Value of type '1-dimensional array of Byte' cannot be converted to 'Byte

Question

I am having a problem with code when assigning values. I continue to get the above error on line 3. Where am I going wrong?

Dim Buffer As Byte() = New Byte(&H2710 - 1) {}
        Dim numRef As Byte
        numRef = Buffer
        Dim num2 As Integer
        Dim seemNum As UInt32 = Convert.ToUInt32(hexSeem, &H10)
        If (seemNum <> 0) Then
            num2 = Seem_Read(seemNum, recNum, startOff, bytes, numRef)
        Else
            num2 = Seem_Read(0, recNum, startOff, bytes, numRef)
        End If
        If num2 <> -1 Then
            Dim buffer3 As Byte() = New Byte(num2 - 1) {}
            Dim i As Integer
            For i = 0 To num2 - 1
                buffer3(i) = buffer(i)
            Next i
            Return buffer3
        End If
        Return Nothing

Thanks

Alan · Answer

Generally speaking it's not easy (and sometimes virtually impossible) to translate unsafe code in C# into an equivalent form in VB.Net. However all the unsafe code is doing here is 'pinning' the byte array so it doesn't move in memory and then taking its address which it passes to the unmanaged function Seem_Read() so that it can fill in the data. So what I'd suggest you do from VB.Net is the following. First change the signature of the unmanaged function so it takes an IntPtr rather than a Byte: Public Declare Function Seem_Read Lib p2kapi2.dll (ByVal SeemNum As UInt32 ByVal RecordNum As UInt32 ByVal StartOff As UInt32 ByVal Bytes As UInt32 IntPtr ptrData ) As Integer Then change your VB function as follows (changed code highlighted): Public Shared Function SeemRead(ByVal hexSeem As String ByVal recNum As UInt32 ByVal startOff As UInt32 ByVal bytes As UInt32) As Byte() Dim Buffer As Byte() = New Byte(&H2710 - 1) {} Dim gch As GCHandle = GCHandle.Alloc(Buffer GCHandleType.Pinned) Dim numRef As IntPtr = gch.AddrOfPinnedObject() Dim num2 As Integer Dim seemNum As UInt32 = Convert.ToUInt32(hexSeem &H10) If (seemNum 0) Then num2 = Seem_Read(seemNum recNum startOff bytes numRef) Else num2 = Seem_Read(0 recNum startOff bytes numRef) End If If num2 -1 Then Dim buffer3 As Byte() = New Byte(num2 - 1) {} Dim i As Integer For i = 0 To num2 - 1 buffer3(i) = buffer(i) Next i gch.Free() Return buffer3 End If gch.Free() Return Nothing End Function

Celldet · Answer

Thank you for the code. There is not an exception currently but the code actually returns an error from the function. I have posted the original code from C# and it must be an error in my conversion to VB.NET that is the problem. My function returns a -1 which indicates an error. The numRef is actually a pointer. Here are the each of the variable def in the function that returns. Here is the call to the dll Public Declare Function Seem_Read Lib p2kapi2.dll (ByVal SeemNum As UInt32 ByVal RecordNum As UInt32 ByVal StartOff As UInt32 ByVal Bytes As UInt32 ByRef ptrData As Byte) As Integer SeemNum - Seem cell number RecordNum - Seem record number StartOffset - Offset for seem reading from (0 - from cell beginning) Bytes - Bytes count for reading (0 - read from beginning to end) ptrData - pointer to a buffer for receiving seem cell data If Bytes parameter not specified then buffer length must be >= 2710h bytes Returns count of read bytes or -1 on error. Original code c# public static unsafe byte [] SeemRead ( string hexSeem uint recNum uint startOff uint bytes) { byte [] buffer = new byte [ 0x2710 ]; fixed ( byte * numRef = buffer ) { int num2 ; uint seemNum = Convert . ToUInt32 ( hexSeem  0x10 ); if ( seemNum != 0 ) { num2 = Seem_Read ( seemNum  recNum  startOff  bytes  numRef ); } else { num2 = Seem_Read ( 0  recNum  startOff  bytes  numRef ); } if ( num2 != -1 ) { byte [] buffer3 = new byte [ num2 ]; for ( int i = 0 ; i num2 ; i ++) { buffer3 [ i ] = buffer [ i ]; } return buffer3 ; } return null ; } } My code in VB.NET Public Shared Function SeemRead(ByVal hexSeem As String ByVal recNum As UInt32 ByVal startOff As UInt32 ByVal bytes As UInt32) As Byte() Dim Buffer As Byte() = New Byte( &H2710 - 1 ) {} Dim numRef As Integer numRef = Buffer.Length Dim num2 As Integer Dim seemNum As UInt32 = Convert.ToUInt32(hexSeem &H10) If (seemNum 0) Then num2 = Seem_Read(seemNum recNum startOff bytes numRef) Else num2 = Seem_Read(0 recNum startOff bytes numRef) End If If num2 -1 Then Dim buffer3 As Byte() = New Byte(num2 - 1) {} Dim i As Integer For i = 0 To num2 - 1 buffer3(i) = buffer(i) Next i Return buffer3 End If Return Nothing End Function

Alan · Answer

Well as the error message says numRef is declared to be a Byte variable and Buffer is a Byte array variable and so can't be converted to a single Byte. You could prevent the error with: Dim numRef As Byte() numRef = Buffer However whilst I can't make much sense of the code I suspect from its name and the way it's used that numRef may be the length of the Byte buffer. If that's the case then you'd want: Dim numRef As Integer numRef = Buffer.Length