c# - 如何将不同的查询结果绑定(bind)到组合框并将其作为选定的单元格值传递

Question

我已经尝试了很多 Stack Overflow 的答案，但我就是找不到一个简单的例子来说明我希望实现的目标。

我试图用来自表 (dimDate) 的不同结果填充组合框，并在选择网格行(来自安全表)时更改该组合框选择。

不用说，我一直在尝试的东西并没有按预期工作。我做错了什么，我怎样才能用最简单的工作示例解决这个问题？

MainWindow.xaml

<Label Content="Year" Margin="0,0,10,0" Grid.Row="0" Grid.Column="0"/>
<ComboBox x:Name="txtyr" Grid.Row="0" Grid.Column="0"
            Width="115" SelectedIndex="0" DisplayMemberPath="Year"
            ItemsSource="{Binding Years}" 
            SelectedValue="{Binding Path=years_SelectedValue}" 
            SelectedValuePath="value">
</ComboBox>

<Label Content="Quarter" Margin="0,0,10,0" Grid.Row="0" Grid.Column="1"/>
<ComboBox x:Name="txtqt" Grid.Row="0" Grid.Column="1"
            Width="115" SelectedIndex="0" DisplayMemberPath="Year"
            ItemsSource="{Binding Quarters}" 
            SelectedValue="{Binding Path=quarters_SelectedValue}" 
            SelectedValuePath="value"/>

<Label Content="Name" Margin="0,0,10,0" Grid.Row="0" Grid.Column="2"/>
<ComboBox x:Name="txtnm" Grid.Row="0"  Grid.Column="2"
            Width="115" SelectedIndex="0" DisplayMemberPath="Year"
            ItemsSource="{Binding Names}" 
            SelectedValue="{Binding Path=names_SelectedValue}" 
            SelectedValuePath="value"/>

<Label Content="Safery Score:" Margin="0,0,10,0" Grid.Row="1" Grid.Column="0"/>
<Controls:NumericUpDown x:Name="txtssc"  Grid.Row="2" Grid.Column="0"
                        Controls:TextBoxHelper.HasText="True" Width="115" Height="20" 
                        Controls:TextBoxHelper.Watermark="Score"
                        UpDownButtonsWidth="25" Maximum="10" Minimum="-10" HasDecimals="False" 
                        InterceptArrowKeys="True" InterceptMouseWheel="True"                         
                        />

<DataGrid Grid.Row="1" Margin="10,10,0,0" AutoGenerateColumns="False" VirtualizingPanel.IsVirtualizingWhenGrouping="True" EnableColumnVirtualization="True" EnableRowVirtualization="True" VirtualizingPanel.IsVirtualizing="true" ColumnHeaderStyle="{StaticResource lowCase}" x:Name="dtGrid" HorizontalAlignment="Left" CanUserResizeRows="False" ItemsSource="{Binding}" GridLinesVisibility="All" HorizontalContentAlignment="Stretch" CanUserAddRows="false" SelectedCellsChanged="dtGrid_SelectedCellsChanged" VerticalAlignment="Top" Grid.ColumnSpan="2" DataContext="{Binding Mode=OneWay, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MainWindow}}}" IsReadOnly="True">
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding Year}" Header="Year"/>
        <DataGridTextColumn Binding="{Binding Quarter}" Header="Quarter"/>
        <DataGridTextColumn Binding="{Binding Name}" Header="Name"/>
        <DataGridTextColumn Binding="{Binding SafetyScore}" Header="Safety Score"/>
        <DataGridTextColumn Binding="{Binding ID}" Header="ID" Visibility="Collapsed"/>
    </DataGrid.Columns>
</DataGrid>

MainWindow.cs

namespace Safety
{
    public partial class MainWindow : MetroWindow
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = new SafetyViewModel();
            string connectionString = "data Source=xxx; initial catalog=xxx; user id=xxx; password=xxx";
            SqlConnection connection = new SqlConnection(connectionString);
            SqlCommand cmd = new SqlCommand("Select ID, Year, Quarter, Name, SaferyScore from MATRIX.dbo.Safety", connection);

            try
            {
                connection.Open();
                DataTable dt = new DataTable();
                dt.Load(cmd.ExecuteReader());
                dtGrid.DataContext = dt;
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            connection.Close();
        }

        private void dtGrid_SelectedCellsChanged(object sender, SelectedCellsChangedEventArgs e)
        {
            DataRowView row_selected = dtGrid.SelectedItem as DataRowView;
            if (row_selected == null) return;
            txtyr.ItemsSource = row_selected["Year"].ToString();
            txtqt.Text = row_selected["Quarter"].ToString();
            txtnm.Text = row_selected["Name"].ToString();
            txtscc.Value = Convert.ToInt16(row_selected["SafetyScore"].ToString());
            txtID.Text = row_selected["ID"].ToString();
        }
    }
}

SafetyViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Safety.Model;
using System.Windows;
using Safety;
using System.Collections.ObjectModel;

namespace Safety.ViewModel
{
    public class SafetyViewModel : INotifyPropertyChanged
    {
        public SafetyViewModel()
        {
            this.loadyearlist();
            this.loadnamelist();
            this.loadquarterslist();
        }

        public void loadyearlist()
        {
            using (MATRIXEntities db = new MATRIXEntities())
            {
                var yrs = (from a in db.dimDate
                         select a).Distinct()
                         .ToList();

                Years = new ObservableCollection<dimDate>(yrs);
            }
        }

        public void loadquarterslist()
        {
            using (MATRIXEntities db = new MATRIXEntities())
            {
                var qts = (from a in db.dimDate
                           select a).Distinct()
                         .ToList();

                Quarters = new ObservableCollection<dimDate>(qts);
            }
        }

        public void loadnamelist()
        {
            using (MATRIXEntities db = new MATRIXEntities())
            {
                var nms = (from a in db.Employees
                         select a)
                         .ToList();

                Employees = new ObservableCollection<Employees>(nms);
            }
        }



        private ObservableCollection<dimDate> years;
        public ObservableCollection<dimDate> Years
        {
            get { return years; }
            set
            {
                years = value;
                OnPropertyChanged("Years");
            }
        }

        public string _years_SelectedValue;
        private string years_SelectedValue
        {
            get { return _years_SelectedValue; }
            set
            {
                _years_SelectedValue = value;
                OnPropertyChanged("years_SelectedValue");
            }
        }

        private ObservableCollection<dimDate> quarters;
        public ObservableCollection<dimDate> Quarters
        {
            get { return quarters; }
            set
            {
                quarters = value;
                OnPropertyChanged("Quarters");
            }
        }

        public string _quarters_SelectedValue;
        private string quarters_SelectedValue
        {
            get { return _quarters_SelectedValue; }
            set
            {
                _quarters_SelectedValue = value;
                OnPropertyChanged("quarters_SelectedValue");
            }
        }

        private ObservableCollection<Employees> employees;
        public ObservableCollection<Employees> Employees
        {
            get { return employees; }
            set
            {
                employees = value;
                OnPropertyChanged("Employees");
            }
        }

        public string _names_SelectedValue;
        private string names_SelectedValue
        {
            get { return _names_SelectedValue; }
            set
            {
                _names_SelectedValue = value;
                OnPropertyChanged("names_SelectedValue");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = null)
            => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    }
}

型号

namespace Safety.Model
{
    using System;
    using System.Collections.Generic;

    public partial class dimDate
    {
        public int DateID { get; set; }
        public System.DateTime Date { get; set; }
        public int Year { get; set; }
        public int Month { get; set; }
        public int Day { get; set; }
        public int Quarter { get; set; }
    }
}

namespace Safety.Model
{
    using System;
    using System.Collections.Generic;

    public partial class Safety
    {
        public int ID { get; set; }
        public int Year { get; set; }
        public int Quarter { get; set; }
        public string Name { get; set; }
        public int SafetyScore { get; set; }
    }
}

namespace Safety.Model
{
    using System;
    using System.Collections.Generic;

    public partial class Employees
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Position { get; set; }
    }
}

Answer 1

你的代码有很多问题。下面列出了一些:

• 绑定(bind)属性应该是公开的而不是私有(private)的
• 在 Code behind 中，您试图设置 ComboBox 的 Text 而不是 SelectedValue
• 您正在将代码隐藏与 ViewModel 设计混合

我编写了下面的代码来演示使用 MVVM 设计模式的要求。

MainWindow.xaml

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.DataContext>
        <local:MainWindowViewModel />
    </Window.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Grid Grid.Row="0">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>
            <StackPanel Margin="5" Grid.Column="0">
                <Label Content="Year" />
                <ComboBox x:Name="txtyr"
                    ItemsSource="{Binding Years}" 
                    SelectedValue="{Binding Path=years_SelectedValue}" />
            </StackPanel>
            <StackPanel Margin="5"  Grid.Column="1">
                <Label Content="Quarter"/>
                <ComboBox x:Name="txtqt"
                ItemsSource="{Binding Quarters}" 
                SelectedValue="{Binding Path=quarters_SelectedValue}" />
            </StackPanel>
            <StackPanel Margin="5"  Grid.Column="2">
                <Label Content="Name" />
                <ComboBox x:Name="txtnm"
                    ItemsSource="{Binding Names}" 
                    SelectedValue="{Binding Path=names_SelectedValue}" />
            </StackPanel>
        </Grid>
        <DataGrid Grid.Row="1" x:Name="dtGrid" ItemsSource="{Binding Safeties}" SelectedItem="{Binding SelectedSafety}">
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding Year}" Header="Year"/>
                <DataGridTextColumn Binding="{Binding Quarter}" Header="Quarter"/>
                <DataGridTextColumn Binding="{Binding Name}" Header="Name"/>
                <DataGridTextColumn Binding="{Binding SafetyScore}" Header="Safety Score"/>
                <DataGridTextColumn Binding="{Binding ID}" Header="ID" Visibility="Collapsed"/>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

