数据绑定到计算字段

Question

我遇到了一个小问题，我试图将 DataGrid 的 DataTextColumn 绑定到计算字段。

WPF

<DataGrid ItemsSource="{Binding Path=CurrentRoster, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
          AutoGenerateColumns="False" 
          AlternatingRowBackground="Gainsboro"  
          AlternationCount="2">
    <DataGrid.Columns>
    <DataGridComboBoxColumn Header="Student Enrolled"
                            ItemsSource="{Binding Source={StaticResource AvailableStudents}}"
                            SelectedItemBinding="{Binding Path=Student}">
    </DataGridComboBoxColumn>
    <DataGridTextColumn Header="Registration" Binding="{Binding Path=RegistrationCosts, StringFormat='{}{0:C}'}"/>
    <DataGridTextColumn Header="Lodging" Binding="{Binding Path=LodgingCosts, StringFormat='{}{0:C}'}"/>
    <DataGridTextColumn Header="Travel" Binding="{Binding Path=TravelCosts, StringFormat='{}{0:C}'}"/>
    <DataGridTextColumn Header="Dining" Binding="{Binding Path=DiningCosts, StringFormat='{}{0:C}'}"/>
    <DataGridTextColumn Header="Total Costs" IsReadOnly="True" Binding="{Binding Path=TotalCosts, StringFormat='{}{0:C}'}"/>
</DataGrid.Columns>

Student 是一个 Entity 对象，有一个小的添加。 TotalCosts 不是 db 表上的字段，因此我为此创建了一个部分类。

public partial class Student
{
    public  Decimal TotalCosts
    {
        get { return (LodgingCosts + RegistrationCosts + TravelCosts + DiningCosts); }
    }
}

我遇到的问题是，当您填写任何其他字段时，TotalCosts 不会自动更新。我的猜测是因为它没有被列为依赖属性。对于没有设置的属性，我该如何解决这个问题？

Answer 1

我假设 Student 实现了 INotifyPropertyChanged。您需要做的是注册到 LodgingCosts + RegistrationCosts + TravelCosts + DiningCosts 的 PropertyChanged 事件，并为 TotalCosts 引发 PropertyChanged 事件。

public partial class Student
{
    public Decimal TotalCosts
    {
        get { return (LodgingCosts + RegistrationCosts + TravelCosts + DiningCosts); }
    }

    public Student()
    {
        this.PropertyChanged += new PropertyChangedEventHandler(Student_PropertyChanged);
    }

    void Student_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == "LodgingCosts" ||
            e.PropertyName == "RegistrationCosts" ||
            e.PropertyName == "TravelCosts" ||
            e.PropertyName == "DiningCosts")
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs("TotalCosts"));
        }
    }

}

Answer 2

你可以在TotalCosts所依赖的每个属性的setter中调用OnPropertyChanged("TotalCosts")，它会刷新绑定

Answer 3

您好，我想我可以帮助您，我有此代码用于 sqlServer 中的数据库 我有一个数据源和我的数据库的数据集

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 TestDeDataGrid.TestDSTableAdapters;

namespace TestDeDataGrid
{

    public partial class MainWindow : Window
    {
        //private ICollection<TablaTest> registros;

        public MainWindow()
        {
            InitializeComponent();

            TestDS ds = new TestDS();
            TablaTestTableAdapter adapter = new TablaTestTableAdapter();
            adapter.Fill(ds.TablaTest);


            TablaTestGrid.ItemsSource = ds.TablaTest.DefaultView;
        }


        private void TablaTestGrid_CurrentCellChanged(object sender, EventArgs e)
        {
            if ((String)(((DataGrid)sender).CurrentColumn.Header) == "A/B")
                ((DataGrid)sender).CommitEdit(DataGridEditingUnit.Row, true);
        }
    }
}

有了这个技巧，在我有一个值之后，C列就会自动计算出来 例如，在 A 列和 B 列中，如果我在 A 列中放入 10，在 B 列中放入 5 然后我只需按 Tab 键移动到 columnC 并且值 2 会自动出现 无需点击其他行或回车。

ColumnC 是一个计算列，其表达式为 (ColumnaA/ColumnaB)，类型为 System.Decimal。

还有我的 xaml 代码：

<DataGrid Name="TablaTestGrid" Grid.Row="1" AutoGenerateColumns="False"                    
              CurrentCellChanged="TablaTestGrid_CurrentCellChanged">
        <DataGrid.Columns>
            <DataGridTextColumn Header="ID" Binding="{Binding Path=IdTablaTest}" IsReadOnly="True"></DataGridTextColumn>
            <DataGridTextColumn Header="Col A" Binding="{Binding Path=ColumnaA}"></DataGridTextColumn>
            <DataGridTextColumn Header="Col B" Binding="{Binding Path=ColumnaB}"></DataGridTextColumn>
            <DataGridTextColumn Header="A/B" Binding="{Binding Path=ColumnaC}" IsReadOnly="True" ></DataGridTextColumn>               
            <DataGridTextColumn Header="TestOnly"></DataGridTextColumn>
        </DataGrid.Columns>
    </DataGrid>

Answer 4

只需将DataBinding 创建为TotalCosts 属性时，将DataSourceUpdateMode 更改为OnPropertyChanged。

Answer 5

你需要在类上实现INotifyPropertyChanged。这是示例：

public class Person : INotifyPropertyChanged
{
    //public int Id
    //{ get; set; }

    //public string Name { get; set; }

    private int _Id;

    public int Id
    {
        get { return _Id; }
        set { _Id = value;
        RaisePropertyChanged("Id");
        }
    }

    private string _EmpNo
    {
        get
        {
            return Id.ToString() + Name.ToString();
        }
    }

    private string _Name;

    public string Name
    {
        get { return _Name; }
        set
        {
            _Name = value;
            RaisePropertyChanged("Name");
        }
    }

    private void RaisePropertyChanged(string property)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(property));
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

XAML 代码：

<DockPanel>
    <TextBox Text="{Binding P1.Id}" Height="50" Width="100" DockPanel.Dock="Top" />
    <TextBox Text="{Binding P1.Name}" Height="50" Width="100" DockPanel.Dock="Top" />
    <Button Content="OK" Click="Button_Click" DockPanel.Dock="Bottom"/>
</DockPanel>

测试：

public TestWindow()
{
    InitializeComponent();

    this.DataContext = this;
}

private Person _P1 = new Person();

public Person P1
{
    get { return _P1; }
    set { _P1 = value; }
}

private void Button_Click(object sender, RoutedEventArgs e)
{

}

在 2 个文本框中输入内容..然后在按钮上单击查看人 P1 的值 ..u 将找到具有该值的计算字段.. 希望它可以帮助你.. 谢谢， 哈维克