如何在c＃mvvm中檢查bitmapimage的源路徑是否有效

Question

我試圖獲取圖像運行時並基於ImageFilePathName搜索圖像。 但是有可能圖像不存在但仍然使用空圖像創建源路徑。 如果源中包含有效的文件或圖像，請任何人都可以建議如何檢查。 謝謝

public object Convert(object value, Type targetType, object parameter, string culture)
    {
        StorageFolder installFolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
        string installFolderPath = installFolder.Path;
        const string LOGO_KIND_SMALL = "Small";

        ImageSource source;
        string logoImageFilePathName;

              try
        {
            int logoId = Int32.Parse((string)value);
            logoImageFilePathName = string.Format("{0}\\{1}\\Logos\\Chan\\{2}\\{3:0000}.png", installFolderPath, "Assets", LOGO_KIND_SMALL, logoId);

            try
            {
                source = new BitmapImage(new Uri(logoImageFilePathName));

                return source; 
            }
            catch(Exception ex)
            {
                Logger.LogError(ex.Message);
            }


        }
        catch (Exception ex)
        {
            Logger.LogError(ex.Message);
        }

        logoImageFilePathName = string.Format("{0}\\{1}\\Logos\\Channels\\{2}\\{3}.png", installFolderPath, "Assets", LOGO_KIND_SMALL, "0000");
        source = new BitmapImage(new Uri(logoImageFilePathName));
        return source;


    }

    public object ConvertBack(object value, Type targetType, object parameter, string culture)
    {
        throw new NotSupportedException();
    }

Answer 1

要檢查並查看路徑是否有效，您可以使用File.Exists(path); 。 但只是為了知識，如果你想看看字符串是否是一個路徑或只是文本Uri.IsWellFormedUriString(parameter, UriKind.Absolute)

所以你會用：

public object Convert(object value, Type targetType, object parameter, string culture)
{
    string installFolderPath = System.Windows.ApplicationModel.Package.Current.InstalledLocation.Path;
    const string LOGO_KIND_SMALL = "Small";

    var logoImageFilePathName = string.Format("{0}\\Assets\\Logos\\Chan\\{1}\\{2:0000}.png"
        , installFolderPath
        , LOGO_KIND_SMALL
        , Int32.Parse((string)value));

    // Check for file
    return (File.Exists(logoImageFilePathName))
                ? new BitmapImage(new Uri(logoImageFilePathName))
                : null;
}

public object ConvertBack(object value, Type targetType, object parameter, string culture)
{
    throw new NotSupportedException();
}

只是注意：當你使用像string.Format()這樣的方法時，如果你有一個硬編碼的路徑，你應該把它放在字符串中，如上所述。