Converting VB6 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. See the List of .NET Methods and Cross-reference between Functions and .NET Methods.

Long types in VB6 must be changed to Integer in VB.NET. All integers in CryptoSys API are 32-bit signed integers. You will get an exception or garbage results if you use a VB.NET Long type.

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)

Annotated example:

VB6/VBA

 1 Debug.Print "Testing HASH_HexFromHex ..."
 2 Dim strDigest As String
 3 Dim nRet As Long
 4 Dim strData As String
 5 strDigest = String(API_SHA1_CHARS, " ")
 6 strData = "616263"
 7 nRet = HASH_HexFromHex(strDigest, Len(strDigest), strData, API_HASH_SHA1)
 8 Debug.Print strDigest

Comments:

• Line 5: Need to pre-dimension the output string strDigest or else!
• Line 7: Integer error code is returned: nRet = 0 indicates success (for this function).
• Line 7: Use API_HASH_SHA1 flag to specify hash algorithm option.

Output

Testing HASH_HexFromHex ...
a9993e364706816aba3e25717850c26c9cd0d89d

VB.NET

 1 Console.WriteLine("Testing HASH_HexFromHex ...")
 2 Dim strDigest As String
 3 ''Dim nRet As Integer
 4 Dim strData As String
 5 ''strDigest = String(API_SHA1_CHARS, " ")
 6 strData = "616263"
 7 strDigest = Hash.HexFromHex(strData, HashAlgorithm.Sha1)
 8 Console.WriteLine(strDigest)

Comments:

• Line 3: Integer error code is not used.
• Line 5: No need to pre-dimension the output string.
• Line 7: Output is returned directly as a string: strDigest.Length > 0 indicates success.
• Line 7: Use HashAlgorithm property to specify hash algorithm option.

Most methods in VB.NET are "all-in-one" stateless methods and so do not require the creation of an object. These are called in a one-off manner. The incremental stateful functions in VB6 that use a context handle (those 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()

[Contents] [Index]