Converting a byte() array to a double in VB.Net

Question

I have this situation. I have a real stored in a varbinary field in a sql 2005 database. As I can't convert a varbinary to a real in sql 2005, I'm trying to do that in vb.net.

That field gets stored as a byte() array in a DataTable.

Now I would like to read that byte() into a double, or decimal variable. But I don't have much of a clue on how to do that...

Answer 1

It really depends on how it's stored, but BitConverter.ToDouble may be your friend. That's assuming it's in IEE754 format. Where are you getting the data from in the first place?

Answer 2

I don't know VB.net well, but know the .NET libraries.

Wrap the byte[] in a MemoryStream and wrap that in a BinaryReader. Then use the BinaryReader.ReadDouble() method. See here and here for MSDN pages.

Edit in response to this

You are looking for a piece of code looking like this:

'declare a test array
Dim testArray As Byte() = {0, 0, 0, 0}
'wrap it into a memory stream
Dim memStream As MemoryStream = new MemoryStream(testArray)
'wrap the stream in a binary reader
Dim bReader As BinaryReader = new BinaryReader(memStream)
'read a 32bit integer from the stream using the reader
Dim count As Integer = bReader.ReadInt32()

Answer 3

Public Function GetDateFromBytes(ByRef value() As Byte, _
                                    ByRef startindex As Int32) As Date
    'create a aray of Ints
    Dim IntValues() As Int32 = {BitConverter.ToInt32(value, startindex), _
                                    BitConverter.ToInt32(value, (startindex + 7)), _
                                    BitConverter.ToInt32(value, startindex + 15), _
                                     BitConverter.ToInt32(value, startindex + 31)}

    Return Date.FromBinary(New Decimal(IntValues))

End Function