Datagrid错误 - 无法填充Viemodel属性

Question

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：

    +---------+--------------+-------------+------------+------------+-----------+
    | bill_no | s_f_2000ml   | s_f_1000ml  | m_w_2000ml | m_w_1000ml | bill_date |
    +---------+------------- + ------------+------------+------------+-----------+
    |  2001   |      2       |     1       |     3      |     4      |01-02-2017 |
    +---------+--------------+-------------+------------+------------+-----------+

这是我的要求： - 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"); } } 和Column C应具有相同的值，除非用户在Column D或Column A中进行了更改。在这种情况下，Column B应该成为Column D。

基于上述条件，我可以在视图模型中进行更改

ColumnA+ColumnB

• 我遇到的问题是我无法使用“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;} } ”填充columnD。如何为列D提供初始值？

• 当我尝试通过收集时，我收到一个错误：

initial values = values same as columnC

Answer 1

在D属性中添加一个setter，并在A和B属性的setter中设置其值：

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; }
}

Answer 2

您可以使用其他字段来存储A或B是否已更改。

private bool hasAorBChanged = false;

A或B更改后，此字段可设为true。

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

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

然后属性D看起来像

public double D { get { return hasAorBChanged ? _a + _b : C; } }

不是最干净的解决方案，但考虑到D是只读的，这应该可行。

修改：您也可以将hasAorBChanged = true;移至方法NotifyPropertyChanged()。它会让它变得更加清洁。