I've run into this problem before, but never in a situation like this. I'm completely confused. As the question states, I'm getting the runtime error "Object reference not set to an instance of an object." Using the debugger tools, I think I've pinpointed the problem to this line:
dataFileLocation = path;
The entire function is here:
void DATReader::SetPath(String^ path)
{
if(!File::Exists(path))
{
MessageBox::Show( "DATReader (missing dat file: \n"+path+"\n )", "Error", MessageBoxButtons::OK, MessageBoxIcon::Exclamation);
return;
}
dataFileLocation = path;
}
dataFileLocation is declared here, but nothing is assigned to it:
ref class DATReader
{
private:
System::String^ dataFileLocation;
// ...
}
Now I know the reason I'm getting the error is because dataFileLocation is assigned to nothing. But I'm having problems assigning it. When I add = 0; to it, it won't build because its a ref class. When I try to assigned it to = 0; in the constructor, it yells at me for trying to convert it from a System::String^ to an int. If I assign it to a = gcnew String(""); it builds, but throws the same runtime exception.
I don't get it, am I reading the debugger wrong, and this isn't the source of the problem at all? I've just started to use managed code recently, so I'm confused :\
You may want to check and make sure your DATReader object isn't null as well It may be throwing the exception at your DATReader.SetPath() call.
This is a nicety in C# that's missing in C++/CLI. C# generates code that ensures this can never be null. Easily seen in the debugger by setting a breakpoint on the method and inspecting "this". Here's an example program that reproduces the exception:
#include "stdafx.h"
using namespace System;
ref class Example {
String^ dataFileLocation;
public:
void SetPath(String^ path) {
dataFileLocation = path; // Set breakpoint here and inspect "this"
}
};
int main(array<System::String ^> ^args)
{
Example^ obj /* = gcnew Example */;
obj->SetPath("foo");
return 0;
}
Remove the /* */ comments to fix. Fix your code by looking at the call stack to find the method that forgot to instantiate the object.
Managed C++ uses nullptr for null references. So you can check:
if (path == nullptr) { ... }
or use:
if (!String::IsNullOrEmpty(path))
Related
I'm trying to figure out why at this point in the code I'm getting an E_INVALIDARG hresult:
// main.cpp
class App : public implements<App, IFrameworkView>
{
// stuff ...
};
class AppFactory : public implements<AppFactory, IFrameworkViewSource>
{
public:
IFrameworkView CreateView()
{
return make<App>();
}
};
int WINAPI wWinMain(
_In_ HINSTANCE,
_In_ HINSTANCE,
_In_ LPWSTR,
_In_ int)
{
init_apartment();
auto vpf = make<AppFactory>();
CoreApplication::Run(vpf); // <-- throwing E_INVALIDARG somewhere inside CoreApplication::Run
uninit_apartment();
return S_OK;
}
I'd have expected a compile error if I didn't do something required by a class inheriting implements<AppFractory, IFrameworkViewSource>, but as far as I know I'm checking (static) boxes.
fwiw the exception is triggered here:
// Windows.ApplicationModel.Core.h
template <typename D> auto consume_Windows_ApplicationModel_Core_ICoreApplication<D>::Run(winrt::Windows::ApplicationModel::Core::IFrameworkViewSource const& viewSource) const
{
check_hresult(WINRT_IMPL_SHIM(winrt::Windows::ApplicationModel::Core::ICoreApplication)->Run(*(void**)(&viewSource)));
}
The thing inside check_result(...) is what's returning E_INVALIDARG, and subsequently triggering the exception. I'm not a super expert at writing windows applications, largely still in the "copy the template and hope it works while trying to understand something" phase. If there's some kind of tool I should be using to understand what the actual argument I'm passing is that is invalid, I'd appreciate some kind of pointer. I would think if I'm not passing the correct thing here, the strong type check of the argument would trigger a compile error and I'd have an opportunity to address the issue.
Honestly I'm lost here, would appreciate a hint towards where to look to resolve my issue. Thank you.
Update:
Don't know if this is relevant but in the Output tab in VS a line prints out:
Exception thrown at 0x00007FFA6D9A4FD9 (KernelBase.dll) in MyProgram.exe: WinRT originate error - 0x80070057 : 'serverName'.
