N
Nataraj1978
I have a requirement to use a dll written in Visual C++ 6.0 in my C#
application. In order to establish the link between my application and the
dll, I have written a ATL COM Component in Visual C++.NET [visual studio .NET
version 8]. This COM component is referenced in my C# application. The COM
component statically links with the 6.0 dll.
I am facing problems in passing data from C# to the dll through the COM
component.
Description:
1. The dll exposes a function as:
__declspec(dllexport) int __stdcall ProblemFunction(int param1, BYTE param2,
BYTE param3, BYTE *param4, DWORD *param5);
2. In the COM wrapper component, I have declared an interface method as:
[id(25), helpstring("method ProblemFunc")] HRESULT ProblemFunc([in] SHORT
param1, [in] BYTE param2, [in] BYTE param3, [in, out] BYTE* param4, [in, out]
LONG* param5, [out, retval] BYTE* param6);
where, param6 is used to return the value returned by dll function to the C#
client application.
The implementation of this interface function is given below:
STDMETHODIMP
Wrapper:roblemFunc(SHORT param1, BYTE param2, BYTE param3, BYTE* param4,
LONG* param5, BYTE* param6)
{
*param6 = ProblemFunction(param1, param2, param3, param4, (DWORD*)param5);
return S_OK;
}
3. In the C# client application, I am calling the COM function as:
byte returnValue = DllWrapperObject.ProblemFunc(value1, (byte)value2, (byte)
value3, ref value4, ref value5);
Here, I am facing problems passing value4 and value5 because:
a. For value4 I need to pass a structure.
b. For value5 I need to pass the size of the structure being passed in value4.
The structure to be passed is as required by the dll. The C++ structure is:
typedef struct
{
DWORD var1;
DWORD var2;
struct
{
DWORD var3;
char var4[16];
DWORD var5;
} var6[3];
} TEST_STRUCT;
I wrote the structure's equivalent in C# as a class as I had to create an
array. The C# implementation of the above given structure is:
internal class InnerStruct
{
long var3;
char[] var4 = new char[16];
long var5;
internal static int GetSizeOfClass()
{
return (sizeof(long) + sizeof(char) * 16 + sizeof(long));
}
}
internal class TestStruct
{
long var1;
long var2;
InnerStruct[] var6 = new InnerStruct[3];
internal static int GetSizeOfClass()
{
return (sizeof(long) * 2 + InnerStruct.GetSizeOfClass() * 3);
}
}
Questions:
1. Is there any better way to define the structure equivalent in C#?
2. How can I get the size of the structure/class for passing it to the dll?
3. How to pass the handle of the structure/class object from C# to the dll so
that it can fill it up and return it to the client app for future usage?
application. In order to establish the link between my application and the
dll, I have written a ATL COM Component in Visual C++.NET [visual studio .NET
version 8]. This COM component is referenced in my C# application. The COM
component statically links with the 6.0 dll.
I am facing problems in passing data from C# to the dll through the COM
component.
Description:
1. The dll exposes a function as:
__declspec(dllexport) int __stdcall ProblemFunction(int param1, BYTE param2,
BYTE param3, BYTE *param4, DWORD *param5);
2. In the COM wrapper component, I have declared an interface method as:
[id(25), helpstring("method ProblemFunc")] HRESULT ProblemFunc([in] SHORT
param1, [in] BYTE param2, [in] BYTE param3, [in, out] BYTE* param4, [in, out]
LONG* param5, [out, retval] BYTE* param6);
where, param6 is used to return the value returned by dll function to the C#
client application.
The implementation of this interface function is given below:
STDMETHODIMP
Wrapper:roblemFunc(SHORT param1, BYTE param2, BYTE param3, BYTE* param4,
LONG* param5, BYTE* param6)
{
*param6 = ProblemFunction(param1, param2, param3, param4, (DWORD*)param5);
return S_OK;
}
3. In the C# client application, I am calling the COM function as:
byte returnValue = DllWrapperObject.ProblemFunc(value1, (byte)value2, (byte)
value3, ref value4, ref value5);
Here, I am facing problems passing value4 and value5 because:
a. For value4 I need to pass a structure.
b. For value5 I need to pass the size of the structure being passed in value4.
The structure to be passed is as required by the dll. The C++ structure is:
typedef struct
{
DWORD var1;
DWORD var2;
struct
{
DWORD var3;
char var4[16];
DWORD var5;
} var6[3];
} TEST_STRUCT;
I wrote the structure's equivalent in C# as a class as I had to create an
array. The C# implementation of the above given structure is:
internal class InnerStruct
{
long var3;
char[] var4 = new char[16];
long var5;
internal static int GetSizeOfClass()
{
return (sizeof(long) + sizeof(char) * 16 + sizeof(long));
}
}
internal class TestStruct
{
long var1;
long var2;
InnerStruct[] var6 = new InnerStruct[3];
internal static int GetSizeOfClass()
{
return (sizeof(long) * 2 + InnerStruct.GetSizeOfClass() * 3);
}
}
Questions:
1. Is there any better way to define the structure equivalent in C#?
2. How can I get the size of the structure/class for passing it to the dll?
3. How to pass the handle of the structure/class object from C# to the dll so
that it can fill it up and return it to the client app for future usage?