P/Invoke and NotSupportedExceptions

[BVayer]

I am trying to P/Invoke a Motorola API and all I keep getting is the
NotSupportException.

The api uses a struct to manipulate the data and returns a DWORD
variable which I converted to uint.

The Struct is made up of several variables of type WORD and 3 variables
which are TCHAR of a fixed length. Those I have as strings; I also
tried them as StringBuilders. The variables which are of type WORD I
am converting to UInt16's.

The API:
typedef TCHAR DIAG_BATTERY_STRINGS_T [BATTERY_STRINGS_SIZE];

typedef struct tagMAIN_BATTERY_PACK_PARAMS
{
WORD wRemainingCapacity;
WORD wCycleCount;
WORD wTimeToFull;
WORD wSerialNumber;
WORD wRatedCapacity;
WORD wActualCapacity;
WORD wManufactureDate;
WORD wBatteryStatus;

DIAG_BATTERY_STRINGS_T ManufactureName;
DIAG_BATTERY_STRINGS_T DeviceName;
DIAG_BATTERY_STRINGS_T DeviceChemistry;

}


MY CODE:
[DllImport("DiagApi.dll")]
private static extern uint DiagBatGetBatteryPackParams( ref
MAIN_BATTERY_PACK_PARAMS MainBatteryInfo);

[StructLayout(LayoutKind.Sequential)]
public struct MAIN_BATTERY_PACK_PARAMS
{
public UInt16 wRemainingCapacity;
public UInt16 wCycleCount;
public UInt16 wTimeToFull;
public UInt16 wSerialNumber;
public UInt16 wRatedCapacity;
public UInt16 wActualCapacity;
public UInt16 wManufactureDate;
public UInt16 wBatteryStatus;

public System.Text.StringBuilder ManufactureName;
public System.Text.StringBuilder DeviceName;
public System.Text.StringBuilder DeviceChemistry;

}

Can anyone give me a hand with this one?

 

[Paul G. Tobey [eMVP]]

Check the actual DLL which supposedly implements the call and make sure that
it exports a function with *exactly* that name.

Paul T.

 

[BVayer]

We just double checked the header file to be certain and it is accurate.

 

[Paul G. Tobey [eMVP]]

The header file means close to nothing. If it was compiled with C++, the
actual exported name fo the function will *not* be what's in the header
file, but a mangled version indicating the parameter and return types of the
function, as well as that name.

Paul T.

 

[Ilya Tumanov [MS]]

Passing objects inside structures (StringBuilders in this case) is not
supported on NETCF V1, hence the exception.



Generic workaround:



For reference types: replace them with IntPtr fields, handle all memory
management (e.g. allocate unmanaged memory and copy data with Marshal class
or pin managed arrays with GCHandle class).



For nested types: declare byte array with size of structure, build structure
data inside array manually and pass this array to managed code.


--
Best regards,

Ilya

This posting is provided "AS IS" with no warranties, and confers no rights.

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[BVayer]

DWORD DiagBatGetBatteryPackParams( MAIN_BATTERY_PACK_PARAMS
lpBatPackInfo)

 

[Martin]

Hi,
I believe that the problem is in DIAG_BATTERY_STRINGS_T fields of the structure
try to pass IntPtr value to the function and after function succeed perform custom marshaling
to obtain all the values of the structure.

I am trying to P/Invoke a Motorola API and all I keep getting is the
NotSupportException.

The api uses a struct to manipulate the data and returns a DWORD
variable which I converted to uint.

The Struct is made up of several variables of type WORD and 3 variables
which are TCHAR of a fixed length. Those I have as strings; I also
tried them as StringBuilders. The variables which are of type WORD I
am converting to UInt16's.

The API:
typedef TCHAR DIAG_BATTERY_STRINGS_T [BATTERY_STRINGS_SIZE];

typedef struct tagMAIN_BATTERY_PACK_PARAMS
{
WORD wRemainingCapacity;
WORD wCycleCount;
WORD wTimeToFull;
WORD wSerialNumber;
WORD wRatedCapacity;
WORD wActualCapacity;
WORD wManufactureDate;
WORD wBatteryStatus;

DIAG_BATTERY_STRINGS_T ManufactureName;
DIAG_BATTERY_STRINGS_T DeviceName;
DIAG_BATTERY_STRINGS_T DeviceChemistry;

}


MY CODE:
[DllImport("DiagApi.dll")]
private static extern uint DiagBatGetBatteryPackParams( ref
MAIN_BATTERY_PACK_PARAMS MainBatteryInfo);

[StructLayout(LayoutKind.Sequential)]
public struct MAIN_BATTERY_PACK_PARAMS
{
public UInt16 wRemainingCapacity;
public UInt16 wCycleCount;
public UInt16 wTimeToFull;
public UInt16 wSerialNumber;
public UInt16 wRatedCapacity;
public UInt16 wActualCapacity;
public UInt16 wManufactureDate;
public UInt16 wBatteryStatus;

public System.Text.StringBuilder ManufactureName;
public System.Text.StringBuilder DeviceName;
public System.Text.StringBuilder DeviceChemistry;

}

Can anyone give me a hand with this one?

 

[BVayer]

I defined the Struct with IntPtr's rather than with the String or
Stringbuilder. This worked; I think. Well, I am retrieving all the
data now however I am throwing a Exception ( 0xC0000005 ) I looked up
the error and see it has to do with File Access. I read several of the
examples and threads too but, the solution to this issue is not clear
to me. Do I just need to set the IntPtr x = IntPtr.Zero prior to
passing it in as a parameter?

 

[Alex Feinman [MVP]]

If I understand correctly what your umnanaged structure looks like, these
are supposed to be embedded char arrays. You cannot use IntPtr for them.
Declare the whole thing as a byte array of a proper size (important!) and
then use BitConverter to access DWORDs and Encoding.GetString to access
strings

 

[BVayer]

Is this nessicary for CF2 as well? I was under the impression that CF2
would make my life alittle easier. If it is the case that I need to
change to the byte array .. could you pelase point me to a C# example.
Thank you.

 

[BVayer]

Is this nessicary for CF2 as well? I was under the impression that CF2
would make my life alittle easier. If it is the case that I need to
change to the byte array .. could you pelase point me to a C# example.
Thank you.

 

[Martin]

Well, you should not pass zero pointers (IntPtr)
because of DIAG_BATTERY_STRINGS_T [BATTERY_STRINGS_SIZE];
are arrays, I would allocate enought memroy for entire structure
and passed the pointer to this memory (as IntPtr pointer) to the function,
when after function returns I would unmarshal all the structure members.
I defined the Struct with IntPtr's rather than with the String or
Stringbuilder. This worked; I think. Well, I am retrieving all the
data now however I am throwing a Exception ( 0xC0000005 ) I looked up
the error and see it has to do with File Access. I read several of the
examples and threads too but, the solution to this issue is not clear
to me. Do I just need to set the IntPtr x = IntPtr.Zero prior to
passing it in as a parameter?

 

[Alex Feinman [MVP]]

In CF2 you can indeed:

[MarshalAs(UnmanagedType.ByValTStr, SizeConst=xxxx)]
string structMember;

 

[BVayer]

I tried to declare the struct with the lines you suggested and I was
able to successfully retrieve the struct. Thank you.