Handling exceptions for winrt::hresult

Question

Handling exceptions for winrt::hresult

Noah Aas 925

Hello,

Dialog -- Object -- MyTest

If I have an exception I need to go inside there ########

void CMFCCopyDataDlg::RequestPanelIn(CString data)
{
try
{
CurrentPanel.SetPanelInfos(data);
}
catch (exception ex)
{

}
catch (char* errorMessage)
{
// Inside ######## triggered by function below
CString errorfrom(errorMessage);


// -------------------------------------------------------

Not working, why?

void MyTest::SetPanelInfos(CString data)
{
if (JsonObject::TryParse(jsonstr, obj))
{
try
{
MessageId = obj.GetNamedString(L"MessageId").c_str();
Station = obj.GetNamedString(L"Station").c_str();

Program = obj.GetNamedString(L"Program").c_str();
Order = obj.GetNamedString(L"Order").c_str();
Referencecode = obj.GetNamedString(L"Re ferencecode").c_str();

OrderQuantity = obj.GetNamedNumber(L"OrderQuantity");
OrderQuantityCurrent = obj.GetNamedNumber(L"OrderQuantityCurrent");
OrderQuantityGood = obj.GetNamedNumber(L"OrderQuantityGood");
OrderQuantityBad = obj.GetNamedNumber(L"OrderQuantityBad");
}
catch (winrt::hresult_error const& ex)
{
winrt::hresult hr = ex.code(); // HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND).
winrt::hstring message = ex.message(); // The system cannot find the file specified.


hstring jsonstrError = winrt::to_hstring(message);

std::string tempStr(message.begin(), message.end());
CString sError = tempStr.c_str();
sError.Format("Error;%s", sError);

string error = "Error;" + tempStr;
throw error;

If I write this, works (not as string variable)

catch (winrt::hresult_error const& ex)
{
winrt::hresult hr = ex.code(); // HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND).
winrt::hstring message = ex.message(); // The system cannot find the file specified.
throw "Error- TEST;

Then I can get in there.

But I need the whole message. The best with Error number and Error message.

RLWA32 48,151 Reputation points

2025-03-27T18:11:07.3466667+00:00

Why use an inner try/catch to convert winrt::hresult_error to something else?

Consider catching that exception in the outer try/catch.
Darran Rowe 1,541 Reputation points

2025-03-27T19:44:21.4466667+00:00

I have to ask. Why not use HasKey? If you are invested in using the GetNamedXXX, why not use the second overload?

What I mean by this is GetNamedString has two overloads, there is GetNamedString with a single string parameter, and then there is GetNamedString with two string parameters. This second overload doesn't throw. It will instead return the value you provided as the second parameter to indicate that the value was not found.

The rest of the GetNamedXXX members have a similar second overload, so there is a way to easily detect that the value is missing without having to deal with exceptions.

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RLWA32 48,151 Reputation points

2025-03-27T18:11:07.3466667+00:00

Why use an inner try/catch to convert winrt::hresult_error to something else?

Consider catching that exception in the outer try/catch.
Darran Rowe 1,541 Reputation points

2025-03-27T19:44:21.4466667+00:00

I have to ask. Why not use HasKey? If you are invested in using the GetNamedXXX, why not use the second overload?

What I mean by this is GetNamedString has two overloads, there is GetNamedString with a single string parameter, and then there is GetNamedString with two string parameters. This second overload doesn't throw. It will instead return the value you provided as the second parameter to indicate that the value was not found.

The rest of the GetNamedXXX members have a similar second overload, so there is a way to easily detect that the value is missing without having to deal with exceptions.

Answer 1

Minxin Yu 13,501 Microsoft External Staff

Hi,

winrt::hresult_error

 catch (winrt::hresult_error const& ex)
    {
        winrt::hresult hr = ex.code (); // HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND).
        winrt::hstring message = ex.message (); // The system cannot find the file specified.
        throw winrt::hresult_error (hr, message);
    }

As Darran Rowe said, there are HasKey and

GetNamedString(String, String)

Gets the String value with the specified name, or the provided default value if no such named value is found.

So throwing an exception is not needed.

Best regards,

Minxin Yu

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Noah Aas 925

Thanks, I can make it via the outside try catch.

catch (winrt::hresult_error const& ex)
{
    winrt::hresult hr = ex.code(); // HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND).

https://learn.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/error-handling

How can I read out the code? ex.code() How do I get into the other exceptions?

void CMFCDataDlg::RequestPanel(CString data)
{
	try
	{
		CurrentPanelInReqMachine.SetPanelReq(data);
	}
	catch (winrt::hresult_error const& ex)
	{
	// is ok coming in
		winrt::hresult hr = ex.code(); // HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND).
		winrt::hstring message = ex.message(); // The system cannot find the file specified.

		hstring jsonstrError = winrt::to_hstring(message);
		std::string tempStr(message.begin(), message.end());
		CString errorMessage = tempStr.c_str();
	}
	catch (exception ex)
	{
	// is ok coming in   is calling from throw std::runtime_error("Failed to parse JSON.");
		CString help(ex.what());
		CString errorMessage;
		errorMessage.Format("Error;%s", (LPCSTR)help);	
	}
	catch (char* errorMessage)
	{
	// When is this exception called?
		CString errorfrom(errorMessage);
		if (errorfrom.MakeLower() == "higher-level system")
		{
		}
	}
	catch (std::invalid_argument const& ex)
	{
	// When is this exception called?
		CString exception = ex.what();
	}
}

Darran Rowe 1,541 Reputation points

2025-03-29T12:39:05.5666667+00:00
Catch blocks don't have fall through. They also follow scope very strictly.

#include <stdexcept> #include <cstdio> void protected_fun() { throw std::runtime_error("Error"); } void protected_except_fun() { throw std::exception("Error"); } void protected_main() { try { protected_fun(); } catch (const std::runtime_error &re) { protected_except_fun(); } catch (const std::exception &e) { //This is never touched. } catch (...) { } } int wmain() { bool outer_except = false; try { protected_main(); } catch (...) { //The exception thrown by protected_except_fun will //be caught by this block. outer_except = true; } if(outer_except) { wprintf(L"The catch all handler in wmain caught an exception.\n"); } return 0; }

It is only statements inside a try block that will get caught by the catch block associated with that try block. The above illustrates this. Even if another catch block associated with the try handles the exception. If a handler is thrown in a catch block, then it will be handled by the exception handler in the next scope out.

Even if you put this throw inside a try block and rethrow, the exception handling code will first look for what try block it is handled by, and then only use catch blocks associated with that try block. In other words, try is a one shot deal.
Noah Aas 925 Reputation points

2025-03-31T16:39:07.2033333+00:00

Thanks for your help!

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Handling exceptions for winrt::hresult

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