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Converting VB6 Structures to .NETStructure zFuheader Dim Id1(80) As Byte Dim Id2(80) As Byte End Structure However, in .NET, it doesn't let you declare the array size in the structure. I am trying to use an old external .dll that worked with the VB6 structure syntax but doesn't appear to be working when I try and do it in .NET. The problem in a little more detail: I am using a number of "Declare Function" statments to access the functions in the .dll. I am getting an error when I try to pass the structure to one of the functions in the .dll. (Header Pointer is Null or somthing like that). Module MainMod Declare Function initFuHeader Lib "mtsadfconv.dll" Alias "_initFuHeader_VB@4" _ (ByVal zHeader As zFuheader) As Integer Public Structure zFuheader Dim Id1() As Byte 'in VB6 declared to size 80 Dim Id2() As Byte 'in VB6 declared to size 80 End Structure Public Sub Main() Dim zHead As zFuheader Dim result As Integer result = initFuHeader(zHead) '<-- This returns a "result" that Header Pointer is Null End Sub End Module So I'm wondering if the error is because the structure doesn't declare a size for the arrays??? If so, does anyone know a work around? John I wonder if this will work:
Dim zHead As zFuheader redim zHead.Id1(79) Just a thought. Steve Show quoteHide quote "redeagle" <redea***@discussions.microsoft.com> wrote in message news:7F7CCB09-4AE7-440A-811B-AC5E14511D68@microsoft.com... > In VB6, the code for a structure is > > Structure zFuheader > Dim Id1(80) As Byte > Dim Id2(80) As Byte > End Structure > > However, in .NET, it doesn't let you declare the array size in the > structure. > > I am trying to use an old external .dll that worked with the VB6 structure > syntax but doesn't appear to be working when I try and do it in .NET. > > The problem in a little more detail: > > I am using a number of "Declare Function" statments to access the functions > in the .dll. I am getting an error when I try to pass the structure to one > of the functions in the .dll. (Header Pointer is Null or somthing like that). > > Module MainMod > > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias > "_initFuHeader_VB@4" _ (ByVal zHeader As zFuheader) As Integer > > Public Structure zFuheader > Dim Id1() As Byte 'in VB6 declared to size 80 > Dim Id2() As Byte 'in VB6 declared to size 80 > End Structure > > Public Sub Main() > Dim zHead As zFuheader > Dim result As Integer > > result = initFuHeader(zHead) '<-- This returns a "result" that Header > Pointer is Null > > End Sub > > End Module > > So I'm wondering if the error is because the structure doesn't declare a > size for the arrays??? If so, does anyone know a work around? > > John Hi Steve-
Thanks for the reply. Unfortunatly it does not. Although in the interest of complete disclosure, the actual structure I am trying to pass (zFuheader) references another structure that also has an array. Structure zChType Dim Ref() As Byte '8 Dim Res() As Byte '8 End Structure Structure zFuheader Dim Id1() As Byte '20 Dim Id2() As Byte '20 Dim ch() As zChType End Structure Show quoteHide quote "Steve Long" wrote: > I wonder if this will work: > > Dim zHead As zFuheader > > redim zHead.Id1(79) > > Just a thought. > Steve > > "redeagle" <redea***@discussions.microsoft.com> wrote in message > news:7F7CCB09-4AE7-440A-811B-AC5E14511D68@microsoft.com... > > In VB6, the code for a structure is > > > > Structure zFuheader > > Dim Id1(80) As Byte > > Dim Id2(80) As Byte > > End Structure > > > > However, in .NET, it doesn't let you declare the array size in the > > structure. > > > > I am trying to use an old external .dll that worked with the VB6 structure > > syntax but doesn't appear to be working when I try and do it in .NET. > > > > The problem in a little more detail: > > > > I am using a number of "Declare Function" statments to access the > functions > > in the .dll. I am getting an error when I try to pass the structure to > one > > of the functions in the .dll. (Header Pointer is Null or somthing like > that). > > > > Module MainMod > > > > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias > > "_initFuHeader_VB@4" _ (ByVal zHeader As zFuheader) As Integer > > > > Public Structure zFuheader > > Dim Id1() As Byte 'in VB6 declared to size 80 > > Dim Id2() As Byte 'in VB6 declared to size 80 > > End Structure > > > > Public Sub Main() > > Dim zHead As zFuheader > > Dim result As Integer > > > > result = initFuHeader(zHead) '<-- This returns a "result" that > Header > > Pointer is Null > > > > End Sub > > > > End Module > > > > So I'm wondering if the error is because the structure doesn't declare a > > size for the arrays??? If so, does anyone know a work around? > > > > John > > > redeagle wrote:
