Datagrid错误 - 无法填充Viemodel属性

问题描述

我有一个包含四列的数据网格：

Datagrid通过可观察的集合填充。查看模型是：

  public class PlanningResult：INotifyPropertyChanged 
 {
 public event PropertyChangedEventHandler PropertyChanged; 
 private void NotifyPropertyChanged（[CallerMemberName] String propertyName =）
 {
 if（PropertyChanged！= null）
 PropertyChanged（this，new PropertyChangedEventArgs（propertyName））; 
} 
 public double A {get;组; } 
 public double B {get;组; } 
 public double C {get;组; } 
 public double D {get;组; } 
} 
 
 ObservableCollection< PlanningResult> populatePatternData = new ObservableCollection< PlanningResult>（）; 
 public ObservableCollection< PlanningResult> PopulatePatternData 
 {
 get {return populatePatternData; } 
 set 
 {
 populatePatternData = value; 
 base.OnPropertyChanged（StringList）; 
} 
} 
  

这是我的要求：
- 列C 和列D 应该具有相同的值，除非用户在列A中进行更改或列B 。在这种情况下，列D 应该成为 ColumnA + ColumnB 。

根据上述条件，我可以在视图模型中进行更改为

  public class PlanningResult：INotifyPropertyChanged 
 {
 public event PropertyChangedEventHandler PropertyChanged; 
 private void NotifyPropertyChanged（[CallerMemberName] String propertyName =）
 {
 if（PropertyChanged！= null）
 PropertyChanged（this，new PropertyChangedEventArgs（propertyName））; 
} 
 
 private double _a; 
 public double A 
 {
 get {return _a; } 
 set {_a = value; NotifyPropertyChanged（）; NotifyPropertyChanged（D）; } 
} 
 
 private double _b; 
 public double B 
 {
 get {return _b; } 
 set {_b = value; NotifyPropertyChanged（）; NotifyPropertyChanged（D）; } 
} 
 
 public double D {get {return _a + _b; }} 
 
 public double C {get; set;} 
} 
  

• 我遇到的问题是我无法使用 initial values = values same to columnC 填充columnD。如何向列D提供初始值？




• 当我尝试通过集合来做，我得到一个错误：

属性D不能分配给它 - 只读

解决方案

将一个setter添加到 D 属性中，并将其值设置为 A 和 B 属性：

  public class PlanningResult：INotifyPropertyChanged 
 {
 public event PropertyChangedEventHandler PropertyChanged; 
 private void NotifyPropertyChanged（[CallerMemberName] String propertyName =）
 {
 if（PropertyChanged！= null）
 PropertyChanged（this，new PropertyChangedEventArgs（propertyName））; 
} 
 
 private double _a; 
 public double A 
 {
 get {return _a; } 
 set {_a = value; NotifyPropertyChanged（）; D = _a + _b; } 
} 
 
 private double _b; 
 public double B 
 {
 get {return _b; } 
 set {_b = value; NotifyPropertyChanged（）; D = _a + _b; } 
} 
 
 private double _d; 
 public double D 
 {
 get {return _d; } 
 set {_d = value; NotifyPropertyChanged（）; } 
} 
 
 public double C {get;组; } 
} 
  

I have a datagrid with four columns:

Datagrid is populated via an observable collection. View model is:

public class PlanningResult : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
    public double A { get; set; }
    public double B { get; set; }
    public double C { get; set; }
    public double D { get; set; }
}

ObservableCollection<PlanningResult> populatePatternData = new ObservableCollection<PlanningResult>();
public ObservableCollection<PlanningResult> PopulatePatternData
{
    get { return populatePatternData; }
    set
    {
        populatePatternData = value;
        base.OnPropertyChanged("StringList");
    }
}

Here is the requirement for me:- Column C and Column D should have same values unless user makes a change in Column A or Column B . In that case, Column D should become ColumnA+ColumnB.

Based on the above condition, I can make changes in the view model as

public class PlanningResult : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    private double _a;
    public double A
    {
        get { return _a; }
        set { _a = value; NotifyPropertyChanged(); NotifyPropertyChanged("D"); }
    }

    private double _b;
    public double B
    {
        get { return _b; }
        set { _b = value; NotifyPropertyChanged(); NotifyPropertyChanged("D"); }
    }

    public double D { get { return _a + _b; } }

public double C {get;set;}
    }

• The issue that I face is that I am unable to populate columnD with "initial values = values same as columnC". How do I provide initial values to the column D?

• When I try to do it via collection, I get an error as :

property D cannot be assigned to -- it is read only

解决方案

Add a setter to the D property and set its value in the setter of the A and B properties:

public class PlanningResult : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    private double _a;
    public double A
    {
        get { return _a; }
        set { _a = value; NotifyPropertyChanged(); D = _a + _b; }
    }

    private double _b;
    public double B
    {
        get { return _b; }
        set { _b = value; NotifyPropertyChanged(); D = _a + _b; }
    }

    private double _d;
    public double D
    {
        get { return _d; }
        set { _d = value; NotifyPropertyChanged(); }
    }

    public double C { get; set; }
}

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