DistanceBox和WidthBox的制定者。

private double m_distanceBox; 
public double DistanceBox 
{ 
    get { return m_distanceBox; } 
    set 
    { 
     if (m_distanceBox != value) 
     { 
      m_distanceBox = value; 
      NotifyPropertyChanged("DistanceBox"); 
      NotifyPropertyChanged("WidthBased"); 
     } 
    } 
} 

---

的初始值可在您的變量類的構造器或直接在字段聲明，例如被設置

private double m_distanceBox = 10; 
public double DistanceBox //...