.NET 6 MAUI自定义控件绑定Title时触发XFC0009错误求助

问题原因 #

你遇到的XFC0009错误，核心原因是可绑定属性的声明不符合MAUI要求：

• MAUI规定，自定义可绑定属性必须声明为public static readonly类型的字段
• 当前的TitleProperty和RunningProperty是普通的public实例字段，XAML编译器无法识别为合法的可绑定属性，因此绑定时报错。直接赋值时调用的是CLR属性（Title/Running），所以不会报错，但数据绑定依赖可绑定属性的静态字段，因此失败。

解决步骤 #

将两个可绑定属性的声明改为public static readonly，具体修改如下：

修改后的后台代码 #

public partial class CustomProgressDialog : VerticalStackLayout
{
    #region CTOR
    public CustomProgressDialog()
    {
        InitializeComponent();
    }
    #endregion

    #region BINDABLE PROPERTY
    // 修改为public static readonly
    public static readonly BindableProperty TitleProperty = BindableProperty.Create(
        propertyName: nameof(Title),
        returnType: typeof(string),
        declaringType: typeof(CustomProgressDialog),
        defaultValue: "Please wait...",
        defaultBindingMode: BindingMode.TwoWay,
        propertyChanged: (bindable, oldvalue, newvalue) =>
        {
            var control = (CustomProgressDialog)bindable;
            control.TitleLabel.Text = newvalue as string;
        });

    // 修改为public static readonly
    public static readonly BindableProperty RunningProperty = BindableProperty.Create(
        propertyName: nameof(Running),
        returnType: typeof(bool),
        declaringType: typeof(CustomProgressDialog),
        defaultValue: false,
        defaultBindingMode: BindingMode.TwoWay,
        propertyChanged: (bindable, oldvalue, newvalue) =>
        {
            var control = (CustomProgressDialog)bindable;
            control.Indicator.IsRunning = (bool)newvalue;
        });
    #endregion

    #region PROPERTY
    public string Title
    {      
        get => (string)GetValue(TitleProperty);
        set => SetValue(TitleProperty, value);
    }

    public bool Running
    {       
        get => (bool)GetValue(RunningProperty);
        set => SetValue(RunningProperty, value);
    }
    #endregion
}

验证说明 #

修改后，XAML编译器能够正确识别Title和Running对应的可绑定属性，数据绑定Running="{Binding IsBusy}"和Title="{Binding Message}"即可正常工作，同时直接赋值的方式也不受影响。

内容的提问来源于stack exchange，提问作者abhi