I have no idea what this is... "serverName"? I don't even see a mention of this in the CoreApplication::Run docs.
So I looked into some tutorials for DirectX12 and when I copied the code that I downloaded from here it worked but when I brought them into a class and wanted to use it, it just crashes in UpdateRenderTargetView method at the m_BackBuffers[i] = backBuffer;
It says:
Exception thrown at 0x00007FF831C65FA1 (d3d10warp.dll) in Hazelnut.exe: 0xC0000005: Access violation writing location
The Code:
void D3D12Core::UpdateRenderTargetViews(ComPtr<IDXGISwapChain4> swapChain, ComPtr<ID3D12DescriptorHeap> descriptorHeap)
{
auto rtvDescriptorSize = m_Device->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
CD3DX12_CPU_DESCRIPTOR_HANDLE rtvHandle(descriptorHeap->GetCPUDescriptorHandleForHeapStart());
for (int i = 0; i < m_BufferCount; ++i)
{
ComPtr<ID3D12Resource> BackBuffer;
swapChain->GetBuffer(i, IID_PPV_ARGS(&BackBuffer));
m_Device->CreateRenderTargetView(BackBuffer.Get(), nullptr, rtvHandle);
m_BackBuffers[i] = BackBuffer;
rtvHandle.Offset(rtvDescriptorSize);
}
}
Class members That I used in function:
class D3D12Core
{
public:
//Some members
static const uint8_t m_BufferCount = 3;
ComPtr<ID3D12Resource> m_BackBuffers[m_BufferCount];
private:
ComPtr<ID3D12Device2> m_Device;
//Some members
};
I tried everything that I could but didn't find the cause.
Normally it shouldn't crash at all.
Please be gentle.I'm new to Stackoverflow.
Any help will be appreciated.
Edit:
D3D12Core
D3D12Core Implementation
And I use it like this:
auto commnadQueue = D3D12Core::Get().GetCommandQueue(D3D12_COMMAND_LIST_TYPE_DIRECT);
m_SwapChain = D3D12Core::Get().CreateSwapChain(m_WindowHandle, commnadQueue->GetD3D12CommandQueue(), m_Width, m_Height);
m_RTVDescriptorHeap = D3D12Core::Get().CreateDescriptorHeap(1, D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
D3D12Core::Get().UpdateRenderTargetViews(m_SwapChain, m_RTVDescriptorHeap);
the UpdateRenderTargetViews function will get call by another function in window class that will be used for WndProc.
I didn't write in which class or file this written I don't think it will be necessary.
Well after you provided some more source code, I am pretty sure the mistake is here:
m_RTVDescriptorHeap = D3D12Core::Get().CreateDescriptorHeap(1, D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
which should actually be
m_RTVDescriptorHeap = D3D12Core::Get().CreateDescriptorHeap(D3D12Core::m_BufferCount, D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
You are offseting the handle in a for loop which goes out of bounds in second iteration.
Actually i am working on c++/CLI dll which is using C# dll and c++/cli dll will use from native c.
c++/cli code is like:-
public ref class Class1
{
// TODO: Add your methods for this class here.
public:
static Managed_EMV_DLL::Managed_EMV ^obj = gcnew Managed_EMV(); // object of c# class
bool INIT_READER(unsigned int *);
bool READ_KEY(unsigned int *ERROR_CODE,unsigned char *RETURN_ARRAY, unsigned int *Array_LENGTH);
};
-i want to handle the exception in c++/CLI code,
-handle exception when c# dll not found.
how i can make it.
What is the exact problem you're facing .... See the below example format.
try
{
}
catch(FormatException ^) // display an appropriate message
{
Console::WriteLine(L"You must enter a valid number "
L"and no other character!");
}
Just sort out what exception could be thrown from C# dll and then put appropriate handles in your C++/CLI code.
I want to handle any kind of exception not only FormatException or TypeInitializationException.
Here i write code like:-
try
{
}
catch (Exception^ ex)
{
Console::WriteLine("Error in C++/CLI INIT function: {0}", ex->ToString());
}
catch (...)
{
Console::WriteLine("Error in INIT");
}
and it works good.... i hope it will catch any kind of exception...
I'm trying to give a short example of IDynamicMetaObjectProvider for the second edition of C# in Depth, and I'm running into issues.
