使用WPF在C＃中动态更改图像

Question

I am having issues of having an image change dynamically.

Some background info: I have a list box that contains elements that can be selected. These items are food categories. When a user clicks on one of the foods, I would like an image at a different location of the page to change.

My Xaml file contains:

<Image Name="bigImage" Stretch="Fill" Grid.Row="0" Grid.Column="0" HorizontalAlignment="Center" VerticalAlignment="Center"/>

So when the user clicks a certain food category that "bigImage" would change:

FoodCollection foods = (FoodCollection)this.FindResource("FoodCategory");
            Food f = foods[foodListBox.SelectedIndex];
            Title_TextBlock.Text = f.Name;
            bigImage = f.MainImage;

In my food class I have a variable called Image m_mainImage:

    public class Food
    {
        ...

        Image m_mainImage = new Image();
        String m_mainImagePath = string.Empty;

        ...

        public string MainImagePath{
            get { return m_mainImagePath; }
            set
            {
                m_mainImagePath = value;
                m_mainImage.BeginInit();
                m_mainImage.Source = new BitmapImage(new Uri(m_mainImagePath, UriKind.RelativeOrAbsolute));
                m_mainImage.EndInit();
                RaisePropertyChanged("MainImage");
                RaisePropertyChanged("MainImagePath");
            }
        }

        public Image MainImage
        {
            get { return m_mainImage; }
        }


        public event PropertyChangedEventHandler PropertyChanged;
        protected void RaisePropertyChanged(string name)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(name));
        }

    }
}

I read somewhere that I had to "resolve" the image, but I was unclear on what that meant. I thought this would do it:

m_mainImage.BeginInit();
                    m_mainImage.Source = new BitmapImage(new Uri(m_mainImagePath, UriKind.RelativeOrAbsolute));
                    m_mainImage.EndInit();

Sorry I am still new to WPF and C#. Thanks in advance.

Answer 1

Setup some TwoWay Binding:

Try:

 bigImage.SetBinding(Image.SourceProperty, new Binding(){
      Source = f,
      Path = new PropertyPath("MainImage"),
      Mode=BindingMode.TwoWay
   });

Or:

<Image Name="bigImage" 
       Stretch="Fill" 
       Grid.Row="0" 
       Grid.Column="0" 
       HorizontalAlignment="Center" 
       VerticalAlignment="Center" 
       Source="{Binding Path=MyBitmapImage, Mode=TwoWay}"/>

public BitmapImage MyBitmapImage
{
   get
   {
      return new BitmapImage(new Uri(m_mainImagePath, UriKind.RelativeOrAbsolute));
   }
}

Answer 2

Have you set the DataContext of the window?

Without this PropertyChanged won't be initialised, so:

if (PropertyChanged != null)
    PropertyChanged(this, new PropertyChangedEventArgs(name));

will never fire as PropertyChanged is always null .

Answer 3

Not sure if this will help, but shouldn't the call to m_mainImage.EndInit() in the setter for MainImagePath occur after the call for RaisePropertyChanged("MainImage") ...

Andrew