从MusicBrainz检索数据(从C#转换代码) [英] Retrieve data from MusicBrainz (code translated from C#)

问题描述

嗨！

我已经将一些代码从C#转换为VB.我在这里找到了代码 http://www.codeproject.com/KB/webservices/FaisonMusicExplorer1.aspx?msg=4036510#xx4036510xx
我尝试从musicbrainz服务器检索艺术家ID，但是在VB中使用翻译后的代码时出现错误.

当我在C#中查看字符串值xpath时，它的值是"//mb:artist [mb:name =" The Beatles \] .此后，它将毫无问题地检索艺术家ID.

现在，当我尝试在VB中执行相同操作时，它不会检索艺术家ID.

第一个代码块是我找到的代码块，第二个是我对第一个代码块的翻译.我看不到我在做什么错...

Hi!

I have translated some code from C# to VB. I found the code here http://www.codeproject.com/KB/webservices/FaisonMusicExplorer1.aspx?msg=4036510#xx4036510xx
I try to retrieve the artist ID from the musicbrainz server, but i get an error when i use my translated code in VB.

When I look at the string value xpath in C# it holds the value "//mb:artist[mb:name="The Beatles\]". After that it retrieves the artist ID without any problem.

Now, when I try to do the same in VB it does not retrieve the artist ID.

The first code-block is the one I found, the second is my translation of the first code-block. I can''t see what i''m doing wrong...

// find the artist ID of a given artist.
   public static string FindArtistId(string name)
   {
     try
     {
       string uri = string.Format("http://musicbrainz.org/ws/1/artist/?query={0}&type=xml", name);
       XPathDocument doc = new XPathDocument(uri);
       XPathNavigator nav = doc.CreateNavigator();
       XmlNamespaceManager nsmgr = new XmlNamespaceManager(nav.NameTable);
       nsmgr.AddNamespace("mb", "http://musicbrainz.org/ns/mmd-1.0#");
       string xpath = string.Format("//mb:artist[mb:name=\"{0}\"]", name);   // The artist name is case-sensitive!
       XPathNodeIterator ni = nav.Select(xpath, nsmgr);
       if (!ni.MoveNext()) return null;
       XPathNavigator current = ni.Current;
       return current.GetAttribute("id", nsmgr.DefaultNamespace);
     }
     catch (WebException wex)
     {
       MessageBox.Show(string.Format("A communication error occurred ({0}). The MusicBrainz server might be down.", wex.Status), "Couldn't resolve artist name");
       return null;
     }
     catch (Exception ex)
     {
       MessageBox.Show(string.Format("An error occurred ({0}). The error may have been caused by bad data from the MusicBrainz server.", ex.Message), "Couldn't resolve artist name");
       return null;
     }
   }

Public Function FindArtistId(ByVal name As String) As String
        Try
            Dim uri As String = String.Format("http://musicbrainz.org/ws/1/artist/?query={0}&type=xml", name)
            Dim doc As XPathDocument = New XPathDocument(uri)
            Dim nav As XPathNavigator = doc.CreateNavigator()
            Dim nsmgr As XmlNamespaceManager = New XmlNamespaceManager(nav.NameTable)
            nsmgr.AddNamespace("mb", "http://musicbrainz.org/ns/mmd-1.0#")
            Dim xpath As String = String.Format("//mb:artist[mb:name=""{0}""]", name) 'The artist name is case-sensitive!
            Dim ni As XPathNodeIterator = nav.Select(xpath, nsmgr)
            If ni.MoveNext() Then Return Nothing
            Dim current As XPathNavigator = ni.Current
            Return current.GetAttribute("id", nsmgr.DefaultNamespace)
        Catch wex As WebException
            MessageBox.Show(String.Format("A communication error occurred ({0}). The MusicBrainz server might be down.", wex.Status), "Couldn't resolve artist name")
            Return Nothing
        Catch ex As Exception
            MessageBox.Show(String.Format("An error occurred ({0}). The error may have been caused by bad data from the MusicBrainz server.", ex.Message), "Couldn't resolve artist name")
            Return Nothing
        End Try
    End Function

推荐答案

if (!ni.MoveNext()) return null;

与
不同

is not the same as

If ni.MoveNext() Then Return Nothing

尝试

try

If Not ni.MoveNext() Then
    Return Nothing
End If

重要的是Not ，但我要补充一点仍然是 End If .

It''s the Not that is important, but I would add the End If anyway.

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