I want to be able to express a void call, and I'm failing. I'm sure it's possible, because if I dynamically call a void method using the reflection binder, all is fine. Here's a short but complete example:
using System;
using System.Dynamic;
using System.Linq.Expressions;
class DynamicDemo : IDynamicMetaObjectProvider
{
public DynamicMetaObject GetMetaObject(Expression expression)
{
return new MetaDemo(expression, this);
}
public void TestMethod(string name)
{
Console.WriteLine(name);
}
}
class MetaDemo : DynamicMetaObject
{
internal MetaDemo(Expression expression, DynamicDemo demo)
: base(expression, BindingRestrictions.Empty, demo)
{
}
public override DynamicMetaObject BindInvokeMember
(InvokeMemberBinder binder, DynamicMetaObject[] args)
{
Expression self = this.Expression;
Expression target = Expression.Call
(Expression.Convert(self, typeof(DynamicDemo)),
typeof(DynamicDemo).GetMethod("TestMethod"),
Expression.Constant(binder.Name));
var restrictions = BindingRestrictions.GetTypeRestriction
(self, typeof(DynamicDemo));
return new DynamicMetaObject(target, restrictions);
}
}
class Test
{
public void Foo()
{
}
static void Main()
{
dynamic x = new Test();
x.Foo(); // Works fine!
x = new DynamicDemo();
x.Foo(); // Throws
}
}
This throws an exception:
Unhandled Exception:
System.InvalidCastException: The
result type 'System.Void' of the
dynamic binding produced by the object
with type 'DynamicDemo' for the binder
'Microsoft.CSharp.RuntimeBinder.CSharpInvokeMemberBinder'
is not compatible with the result type 'System.Object' expected by the
call site.
If I change the method to return object and return null, it works fine... but I don't want the result to be null, I want it to be void. That works fine for the reflection binder (see the first call in Main) but it fails for my dynamic object. I want it to work like the reflection binder - it's fine to call the method, so long as you don't try to use the result.
Have I missed a particular kind of expression I can use as the target?
This is similar to:
DLR return type
You do need to match the return type specified by the ReturnType property. For all of the standard binaries this is fixed to object for almost everything or void (for the deletion operations). If you know you're making a void call I'd suggest wrapping it in:
Expression.Block(
call,
Expression.Default(typeof(object))
);
The DLR used to be quite lax about what it would allow and it would provide some minimal amount of coercion automatically. We got rid of that because we didn't want to provide a set of convensions which may or may not have made sense for each language.
It sounds like you want to prevent:
dynamic x = obj.SomeMember();
There's no way to do that, there'll always be a value returned that the user can attempt to continue to interact with dynamically.
I don't like this, but it seems to work; the real problem seems to be the binder.ReturnType coming in oddly (and not being dropped ("pop") automatically), but:
if (target.Type != binder.ReturnType) {
if (target.Type == typeof(void)) {
target = Expression.Block(target, Expression.Default(binder.ReturnType));
} else if (binder.ReturnType == typeof(void)) {
target = Expression.Block(target, Expression.Empty());
} else {
target = Expression.Convert(target, binder.ReturnType);
}
}
return new DynamicMetaObject(target, restrictions);
Perhaps the callsite expects null to be returned but discards the result - This enum looks interesting, particularly the "ResultDiscarded" flag...
[Flags, EditorBrowsable(EditorBrowsableState.Never)]
public enum CSharpBinderFlags
{
BinaryOperationLogical = 8,
CheckedContext = 1,
ConvertArrayIndex = 0x20,
ConvertExplicit = 0x10,
InvokeSimpleName = 2,
InvokeSpecialName = 4,
None = 0,
ResultDiscarded = 0x100,
ResultIndexed = 0x40,
ValueFromCompoundAssignment = 0x80
}
Food for thought...
UPDATE:
More hints can be gleaned from Microsoft / CSharp / RuntimeBinder / DynamicMetaObjectProviderDebugView which is used (I presume) as a visualizer for debuggers. The method TryEvalMethodVarArgs examines the delegate and creates a binder with the result discarded flag (???)
