-
Rob - Re: Passing VB.NET classes as arguments to VC7 DLLs.
Hi Rob,
Thanks for the clue on the string option. I scanned the on-line
code for a method but I must have missed the construtor overloading
capability. Yeah, the ref was a real pain in the A**. Happily, I
built a custom code generator for the C++ side (parsing a DB schema)
so I can quickly change back to the corrected version in the future.
"Rob Teixeira" <RobTeixeira@@msn.com> wrote:
>
>Hi Patrick,
>
>I knew there was a problem in beta 1 with ref types not being updated properly,
>but I thought this was only with Paramarrays. Apperently, you found out
otherwise
>
>I'll have to remember that.
>
>But the point is that it's a known limitation with Beta1, so don't go and
>change all your DLL's right away. The problem should be fixed soon.
>
>Anyway, you no longer need a String() function. The string class has a constructor
>to do what you want:
>MyString = new String (MyChar, 10)
>
>-Rob
>
>"Patrick Ireland" <ireland@airmail.net> wrote:
>>
>>Hi Jeff,
>>
>>Thanks for the timely response. However, I have already tried the
>>structure method:
>>
>>Public Structure <StructLayout(LayoutKind.Sequential)> DATA_TestPassing
>> Public AccessStatus As Integer
>> Public <MarshalAs(UnmanagedType.ByValArray, SizeConst:=20)> UserName()
>>As Byte
>>End Structure
>>
>>VB.NET gives the error message:
>>
>>"Array initializers are not allowed on a field in a structure"
>>
>>So it seems like a Catch-22. Of course I could have the marshal statement
>>incorrect for the array of bytes.
>>
>>Your comment about filling out the array is very appropriate. I found
that
>>I had to fill every position with something and I could not do it by array
>>subscripting. I filled the array with the System.Text.ASCIIEncoding ().
>>
>>I am disappointed it that I can not find a equivalent to the VB6-- function
>>String$(10,Chr(0)) that produces a string of 10 null characters or what
>>ever character is the second argument. Do you know of one?
>>
>>As always, Jeff you have been the horn of plenty for information but
>>sadly this time the suggested feature has a problem. Admittedly, the
>>problem may be between the ears of this typist.
>>
>>"Jeff Peil" <jpeil@bigfoot.com> wrote:
>>>Hi Patrick,
>>>
>>>"Patrick Ireland" <ireland@airmail.net> wrote in message
>>>news:3aa08054$1@news.devx.com...
>>>> The ByVal was selected because if I used ByRef I do not get the data.
>> I
>>>> suspect that I get a pointer to a pointer to the structure data.
>>>
>>>Doh, I completely overlooked that you were using a class and not a
>>>structure. IIRC this is broken for VB.NET in beta 1 because the out
>>>attribute is not properly supported by the compiler (however it does work
>>>for a structure passed byref which will give the same semantics as a class
>>>passed byval in your case.)
>>>
>>>This does work in C# and ME C++* with a managed class for the parameter
>>as
>>>the beta 1 compiler because those languages does support the out attribute
>>>properly.
>>>
>>>* Beta 1 ME C++ does not properly attribute parameters for global methods,
>>>but it will work when used on a static member of a managed type.
>>>
>>>
>>>Anyways try chaning your VB code to
>>>
>>>Public Structure <StructLayout(LayoutKind.Sequential)> DATA_TestPassing
>>> ' AccessStatus INT
>>> Public AccessStatus As Integer
>>> ' UserName CHAR (16)
>>> Public <MarshalAs(UnmanagedType.ByValArray, SizeConst:=20)> UserName()
>>>As Byte
>>>End Structure
>>>
>>>and
>>>
>>>
>>> Private Declare Function AccessTestPassing _
>>> Lib "c:\Pat\VS7\EXE\TestPassing" _
>>> (ByVal intAccessType As Integer, _
>>> ByRef REC_TestPassing As DATA_TestPassing) _
>>> As Integer
>>>
>>>Of course keep in mind that a freshly created DATA_TestPassing will not
>>have
>>>it's array initialized (you'll want to manually initialize the array on
>>the
>>>managed side of things before using it.)
>>>
>>>
>>
>
Posting Permissions
- You may not post new threads
- You may not post replies
- You may not post attachments
- You may not edit your posts
Forum Rules
|
Top DevX Stories
Easy Web Services with SQL Server 2005 HTTP Endpoints
JavaOne 2005: Java Platform Roadmap Focuses on Ease of Development, Sun Focuses on the "Free" in F.O.S.S.
Wed Yourself to UML with the Power of Associations
Microsoft to Add AJAX Capabilities to ASP.NET
IBM's Cloudscape Versus MySQL
|
Bookmarks