.NET MAUI数据绑定和MVVM

Question

这似乎很简单，但我无法让它正常工作。最简单的MAUI应用程序，标签绑定到“CountDisplay”，按钮绑定到“IncreaseCount”。命令绑定起作用，标签绑定第一次读取其值，但从未刷新。我做错了什么？谢谢你的帮助。

MainPage.xaml

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="MauiApp1.MainPage"
         BackgroundColor="{DynamicResource SecondaryColor}">

<ScrollView>
    <Grid RowSpacing="25" RowDefinitions="Auto,Auto,Auto,Auto,*"
          Padding="{OnPlatform iOS='30,60,30,30', Default='30'}">

         <Label 
            Text="{Binding CountDisplay}"
            Grid.Row="2"
            FontSize="18"
            FontAttributes="Bold"
            HorizontalOptions="Center" 
            />

        <Button 
            Text="Click me"
            FontAttributes="Bold"
            Grid.Row="3"
            SemanticProperties.Hint="Counts the number of times you click"
            Command="{Binding IncreaseCount}"
            HorizontalOptions="Center" />

    </Grid>
    
    
</ScrollView>

MainPageViewModel。反恐精英

public class MainPageViewModel:BindableObject   
{
    public MainPageViewModel()
    {
        IncreaseCount = new Command(OnIncrease);
    }
    public ICommand IncreaseCount { get; }

    int count = 0;
    string countDisplay = "Click Me()!";

    public string CountDisplay
    {
        get { return countDisplay; }

        set
        {
            if (value == countDisplay)
                return;

            countDisplay = value;
            OnPropertyChanged();
            
        }
    }

    void OnIncrease()
    {
        count++;
        countDisplay = $"Current count: {count}";
    }
}

Answer 1

您正在设置私有变量（小写字母“c”）

void OnIncrease()
{
    count++;
    countDisplay = $"Current count: {count}";
}

相反，您需要设置public属性（大写字母"C"），否则不调用OnProperty tyChanged

void OnIncrease()
{
    count++;
    CountDisplay = $"Current count: {count}";
}

一种流行的惯例是用命名私有变量，这样两个名称就更难混淆（countDisplay和countDisplay）