Type delegateType = Expression.GetDelegateType(list.ToArray());
if (string.IsNullOrEmpty(name))
{
binder = new CSharpInvokeBinder(CSharpCallFlags.ResultDiscarded, AccessibilityContext, list2.ToArray());
}
else
{
binder = new CSharpInvokeMemberBinder(CSharpCallFlags.ResultDiscarded, name, AccessibilityContext, types, list2.ToArray());
}
CallSite site = CallSite.Create(delegateType, binder);
... I'm at the end of my Reflector-foo here, but the framing of this code seems a bit odd since the TryEvalMethodVarArgs method itself expects an object as a return type, and the final line returns the result of the dynamic invoke. I'm probably barking up the wrong [expression] tree.
-Oisin
The C# binder (in Microsoft.CSharp.dll) knows whether or not the result is used; as x0n (+1) says, it keeps track of it in a flag. Unfortunately, the flag is buried inside a CSharpInvokeMemberBinder instance, which is a private type.
It looks like the C# binding mechanism uses ICSharpInvokeOrInvokeMemberBinder.ResultDiscarded (a property on an internal interface) to read it out; CSharpInvokeMemberBinder implements the interface (and property). The job appears to be done in Microsoft.CSharp.RuntimeBinder.BinderHelper.ConvertResult(). That method has code that throws if the aforementioned ResultDiscarded property doesn't return true if the type of the expression is void.
So it doesn't look to me like there's an easy way to tease out the fact that the result of the expression is dropped from the C# binder, in Beta 2 at least.
i have got a ScreenCameraSDK and it comes with a 11kb dll file, it has a documentation too which lists the functions which can be used. It says
ScreenCamera SDK ActiveX Reference Documentation
ActiveX Reference
The ActiveX ID on the system is: ScreenCameraSDK.RemoteControl
Every method on the interface returns FAIL or SUCCESS. (0 or 1).
Create an instance of the ActiveX on your application, and then call InitializeScreenCameraRemoteControl. If the return value is SUCCESS then ScreenCamera is properly installed and you can then call any other method on the ActiveX's interface. If not ScreenCamera could not be found and you should contact support.**
Now my question is, i have the dll and no other files. How can i use the functions inside it in a VC++ Project with Visual Studio 2008.
Thanks
I TRIED THE FOLLOWING CODE BUT GOT COMPILATION ERROR OF UNDEFINED IDENTIFIER
#include <stdio.h>
// This is the path for your DLL.
// Make sure that you specify the exact path.
#import "e:\ScreenCameraSDK.dll" no_namespace
void main()
{
BSTR bstrDesc;
try
{
CoInitialize(NULL);
short st = 2;
short st1;
// Declare the Interface Pointer for your Visual Basic object. Here,
// _Class1Ptr is the Smart pointer wrapper class representing the
// default interface of the Visual Basic object.
_Class1Ptr ptr;
// Create an instance of your Visual Basic object, here
// __uuidof(Class1) gets the CLSID of your Visual Basic object.
ptr.CreateInstance(__uuidof(Class1));
st1 = ptr->MyVBFunction(&st);
}
catch(_com_error &e)
{
bstrDesc = e.Description();
}
CoUninitialize();
}
it says _Class1Ptr is unknown!
BSTR bstrDesc;
try
{
HRESULT hr= CoInitialize(NULL);
CLSID clsid;
hr = CLSIDFromProgID(OLESTR("<complete class name as see in registry>"),&clsid);
short st = 2;
short st1;
//nameOfClassInOCX is placeholder for explanation. If you OCX com class name is blabla
//use _blabla and so on.
_nameOfClassInOCX * ptr;
hr = CoCreateInstance(clsid,NULL,CLSCTX_INPROC_SERVER,__uuidof(_nameOfClassInOCX ),(LPVOID*)&ptr);
cout << ptr->GetFees("hi") <<endl;
ptr->Release();
}
catch(_com_error &e)
{
bstrDesc = e.Description();
}
CoUninitialize();
First of all you have to do this is #import the dll, and the compiler will automatically generate all required definitions from it. Then create objects from the library by using either smart pointers, or CreateInstance().
#import "C:\files\test.dll" no_namespace rename("EOF", "EOFile")
...
int main() {
if (FAILED(::CoInitialize(NULL)))
return 0;
........
::CoUninitialize();
return 0;
}