访问在MainWindow()构造函数中实例化的类

本文关键字：实例化 构造函数 MainWindow 访问 | 更新日期: 2023-09-27 18:06:41

我是c#和WPF的新手，我在访问MainWindow()构造函数期间实例化的类时遇到了一点麻烦。

下面是我的代码:

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，当选择被改变时，我想从鹪chviewmodel类调用一个函数，它将填充一些变量(我稍后将绑定到TextBlocks)。

然而，我的电话扳手。GetWrench会导致" name扳手在当前上下文中不存在"构建错误。

将鼠标光标移到MainWindow构造函数中的"扳手"实例上，表明它是一个局部变量。

我怎样才能使至少 MainWindow类可以访问它?

访问在MainWindow()构造函数中实例化的类

您可以将变量声明向上移动一个作用域到类中，这样它不仅在构造函数(局部作用域)中可用，而且在整个类中可用:

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);
    }
}

c#中的花括号表示作用域，它告诉您方法、类、命名空间或其他作用域在哪里结束。您不能访问其自身作用域之外的任何内容，也不能从另一个作用域访问。

你需要做的是将变量的声明移到构造函数的作用域之外。您仍然在构造函数中为视图模型赋值，但是声明位于其他方法可以看到的范围内。

一样:

public partial class MainWindow : Window
{
    WrenchViewModel wrench;
    public MainWindow()
    {
        InitializeComponent();
        wrench = new WrenchViewModel();

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。你应该把它改成这个私有成员:

 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);
    }
}
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