数据绑定到实例方法

Question

我有一个带有本地数据库 (SQL CE) 的应用程序，我想将一个列表框绑定到一个表 (Car)。但是，我无法将 WriteableBitmap 保存到本地数据库，因此我决定将图像转换为字节数组，因此我需要动态调用该方法。这是我到目前为止所得到的。

[Table]
class Car
{
    [Column (IsPrimaryKey=true, IsDbGenerated=true, CanBeNull=false, AutoSync = AutoSync.OnInsert)]
    public int ID { get; set; }

    [Column (CanBeNull=false)]
    public int MakeID { get; set; }

    [Column(CanBeNull = false)]
    public int ModelID { get; set; }

    [Column(CanBeNull = false)]
    public int AccountID { get; set; }

    [Column(CanBeNull = false)]
    public int Year { get; set; }

    [Column]
    public string Name { get; set; }

    [Column]
    public byte[] PicBytes { get; set; }

    private EntitySet<Maintenance> maintenance;
    [Association(Storage = "maintenance", ThisKey = "ID", OtherKey = "CarID")]
    public EntitySet<Maintenance> Maintenance
    {
        set
        {
            maintenance = value;
        }
        get
        {
            if (maintenance == null)
                return new EntitySet<Maintenance>();

            return maintenance;
        }
    }

    public WriteableBitmap GetPicture()
    {
        using (var memoryStream = new MemoryStream(PicBytes))
        {
            return PictureDecoder.DecodeJpeg(memoryStream);
        }
    }
}

这是 XAML：

        <ListBox Name="carList" Grid.RowSpan="2" Width="480" SelectionChanged="carList_SelectionChanged">
            <ListBox.ItemTemplate>
                <DataTemplate>
                            <StackPanel Orientation="Horizontal">
                                <Grid>
                                    <Grid.RowDefinitions>
                                        <RowDefinition Height="*"/>
                                        <RowDefinition Height="*"/>
                                        <RowDefinition Height="*"/>
                                        <RowDefinition Height="*"/>
                                    </Grid.RowDefinitions>
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition Width="205"/>
                                        <ColumnDefinition Width="*"/>
                                    </Grid.ColumnDefinitions>


                                    <Image Grid.RowSpan="4"
                                           Grid.Column="0"
                                           Source="{Binding PicByte}"
                                           Stretch="Uniform"/>


                                    <TextBlock Text="{Binding Name}"
                                               TextWrapping="Wrap"
                                               Grid.Row="0"
                                               Grid.Column="1"
                                               VerticalAlignment="Stretch"
                                               HorizontalAlignment="Center"
                                               Width="160"/>
                                    <TextBlock Text="{Binding MakeID}"
                                               TextWrapping="Wrap"
                                               Grid.Row="1"
                                               Grid.Column="1"
                                               VerticalAlignment="Stretch"
                                               HorizontalAlignment="Center"
                                               Width="160"/>
                                    <TextBlock Text="{Binding ModelID}"
                                               TextWrapping="Wrap"
                                               Grid.Row="2" 
                                               Grid.Column="1"
                                               VerticalAlignment="Stretch"
                                               HorizontalAlignment="Center"
                                               Width="160"/>
                                    <TextBlock Text="{Binding Year}"
                                               TextWrapping="Wrap"
                                               Grid.Row="3"
                                               Grid.Column="1"
                                               VerticalAlignment="Stretch"
                                               HorizontalAlignment="Center"
                                               Width="160"/>
                                </Grid>
                            </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

我的主要问题是图像，如何从 XAML 调用方法 GetPicture()。还是我应该用 C# 来做这一切？

编辑：我找到了解决问题的方法

        try
        {
            var db = MHDatabase.GetDatabase();
            var query = from car in db.Cars
                        join make in db.Makes on car.MakeID equals make.ID
                        join model in db.Model on car.ModelID equals model.ID
                        select new
                        {
                            Name = car.Name,
                            Make = make.Name,
                            Model = model.Name,
                            Picture = car.GetPicture(),
                            Year = car.Year
                        };

            carList.ItemsSource = query;
        }
        catch (Exception)
        {
        }

Answer 1

您不能直接绑定到方法。在您的情况下，我至少看到了两种解决方法：

1. 绑定到PicBytes 并制作一个转换器，将字节数组转换为WriteableBitmap

2. 创建Picture 属性：

   public WriteableBitmap Picture
   {
       get
       {
           using (var memoryStream = new MemoryStream(PicBytes))
           {
               return PictureDecoder.DecodeJpeg(memoryStream);
           }
       }
   }