Imports System.IO

Imports System.Xml

Imports System.Data.SqlClient

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim mySet As SettingsXML = New SettingsXML("test")

        'for a new file, it will add 'defaultkey1' and 'defaultvalue1' rows

        ' so you can see contents in your file regardless

        'adding a new row

        mySet.AddOrUpdtSetting("myNewKey1", "myNewValue1")

        'adding another row

        mySet.AddOrUpdtSetting("myNewKey2", "myNewValue2")

        'changing the value of the first row to ensure the search works, which it does

        mySet.AddOrUpdtSetting("mynewkey1", "ChangedValue1")

    End Sub

End Class

Public Class SettingsXML

    Private fname As String

    Private xmldata As DataSet

    Public Property filename() As String

        Get

            Return fname

        End Get

        Set(ByVal value As String)

            fname = value

        End Set

    End Property

    Public Sub New(ByVal filename As String)

        If Right(filename, 4) <> ".XML" Then

            filename = filename & ".XML"

        End If

        fname = filename

        xmldata = New DataSet

        If Not File.Exists(filename) Then

            xmldata.Tables.Add("AppSettings")

            xmldata.Tables(0).Columns.Add("Key")

            xmldata.Tables(0).Columns.Add("Value")

            Dim r1 As DataRow = xmldata.Tables(0).NewRow

            r1.Item(0) = "defaultkey1"

            r1.Item(1) = "defaultvalue1"

            xmldata.Tables(0).Rows.Add(r1)

            xmldata.WriteXmlSchema(filename)

            xmldata.WriteXml(filename)

        Else

            xmldata.ReadXmlSchema(filename)

            xmldata.ReadXml(filename)

        End If

    End Sub

    Private Sub AddNewRow(ByVal newkey As String, ByVal newvalue As String)

        Dim r1 As DataRow = xmldata.Tables(0).NewRow

        r1.Item(0) = newkey

        r1.Item(1) = newvalue

        xmldata.Tables(0).Rows.Add(r1)

    End Sub

    Public Sub AddOrUpdtSetting(ByVal searchkey As String, ByVal newvalue As String)

        xmldata.Tables(0).PrimaryKey = New DataColumn() {xmldata.Tables(0).Columns("Key")}

        Dim r1 As DataRow = xmldata.Tables(0).Rows.Find(searchkey)

        If Not r1 Is Nothing Then

            'Console.WriteLine("Updated: " & searchkey & " with old value " & r1.Item(1) & " to new value " & newvalue)

            r1.Item(1) = newvalue

        Else

            'Console.WriteLine("Inserted: " & searchkey & " value: " & newvalue)

            AddNewRow(searchkey, newvalue)

        End If

        xmldata.WriteXml(fname)

    End Sub

End Class