[Silverlight Only] How to load UTF-7 CSV data when not supported by Silverlight 4+

1 posts, 0 answers
  1. Graeme
    Graeme avatar
    21 posts
    Member since:
    May 2012

    Posted 18 Nov 2014 Link to this post

    I had a problem with loading & decoding UTF-7 data from a CSV file into Silverlight's RADSpreadProcessing. Special characters like 'é' were being flagged as invalid by the Microsoft UTF-8 decoder in Silverlight. WPF on the other hand supports UTF-7 decoding.

    With the help of Nikolay Demirev (Telerik support) he pointed me in the right direction with this Microsoft information: Understanding Encodings for Silverlight

    Below is the solution that I came up with to auto-identify the encoding and handle UTF-7 encoded CSV files. I hope that it helps others.

        Sub ProcessData()
            Dim FormatProvider = New CsvFormatProvider
            With FormatProvider
                With .Settings
                    .Delimiter = ","
                    .Quote = """"
                    .HasHeaderRow = True
                    .Encoding = New System.Text.UnicodeEncoding
                End With
            End With
            Dim Filename As String = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "Telerik Test.csv")
            Dim WB As Workbook = LoadWB(Filename, FormatProvider)
            '-- do something with the loaded data...
        End Sub
        Function LoadWB(FileName As String, FormatProvider As CsvFormatProvider) As Workbook
            If Not File.Exists(FileName) Then
                Throw New FileNotFoundException(String.Format("{0} Not Found.", FileName))
            End If
            Dim WB As Workbook
            If GetFileEncoding(FileName) Is Encoding.UTF8 Then
                WB = FormatProvider.Import(GetUTF8(FileName))
                Using Data As FileStream = New FileStream(FileName, FileMode.Open)
                    WB = FormatProvider.Import(Data)
                End Using
            End If
            Return WB
        End Function
        Function GetUTF8(Filename As String) As String
            Dim encodedBytes() As Byte = File.ReadAllBytes(Filename)
            Dim enc8 As Encoding = New UTF8Encoding(False, True)
            Dim decodedString As String = String.Empty
                decodedString += enc8.GetString(encodedBytes, 0, encodedBytes.Length)
            Catch e As DecoderFallbackException
                Dim sb As New StringBuilder
                For Each b As Byte In encodedBytes
                decodedString = sb.ToString()
            End Try
            Return decodedString
        End Function
        Public Shared Function GetFileEncoding(srcFile As String) As Encoding
            ' Use Default of Encoding.Default (Ansi CodePage)
            Dim enc As Encoding = Encoding.UTF8
            ' Detect byte order mark if any - otherwise assume default
            Dim buffer As Byte() = New Byte(4) {}
            Dim file As New FileStream(srcFile, FileMode.Open)
            file.Read(buffer, 0, 5)
            If buffer(0) = &HEF AndAlso buffer(1) = &HBB AndAlso buffer(2) = &HBF Then
                enc = Encoding.UTF8
            ElseIf buffer(0) = &HFF AndAlso buffer(1) = &HFE Then
                enc = Encoding.Unicode
            ElseIf (buffer(0) = &HFE AndAlso buffer(1) = &HFF) Then
                enc = Encoding.BigEndianUnicode
            ElseIf buffer(0) = 0 AndAlso buffer(1) = 0 AndAlso buffer(2) = &HFE AndAlso buffer(3) = &HFF Then
                enc = Encoding.Unicode
            ElseIf buffer(0) = &H2B AndAlso buffer(1) = &H2F AndAlso buffer(2) = &H76 Then
                enc = Encoding.UTF8
            End If
            Return enc
        End Function

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