无法通过命令将值从视图传递到视图模型

Question

我正在为我的应用程序实现 MVVM 模式。我有我的视图、视图模型、模型和命令和转换器正在实施。现在我无法通过命令绑定将我的文本框值从我的数据模板传递给我的 ViewModel。我可以单击按钮尝试更新过程，但它无法传递文本框值。我的命令类有什么需要更改的吗？

这是我的 XAML：

<DataGrid AutoGenerateColumns="False" Grid.Row="2" Grid.ColumnSpan="4" Grid.RowSpan="3" x:Name="productionLineConfigDataGrid" Margin="70,0.2,70,0" ItemsSource="{Binding listAllProductionLineConfigs}">
<DataTemplate>
<StackPanel>
        <StackPanel Orientation="Horizontal">
                <TextBlock FontSize="12" Text="ID: " VerticalAlignment="Center" />
                <TextBlock x:Name="txtBlockLineId" FontSize="16" Foreground="MidnightBlue" Text="{Binding ProductionLineId, Mode=TwoWay}" VerticalAlignment="Center" />
        </StackPanel>
        <StackPanel>
                <Button x:Name="btnUpdate" Content="Update" VerticalAlignment="Center" HorizontalAlignment="Right" Click="btnUpdate_Click" Command="{Binding DataContext.updateProductionLineConfigCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:production_line_config_home}}}" CommandParameter="{Binding ProductionLineConfig}"/>
        </StackPanel>
</StackPanel>
</DataTemplate>
</DataGrid>

这是我的 ViewModel 中的方法：

public ProductionLineConfig ProductionLineConfig
    {
        get { return productionlineconfig; }

        set
        {
            productionlineconfig = value;
            OnPropertyChanged("ProductionLineConfig");
        }
    }

这是我收到的错误消息：

System.Windows.Data 错误：40：BindingExpression 路径错误：在“对象”“ProductionLineConfig”（HashCode=47309994）上找不到“ProductionLineConfig”属性。绑定表达式：路径=生产线配置； DataItem='ProductionLineConfig' (HashCode=47309994);目标元素是 'Button' (Name='');目标属性是'CommandParameter'（类型'Object'）

我已经为我的应用程序添加了图片here

这是整个 xaml 代码 here 这是整个视图模型代码 here

Answer 1

我只是猜测一下。

假设ProductionLineConfig 是您在模板中为ProductionLineId 绑定的内容。那么您可能只是想将绑定源作为命令参数传递

CommandParameter="{Binding}"

当{Binding} 为空时，表示Binding 绑定到任何Source。这也只是...的简写。

{Binding DataContext,RelativeSource={RelativeSource Self}}.

反过来（如果星星对齐），那么它应该是你的ProductionLineConfig

Answer 2

根据您的代码源，我做了一个示例实现，以满足您的要求。

示例虚拟机：

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;

namespace WpfApp5.ViewModels
{
    public class ProductionLineConfigViewModel : INotifyPropertyChanged
    {
        public CustomCommand<ProductionLineConfig> UpdateCommand { get; }

        public ProductionLineConfigViewModel()
        {
            PopulateProductionLineConfigs();
            UpdateCommand = new CustomCommand<ProductionLineConfig>(UpdateConfig, (u) => true);
        }

        private ObservableCollection<ProductionLineConfig> _listAllProductionLineConfigs;
        public ObservableCollection<ProductionLineConfig> listAllProductionLineConfigs
        {
            get { return _listAllProductionLineConfigs; }
            set
            {
                _listAllProductionLineConfigs = value;
                OnPropertyChanged();
            }
        }

        //  Call this from constructor.
        private void PopulateProductionLineConfigs()
        {
            listAllProductionLineConfigs = new ObservableCollection<ProductionLineConfig>
            {
                new ProductionLineConfig
                {
                    ProductionLineId = 1,
                    ProductionLineCode = "001",
                    ProductionLineCreatedDate = DateTime.Today.Date,
                    ProductionLineName = "safdsf",
                    ProductionLineStatus = true
                },
                new ProductionLineConfig
                {
                    ProductionLineId = 1,
                    ProductionLineCode = "002",
                    ProductionLineCreatedDate = DateTime.Today.Date,
                    ProductionLineName = "sadfadfsdf",
                    ProductionLineStatus = true
                }
            };
        }

        private void UpdateConfig(ProductionLineConfig config)
        {
            MessageBox.Show("Line Name update: " + config.ProductionLineName);
        }

        public event PropertyChangedEventHandler PropertyChanged;