为了演示，我在 View 中定义了 ViewModel。

MainViewModel.Cs

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;

namespace WpfApp1
{
    public class MainWindowViewModel : INotifyPropertyChanged
    {
        public MainWindowViewModel()
        {
            var data = Model.GetData();
            Safeties.AddRange(data);
            Years.AddRange(data.Select(d => d.Year).Distinct());
            Quarters.AddRange(data.Select(d => d.Quarter).Distinct());
            Names.AddRange(data.Select(d => d.Name).Distinct());
        }

        private ObservableCollection<int> years = new ObservableCollection<int>();
        public ObservableCollection<int> Years
        {
            get { return years; }
        }

        private int _years_SelectedValue;
        public int years_SelectedValue
        {
            get { return _years_SelectedValue; }
            set
            {
                _years_SelectedValue = value;
                OnPropertyChanged("years_SelectedValue");
            }
        }

        private ObservableCollection<int> quarters = new ObservableCollection<int>();
        public ObservableCollection<int> Quarters
        {
            get { return quarters; }
        }

        private int _quarters_SelectedValue;
        public int quarters_SelectedValue
        {
            get { return _quarters_SelectedValue; }
            set
            {
                _quarters_SelectedValue = value;
                OnPropertyChanged("quarters_SelectedValue");
            }
        }

        private ObservableCollection<string> names = new ObservableCollection<string>();
        public ObservableCollection<string> Names
        {
            get { return names; }
        }

        private string _names_SelectedValue;
        public string names_SelectedValue
        {
            get { return _names_SelectedValue; }
            set
            {
                _names_SelectedValue = value;
                OnPropertyChanged("names_SelectedValue");
            }
        }

        private ObservableCollection<Safety> safeties = new ObservableCollection<Safety>();
        public ObservableCollection<Safety> Safeties
        {
            get { return safeties; }
        }

        private Safety selectedSafety;
        public Safety SelectedSafety
        {
            get { return selectedSafety; }
            set
            {
                selectedSafety = value;
                this.OnPropertyChanged(nameof(SelectedSafety));
                if (this.selectedSafety != null)
                {
                    this.years_SelectedValue = selectedSafety.Year;
                    this.quarters_SelectedValue = selectedSafety.Quarter;
                    this.names_SelectedValue = selectedSafety.Name;
                }
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

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

通过上面的代码合并，下面的 gif 演示了该功能的工作原理:

附加代码

为了演示，我创建了一个类来获取数据

public static class Model
    {
        public static List<Safety> GetData()
        {
            return new List<Safety>()
            {
                new Safety() { ID = 1, Name = "First", Quarter = 1, SafetyScore = 1, Year = 2001 },
                new Safety() { ID = 2, Name = "Second", Quarter = 2, SafetyScore = 1, Year = 2001 },
                new Safety() { ID = 3, Name = "Third", Quarter = 3, SafetyScore = 1, Year = 2001 },
                new Safety() { ID = 4, Name = "Fourth", Quarter = 4, SafetyScore = 1, Year = 2001 },
                new Safety() { ID = 5, Name = "First", Quarter = 1, SafetyScore = 1, Year = 2002 },
                new Safety() { ID = 6, Name = "Second", Quarter = 2, SafetyScore = 1, Year = 2002 },
                new Safety() { ID = 7, Name = "Third", Quarter = 3, SafetyScore = 1, Year = 2002 },
                new Safety() { ID = 8, Name = "Fourth", Quarter = 4, SafetyScore = 1, Year = 2002 },
            };
        }
    }

ObservableCollection 的 AddRange 扩展。但是，您可以使用 C#7.0 中引入的 ObservableRangeCollection

public static class ObservableCollectionExtensions
    { 
        public static void AddRange<T>(this ObservableCollection<T> observableCollection, IEnumerable<T> data)
        {
            foreach (T item in data)
            {
                observableCollection.Add(item);
            }
        }
    }

安全.cs

public class Safety : INotifyPropertyChanged
    {
        private int id;
        public int ID
        {
            get
            {
                return id;
            }
            set
            {
                id = value;
                this.RaisePropertyChange(nameof(ID));
            }
        }

        private int year;
        public int Year
        {
            get
            {
                return year;
            }
            set
            {
                year = value;
                this.RaisePropertyChange(nameof(ID));
            }
        }

        private int quarter;
        public int Quarter
        {
            get
            {
                return quarter;
            }
            set
            {
                quarter = value;
                this.RaisePropertyChange(nameof(ID));
            }
        }

        private string name;
        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
                this.RaisePropertyChange(nameof(ID));
            }
        }

        private int safetyScore;

        public int SafetyScore
        {
            get
            {
                return safetyScore;
            }
            set
            {
                safetyScore = value;
                this.RaisePropertyChange(nameof(ID));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

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