Show quoteHide quote > In VB6, the code for a structure is Ok... Your dealing with interop, so things are little different. You> > Structure zFuheader > Dim Id1(80) As Byte > Dim Id2(80) As Byte > End Structure > > However, in .NET, it doesn't let you declare the array size in the > structure. > > I am trying to use an old external .dll that worked with the VB6 structure > syntax but doesn't appear to be working when I try and do it in .NET. > > The problem in a little more detail: > > I am using a number of "Declare Function" statments to access the functions > in the .dll. I am getting an error when I try to pass the structure to one > of the functions in the .dll. (Header Pointer is Null or somthing like that). > > Module MainMod > > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias > "_initFuHeader_VB@4" _ (ByVal zHeader As zFuheader) As Integer > > Public Structure zFuheader > Dim Id1() As Byte 'in VB6 declared to size 80 > Dim Id2() As Byte 'in VB6 declared to size 80 > End Structure > > Public Sub Main() > Dim zHead As zFuheader > Dim result As Integer > > result = initFuHeader(zHead) '<-- This returns a "result" that Header > Pointer is Null > > End Sub > > End Module > > So I'm wondering if the error is because the structure doesn't declare a > size for the arrays??? If so, does anyone know a work around? > > John have to add marshalling attributes to this structure, so that the runtime marshaller knows how to pass it to the dll call. Here is what my first stab would be: > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias _ I have to question this declare a little bit. First question I have> "_initFuHeader_VB@4" _ > (ByVal zHeader As zFuheader) As Integer to ask - is this the original VB6 or declare? Because if it is, the As Integer should be As Short. VB.NET changed the size of the data types. A Integer in .NET is 32-bit, not 16-bit (though, this would probably not cause you the error your receiving - though it might give unexpected return results). Further, is this function actually updating this structure? Because if it is, then you should probably be passing it ByRef rather then ByVal. That would most likely cause the error your receiving... > I would probably declare this as:> Public Structure zFuheader > Dim Id1() As Byte 'in VB6 declared to size 80 > Dim Id2() As Byte 'in VB6 declared to size 80 > End Structure <StructLayout (LayoutKind.Sequential)> _ ' not strictly necessary Public Structure zFuheader <MarshalAs (UnmanagedType.ByValArray, SizeConst:=80)> _ Public Id1() As Byte 'in VB6 declared to size 80 <MarshalAs (UnmanagedType.ByValArray, SizeConst:=80)> _ Public Id2() As Byte 'in VB6 declared to size 80 End Structure Anyway, give it a go, and let us know what happens :) -- Tom Shelton Hi Tom-
Thanks for the tips. In VB6 the original declare was "As Long" so I changed it to "As Integer" in ..NET. > Further, is this function actually I actually don't know what its doing. This dll was written by a third party > updating this structure? Because if it is, then you should probably be > passing it ByRef rather then ByVal. That would most likely cause the > error your receiving... software vendor for its customers to use to interact with its proprietary file types. The dll was written in VB6 and they released a "user guide" for the dll. In the user guide, their example uses ByVal. Maybe it is a typo. I will try ByRef. I will also add the Marshalling attributes. I'll keep let you know how it goes... John Show quoteHide quote "Tom Shelton" wrote: > > redeagle wrote: > > In VB6, the code for a structure is > > > > Structure zFuheader > > Dim Id1(80) As Byte > > Dim Id2(80) As Byte > > End Structure > > > > However, in .NET, it doesn't let you declare the array size in the > > structure. > > > > I am trying to use an old external .dll that worked with the VB6 structure > > syntax but doesn't appear to be working when I try and do it in .NET. > > > > The problem in a little more detail: > > > > I am using a number of "Declare Function" statments to access the functions > > in the .dll. I am getting an error when I try to pass the structure to one > > of the functions in the .dll. (Header Pointer is Null or somthing like that). > > > > Module MainMod > > > > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias > > "_initFuHeader_VB@4" _ (ByVal zHeader As zFuheader) As Integer > > > > Public Structure zFuheader > > Dim Id1() As Byte 'in VB6 declared to size 80 > > Dim Id2() As Byte 'in VB6 declared to size 80 > > End Structure > > > > Public Sub Main() > > Dim zHead As zFuheader > > Dim result As Integer > > > > result = initFuHeader(zHead) '<-- This returns a "result" that Header > > Pointer is Null > > > > End Sub > > > > End Module > > > > So I'm wondering if the error is because the structure doesn't declare a > > size for the arrays??? If so, does anyone know a work around? > > > > John > > Ok... Your dealing with