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

    }

    public class ProductionLineConfig
    { 
        public int ProductionLineId { get; set; }

        public string ProductionLineCode { get; set; }

        public string ProductionLineName { get; set; }

        public bool ProductionLineStatus { get; set; }
        public DateTime ProductionLineCreatedDate { get; set; }
    }
}

XAML 示例：

<Window x:Name="Root" x:Class="WpfApp5.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:viewModels="clr-namespace:WpfApp5.ViewModels"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.DataContext>
        <viewModels:ProductionLineConfigViewModel/>
    </Window.DataContext>

    <Grid Background="#FF006E8C">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Label Grid.ColumnSpan="4" Content="KAD ShopFloor System" HorizontalAlignment="Center" Margin="10" FontWeight="Bold" FontSize="30" FontFamily="Segoe UI" Foreground="White"/>
        <Separator Grid.ColumnSpan="4" Grid.RowSpan="3" Background="White" Margin="0,-35,-0.4,39.2"/>
        <DataGrid AutoGenerateColumns="False" Grid.Row="2" Grid.ColumnSpan="4" Grid.RowSpan="3" x:Name="productionLineConfigDataGrid" Margin="70,0.2,70,0"
                  ItemsSource="{Binding DataContext.listAllProductionLineConfigs, ElementName=Root}">
            <DataGrid.Columns>
                <DataGridTextColumn Header="ID" Binding="{Binding ProductionLineId, Mode=TwoWay}"/>
                <DataGridTextColumn Header="Production Line Code" Binding="{Binding ProductionLineCode, Mode=TwoWay}"/>
                <DataGridTextColumn Header="Production Line Name" Binding="{Binding ProductionLineName, Mode=TwoWay}"/>
                <DataGridTextColumn Header="Status" Binding="{Binding ProductionLineStatus, Mode=TwoWay}"/>
                <DataGridTextColumn Header="Created Date" Binding="{Binding ProductionLineCreatedDate, Mode=TwoWay}"/>
            </DataGrid.Columns>
            <DataGrid.RowDetailsTemplate>
                <DataTemplate>
                    <Border BorderThickness="0" Background="BlanchedAlmond" Padding="10">
                        <StackPanel Orientation="Vertical" x:Name="stck">
                            <StackPanel Orientation="Horizontal">
                                <TextBlock FontSize="12" Text="ID: " VerticalAlignment="Center" />
                                <TextBlock x:Name="txtBlockLineId" FontSize="16" Foreground="MidnightBlue" Text="{Binding ProductionLineId, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Center" />
                            </StackPanel>
                            <StackPanel Orientation="Horizontal">
                                <TextBlock FontSize="12" Text="Line Code: " VerticalAlignment="Center" />
                                <TextBlock x:Name="txtBlockLineCode" FontSize="16" Foreground="MidnightBlue" Text="{Binding ProductionLineCode, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Center" />
                            </StackPanel>
                            <StackPanel Orientation="Horizontal">
                                <TextBlock FontSize="12" Text="Line Name: " VerticalAlignment="Center" />
                                <TextBox x:Name="txtLineName" FontSize="16" Foreground="MidnightBlue" Text="{Binding ProductionLineName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Center" />
                            </StackPanel>
                            <!--<StackPanel Orientation="Horizontal">
                                <TextBlock FontSize="12" Text="Status: " VerticalAlignment="Center" />
                                <ComboBox ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type DataGrid}},
                                    Path=DataContext.Statusstring}" SelectedValue="{Binding ProductionLineStatus, Converter={StaticResource statusToBooleanConverter}, Mode=TwoWay}" x:Name="cbProductionLineStatus" FlowDirection="LeftToRight" FontSize="16" Foreground="MidnightBlue"
                                    HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
                            </StackPanel>-->
                            <StackPanel>
                                <Button x:Name="btnUpdate" Content="Update" VerticalAlignment="Center" HorizontalAlignment="Right"
                                        Command="{Binding DataContext.UpdateCommand, ElementName=Root}"
                                        CommandParameter="{Binding}" />
                            </StackPanel>
                        </StackPanel>
                    </Border>
                </DataTemplate>
            </DataGrid.RowDetailsTemplate>
        </DataGrid>

    </Grid>
</Window>

样本输出：

这里的主要变化，

1. 您需要将列表更改为可观察集合

2. 创建一个接受对象的自定义命令，参见这篇文章：[UWP/MVVM]Enable/Disable Button in RadDataGrid Data Template Column that have commands bound to them upon conditions

3. Command Parameter应该是迭代项，可以通过CommandParameter={Binding}实现

4. 在你的双向绑定中，确保添加UpdateSourceTrigger=PropertyChanged