XmlNode AppendChild可在C＃中工作，但不能在VB.Net中工作

Question

I keep running into the below error message in vb.net, but in the same project done in C#, this works perfectly. After manually converting the project from C# to VB, this is where the error arises. Any suggestions would be appreciated.

Vb.Net:

Const App_ID As String = "WindowsToastTest"
Private Sub Button_Click(sender As Object, e As RoutedEventArgs)


    ' Get a toast XML template
    Dim toastXml As XmlDocument = ToastNotificationManager.GetTemplateContent(ToastTemplateType.ToastImageAndText03)

    ' Fill in the text elements

    Dim stringElements As XmlNodeList = toastXml.GetElementsByTagName("text")
    For i As Integer = 0 To stringElements.Length
        stringElements(i).AppendChild(toastXml.CreateTextNode("Line " + i))
    Next

    ' Specify the absolute path to an image
    Dim imagePath As String = "file:///" + Path.GetFullPath("toastImageAndText.png")
    Dim imageElements As XmlNodeList = toastXml.GetElementsByTagName("image")
    imageElements(0).Attributes.GetNamedItem("src").NodeValue = imagePath

    ' Create the toast And attach event listeners
    Dim toast As ToastNotification = New ToastNotification(toastXml)

    ' Show the toast. Be sure to specify the AppUserModelId on your application's shortcut!
    ToastNotificationManager.CreateToastNotifier(APP_ID).Show(toast)



End Sub

C#:

namespace ToastSample
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    private const String APP_ID = "ToastSample";
    public MainWindow()
    {
        InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        // Get a toast XML template
        XmlDocument toastXml = ToastNotificationManager.GetTemplateContent(ToastTemplateType.ToastImageAndText03);

        // Fill in the text elements
        XmlNodeList stringElements = toastXml.GetElementsByTagName("text");
        for (int i = 0; i < stringElements.Length; i++)
        {
            stringElements[i].AppendChild(toastXml.CreateTextNode("Line " + i));
        }

        // Specify the absolute path to an image
        String imagePath = "file:///" + Path.GetFullPath("toastImageAndText.png");
        XmlNodeList imageElements = toastXml.GetElementsByTagName("image");
        imageElements[0].Attributes.GetNamedItem("src").NodeValue = imagePath;

        // Create the toast and attach event listeners
        ToastNotification toast = new ToastNotification(toastXml);

        // Show the toast. Be sure to specify the AppUserModelId on your application's shortcut!
        ToastNotificationManager.CreateToastNotifier(APP_ID).Show(toast);
    }

}
}

Answer 1

The problem isn't with the XML, it's with your string concatenation. Concat strings by & and + in VB.Net When you use string + number in vb it tries to cast the string to a number, which is why you're getting the error 'Conversion from string "Line" to type 'Double' is invalid'. Instead use &:

stringElements(i).AppendChild(toastXml.CreateTextNode("Line " & i))

Hope that helps.

Answer 2

The + operator is different between languages.

To concatenate in VB, use & instead.

Dim stringElements As XmlNodeList = toastXml.GetElementsByTagName("text")
For i As Integer = 0 To stringElements.Length
    stringElements(i).AppendChild(toastXml.CreateTextNode("Line " & i))
Next