Question

我是C＃和WPF的新手，我在访问在MainWindow（）构造函数中实例化的类时遇到了一些麻烦。

这是我的代码：

namespace PivotBlockPicker.View
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            WrenchViewModel wrench = new WrenchViewModel();
            MeasurementViewModel measurements = new MeasurementViewModel();
        }

        private void modelSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            wrench.GetWrench(modelSelector.SelectedItem);
        }
    }
}

这是我的XAML：

<Window x:Class="PivotBlockPicker.View.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:PivotBlockPicker.View"
        xmlns:vm="clr-namespace:PivotBlockPicker.ViewModel"
        xmlns:m="clr-namespace:PivotBlockPicker.Model"
        mc:Ignorable="d"
        Title="MainWindow" Height="347" Width="288.666"
        DataContext="vm:WrenchViewModel">
    <Grid>
        <GroupBox x:Name="wrenchBox" Header="Torque Wrench" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top" Height="262" Width="250">
            <Grid>
                <Grid Margin="0,0,0,140.667" Height="88" VerticalAlignment="Bottom">
                    <TextBlock x:Name="textBlock" HorizontalAlignment="Left" Margin="10,3,0,0" TextWrapping="Wrap" Text="Model:" VerticalAlignment="Top"/>
                    <ComboBox x:Name="modelSelector" HorizontalAlignment="Left" Margin="52,0,0,0" VerticalAlignment="Top" Width="120" SelectionChanged="modelSelector_SelectionChanged">
                        <ComboBoxItem>QD2R200</ComboBoxItem>
                        <ComboBoxItem>QD2R50</ComboBoxItem>
                    </ComboBox>
                    <Grid HorizontalAlignment="Left" Width="228" Margin="0,27,0,0">
                        <TextBlock x:Name="blockFirstTP" Text="TextBlock" HorizontalAlignment="Left" Margin="10,0,0,0" TextWrapping="Wrap" VerticalAlignment="Top"/>
                        <TextBlock x:Name="blockSecondTP" Text="TextBlock" HorizontalAlignment="Left" Margin="10,21,0,0" TextWrapping="Wrap" VerticalAlignment="Top"/>
                        <TextBlock x:Name="blockThirdTP" Text="TextBlock" HorizontalAlignment="Left" Margin="10,42,0,0" TextWrapping="Wrap" VerticalAlignment="Top"/>
                    </Grid>
                </Grid>
                <GroupBox x:Name="blockBox" Header="Pivot Block Dimensions" HorizontalAlignment="Left" Margin="10,100,0,0" VerticalAlignment="Top" Height="86">
                    <Grid>
                        <TextBlock x:Name="blockTextHorizontal" HorizontalAlignment="Left" Margin="51,12,0,0" TextWrapping="Wrap" Text="Vertical" VerticalAlignment="Top" Height="16" Width="40"/>
                        <TextBox x:Name="blockHorizontal" Text="" HorizontalAlignment="Left" Height="20" Margin="10,10,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="36" MaxLength="5"/>
                        <TextBlock x:Name="blockTextVertical" HorizontalAlignment="Left" Margin="51,37,0,0" TextWrapping="Wrap" Text="Horizontal" VerticalAlignment="Top" Height="16" Width="58"/>
                        <TextBox x:Name="blockVertical" Text=""  HorizontalAlignment="Left" Height="20" Margin="10,35,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="36" MaxLength="5"/>
                    </Grid>
                </GroupBox>
            </Grid>
        </GroupBox>
        <Button x:Name="button" Content="Get Wrench Info" HorizontalAlignment="Left" Margin="185,277,0,0" VerticalAlignment="Top" Width="75"/>
    </Grid>
</Window>

我的窗口有一个ComboBox，当选择被更改时，我想从WrenchViewModel类调用一个函数来填充一些变量（我稍后将数据绑定到TextBlocks。

但是，我对wrench.GetWrench的调用会导致“当前上下文中不存在名称扳手”构建错误。

将我的鼠标光标悬停在MainWindow构造函数中的“wrench”实例上，表明它是一个局部变量。

我怎样才能让至少使用MainWindow类？

Answer 1

您可以将变量声明一个范围移到类中，因此它不仅可以在构造函数（本地范围）中使用，而且可以在整个类中使用：

public partial class MainWindow : Window
{
    private WrenchViewModel wrench;
    private MeasurementViewModel measurements;

    public MainWindow()
    {
        InitializeComponent();

        wrench = new WrenchViewModel();
        measurements = new MeasurementViewModel();
    }

    private void modelSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        wrench.GetWrench(modelSelector.SelectedItem);
    }
}

Answer 2

C＃中的花括号括号表示范围，告诉您方法，类，命名空间或其他范围的结束位置。您无法访问其自身范围之外的任何内容，也无法访问其他范围内的任何内容。

您需要做的是将变量的声明移到构造函数的范围之外。您仍然在构造函数的一侧分配视图模型，但声明在另一个方法可以看到的范围内。

像这样：

public partial class MainWindow : Window
{
    WrenchViewModel wrench;

    public MainWindow()
    {
        InitializeComponent();
        wrench = new WrenchViewModel();

Answer 3

因为您已经定义了一个局部变量：

 public MainWindow()
    {
        InitializeComponent();
        WrenchViewModel wrench = new WrenchViewModel();
        MeasurementViewModel measurements = new MeasurementViewModel();
    }

构造函数内部。您应该将其更改为此私人成员：

 public partial class MainWindow : Window
 {


private WrenchViewModel _wrench = new WrenchViewModel();
 private  MeasurementViewModel _measurements = new MeasurementViewModel();
    public MainWindow()
    {
        InitializeComponent();
    }

    private void modelSelector_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        _wrench.GetWrench(modelSelector.SelectedItem);
    }
}

访问在MainWindow（）构造函数

3 个答案: