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VB.NET Serialize Hashtable (nonbinary)

Posted on 2009-04-15
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Last Modified: 2013-11-08
I'm very new to VB. Only been using it for about a week. I've got about 9 years of Perl behind me so I can understand concepts perfectly, I just don't know the methods for VB or the 'lingo', be gentle lol.

I've got a basic hash setup something like key: blahblah, value: 8752.  I'm trying to figure out how to drop that out to human-readable .xml. (The data was originally .INI, if that helps at all) Keys are always strings, values are always integers, no chance of any duplicates, ever.

Any help is greatly appreciated as my friend's comment was waay out of my league, creating classes with properties and whatnot. Sounds like rolling my own form of a Hashtable.
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Question by:Craz3d
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Expert Comment

by:Wayne Taylor (webtubbs)
Comment Utility
Depending on the flavour of XML you want, I have two options....
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Expert Comment

by:Wayne Taylor (webtubbs)
Comment Utility
Use the XmlSerializer object....
    Public Shared Function HashToXml(ByVal hash As Hashtable) As String

 

        Dim entries As New List(Of Entry)(hash.Count)

        For Each key As Object In hash.Keys

            entries.Add(New Entry(key, hash(key)))

        Next

 

        Dim sb As New Text.StringBuilder

        Dim writer As New System.IO.StringWriter(sb)

        Dim serializer As New XmlSerializer(GetType(List(Of Entry)))

        serializer.Serialize(writer, entries)

 

        Return sb.ToString

 

    End Function

 

    Public Class Entry

        Public Key As Object

        Public Value As Object

        Public Sub New()

            'nothing here

        End Sub

        Public Sub New(ByVal key As Object, ByVal value As Object)

            Me.Key = key

            Me.Value = value

        End Sub

    End Class

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Wayne Taylor (webtubbs) earned 500 total points
Comment Utility
2) Create a DataSet, populate it with the HashTable data, then use the DataSet.WriteToXML method...
    Public Shared Function HashToXML(ByVal ht As Hashtable) As String

 

        Dim sb As New Text.StringBuilder

        Dim sr As New IO.StringWriter(sb)

 

        Dim ds As New DataSet("HashToXML")

        Dim dt As New DataTable("Item")

        dt.Columns.Add("Key")

        dt.Columns.Add("Value")

        ds.Tables.Add(dt)

 

        For Each key As Object In ht.Keys

            dt.Rows.Add(New Object() {key.ToString, ht(key).ToString})

        Next

 

        dt.WriteXml(sr)

 

        Return sb.ToString

 

    End Function

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Author Comment

by:Craz3d
Comment Utility
Tried both methods, the first was a bit more obfuscated than I'd like. The second didn't actually put out any newlines in the file but (unless I'm mistaken) I can just do that by hand, it's no biggy.

How might I pull them back into a hashtable?
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Expert Comment

by:Wayne Taylor (webtubbs)
Comment Utility
>>The second didn't actually put out any newlines in the file

In fairness, XML files are normally not meant for viewing directly, but if you do, use the default program designated for opening XML files (which is normally Internet Explorer, although any browser will do). Doing so will present the XML in an easy to read format - with line breaks.

To read the XML back to a HashTable, you can use this function....
    Public Function XMLtoHashTable(ByVal xmlStr As String) As Hashtable
 

        Dim hash As New Hashtable

        Dim sr As New IO.StringReader(xmlStr)

        Dim ds As New DataSet

        ds.ReadXml(sr)

        sr.Close()

        sr.Dispose()

        For Each dr As DataRow In ds.Tables("Item").Rows

            hash.Add(dr("Key"), dr("Value"))

        Next

        ds.Dispose()

        Return hash
 

    End Function

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Author Comment

by:Craz3d
Comment Utility
Thank you webtubbs.
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