Important points when converting VB6 code to VB.NET

• To use CryptoSys API in VB.NET, you call .NET methods instead of VB6 functions. In almost all cases, a VB6 function like FOO_Barbaz is replaced by the .NET method Foo.Barbaz. The .NET methods generally have fewer parameters and different return values than the equivalent VB6 function.

• Long types in VB6 must be changed to Integer in VB.NET.

• Functions that in VB6 would have output to a pre-dimensioned string or byte array will return that string or byte array directly in VB.NET. For such methods in VB.NET, an error condition is indicated by returning an empty string or byte array.

  VB6/VBA

  ReDim abDigest(API_MAX_HASH_BYTES - 1)
  nRet = HASH_Bytes(abDigest(0), API_MAX_HASH_BYTES, abMessage(0), nMsgLen, API_HASH_MD5)
  

  VB.NET

  abDigest = Hash.BytesFromBytes(abMessage, HashAlgorithm.Md5)
  

• Most methods in VB.NET are stateless and do not require the creation of an object. These are called in a one-off manner. Those stateful functions in VB6 that use a context handle created by an Init function and closed by a Final function are replaced in VB.NET by objects that must be instantiated and then disposed of. Be careful with error conditions because the VB6 Init functions return zero on error, but the VB.NET Init methods return either True or zero on success.

  VB6/VBA

  Dim hContext as Long
  hContext = Foo_Init(...)
  If hContext = 0 Then
      nError = Foo_InitError()
      ...
  End If
  For i = 1 To n
      nRet = Foo_Update(hContext, abBlock(0), nBlockLen)
  Next
  nRet = Foo_Final(hContext)
  

  VB.NET

  Dim oFoo As Foo = Foo.Instance()
  nRet = oFoo.InitEncrypt(...)
  If nRet <> 0
      nError = oFoo.ErrCode
      ...
  End If
  For i = 1 To n
      abBlock = oFoo.Update(abBlock)
  End If
  oFoo.Dispose()