interop, so things are little different. You > have to add marshalling attributes to this structure, so that the > runtime marshaller knows how to pass it to the dll call. Here is what > my first stab would be: > > > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias _ > > "_initFuHeader_VB@4" _ > (ByVal zHeader As zFuheader) As Integer > > I have to question this declare a little bit. First question I have > to ask - is this the original VB6 or declare? Because if it is, the As > Integer should be As Short. VB.NET changed the size of the data types. > A Integer in .NET is 32-bit, not 16-bit (though, this would probably > not cause you the error your receiving - though it might give > unexpected return results). Further, is this function actually > updating this structure? Because if it is, then you should probably be > passing it ByRef rather then ByVal. That would most likely cause the > error your receiving... > > > > > Public Structure zFuheader > > Dim Id1() As Byte 'in VB6 declared to size 80 > > Dim Id2() As Byte 'in VB6 declared to size 80 > > End Structure > > I would probably declare this as: > > <StructLayout (LayoutKind.Sequential)> _ ' not strictly necessary > Public Structure zFuheader > <MarshalAs (UnmanagedType.ByValArray, SizeConst:=80)> _ > Public Id1() As Byte 'in VB6 declared to size 80 > > <MarshalAs (UnmanagedType.ByValArray, SizeConst:=80)> _ > Public Id2() As Byte 'in VB6 declared to size 80 > End Structure > > Anyway, give it a go, and let us know what happens :) > > -- > Tom Shelton > > You are the MAN!
I added the Marshalling attributes and changed the "Function Declare" statements from "ByVal" to "ByRef" (that is apparantly a typo throughout the "user guide"). Everything seems to be working now! Thanks again Tom (and Steve) I appreciate your time. John Show quoteHide quote "Tom Shelton" wrote: > > redeagle wrote: > > In VB6, the code for a structure is > > > > Structure zFuheader > > Dim Id1(80) As Byte > > Dim Id2(80) As Byte > > End Structure > > > > However, in .NET, it doesn't let you declare the array size in the > > structure. > > > > I am trying to use an old external .dll that worked with the VB6 structure > > syntax but doesn't appear to be working when I try and do it in .NET. > > > > The problem in a little more detail: > > > > I am using a number of "Declare Function" statments to access the functions > > in the .dll. I am getting an error when I try to pass the structure to one > > of the functions in the .dll. (Header Pointer is Null or somthing like that). > > > > Module MainMod > > > > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias > > "_initFuHeader_VB@4" _ (ByVal zHeader As zFuheader) As Integer > > > > Public Structure zFuheader > > Dim Id1() As Byte 'in VB6 declared to size 80 > > Dim Id2() As Byte 'in VB6 declared to size 80 > > End Structure > > > > Public Sub Main() > > Dim zHead As zFuheader > > Dim result As Integer > > > > result = initFuHeader(zHead) '<-- This returns a "result" that Header > > Pointer is Null > > > > End Sub > > > > End Module > > > > So I'm wondering if the error is because the structure doesn't declare a > > size for the arrays??? If so, does anyone know a work around? > > > > John > > Ok... Your dealing with interop, so things are little different. You > have to add marshalling attributes to this structure, so that the > runtime marshaller knows how to pass it to the dll call. Here is what > my first stab would be: > > > Declare Function initFuHeader Lib "mtsadfconv.dll" Alias _ > > "_initFuHeader_VB@4" _ > (ByVal zHeader As zFuheader) As Integer > > I have to question this declare a little bit. First question I have > to ask - is this the original VB6 or declare? Because if it is, the As > Integer should be As Short. VB.NET changed the size of the data types. > A Integer in .NET is 32-bit, not 16-bit (though, this would probably > not cause you the error your receiving - though it might give > unexpected return results). Further, is this function actually > updating this structure? Because if it is, then you should probably be > passing it ByRef rather then ByVal. That would most likely cause the > error your receiving... > > > > > Public Structure zFuheader > > Dim Id1() As Byte 'in VB6 declared to size 80 > > Dim Id2() As Byte 'in VB6 declared to size 80 > > End Structure > > I would probably declare this as: > > <StructLayout (LayoutKind.Sequential)> _ ' not strictly necessary > Public Structure zFuheader > <MarshalAs (UnmanagedType.ByValArray, SizeConst:=80)> _ > Public Id1() As Byte 'in VB6 declared to size 80 > > <MarshalAs (UnmanagedType.ByValArray, SizeConst:=80)> _ > Public Id2() As Byte 'in VB6 declared to size 80 > End Structure > > Anyway, give it a go, and let us know what happens :) > > -- > Tom Shelton > > 
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