I am just a beginner in C++. I have errors with namespaces in Visual C++. Here is the code which include files I have to add for this foundation. The error says the name must be a namespace name. I add whole code is source folder. There is not single file in header. Wow many files do I have to add?
using namespace System;
int main()
{
if (Environment::HasShutdownStarted)
Console::WriteLine("Shutting down.");
else
Console::WriteLine("Not shutting down.");
return 0;
}
You should add this:
#using <mscorlib.dll>
If you want to use System namespace. Hope this helps.. :)
Try adding this:
#using <mscorlib.dll>
It is used to let the compiler know you are working with the system.
Related
My code starts off like this:
#include "stdafx.h"
#include <string>
#using <mscorlib.dll>
#using <System.Data.dll>
#using <System.dll>
using namespace System;
using namespace System::Data::OleDb;
but ends up with the compile error "#using" requires C++/CLI mode
I had this problem initially and managed to solve this through following this post IntelliSense: "#using" requires C++/CLI to be enabled. Updated VS2017 to ver 15.3.0 yesterday and now it is broken again. Project Properties are as follows:
Any assistance would be greatly appreciated.
P.
I came across the same issue and figured out that the settings(Common Language Runtime Support) were set only for Release configuration. I suggest you to check for all the configurations in your solutions Release/Debug etc.. and set the CLR support option and it should work as expected.
You can also control this setting from within the code by putting this in your files
#pragma managed
First I would search your code to be sure this #pragma isn't being used to turn OFF managed building somewhere earlier (in some #include file, perhaps?). Then try putting it in this file>
I'm not sure if this will solve your problem but it should at least eliminate the worry that the file is not being build properly. And perhaps the error message might change to give you a better idea what the problem is
https://msdn.microsoft.com/en-us/library/0adb9zxe.aspx?f=255&MSPPError=-2147217396
C++ CLI Correct way to use #pragma managed / unmanaged
So, I have this question. Why does cout throws
error C2065: 'cout' : undeclared identifier
I am using Visual Studio 2012 as an IDE and I am writing a school project. I have everything done except an example file. So I am trying to write something on the screen like this:
#include "iostream"
#include "stdafx.h"
using namespace std;
int main()
{
cout<<"example";
return 0;
}
So the problem is with cout... printf works fine, but I want to use cout.
EDIT:
I've changed "" to <> but it is not helping. Also I am using this code only for example... This is not the whole project.
stdafx.h shall be the first include directive in your source file.
Switch files and convert the second include to <>, as other suggested.
#include "stdafx.h"
#include <iostream>
See this post for more information.
First of all:
#include <iostream>
instead of #include "iostream"
Secondly, it is generally considered bad practice to write using namespace std;, even though most courses start with that. It is better to only use what you actually need, in your case:
using std::cout;
#include "iostream"
should be
#include <iostream>
Quoting from this post:difference-between-iostream-and-iostream-quotes-in-include
By courtesy of #Jerry Coffin's answer:
When you use < >, the compiler only looks in the system-designated directory/directories (e.g., whatever you've set in the include environment variable) for the header.
When you use " ", the compiler looks in the local directory first, and if that fails, re-searches just like you'd used < >. Technically, (i.e., according to the standard) that doesn't have to be the "local" directory, but that's how it works in essentially every compiler of which I'm aware).
EDIT:
However, the root cause is that stdafx.h is a precompiled header. Visual C++ will not compile anything before the #include "stdafx.h" in the source file, unless the compile option /Yu'stdafx.h' is unchecked (by default); it assumes all code in the source up to and including that line is already compiled. However, it is still better to use <> with iostream not to confuse reader of the code.
If you use #include <iostream> with the <> instead of "" then it should work. Right now, the compiler doesn't know where to find the iostream library.
Also, you might want to change cout<<"example"; to cout<<"example"<<endl; for a new line so that it formats correctly.
Came across this issue while trying to build a Dynamic Linked Library. Make sure that instead of the #include stdafx.h you specify the following include on the first line of your .cpp file:
#include "pch.h"
This should also be the case for VS2017 or earlier.
This error also occurred in the Visual Studio 2017 IDE. Moving stdafx.h to the top solved the error.
For more on stdafx.h, see What's the use for "stdafx.h" in Visual Studio?
I am new to C++. I just started! I tried a code on Visual C++ 2010 Express version, but I got the following code error message.
------ Build started: Project: abc, Configuration: Debug Win32 ------
ugo.cpp
c:\users\castle\documents\visual studio 2010\projects\abc\abc\ugo.cpp(3): fatal error C1083: Cannot open include file: 'iostream': No such file or directory
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
This is the code:
// first.cpp -- displays a message
#include <iostream> // A PREPROCESSOR directive
int main(void) // Function header
{ // Start of a function body
using namespace std;
cout << "Come up and C++ me sometime.\n"; // Message
// Start a new line
cout << "Here is the total: 1000.00\n";
cout << "Here we go!\n";
return 0;
}
Replace
#include <iostream.h>
with
using namespace std;
#include <iostream>
Some things that you should check:
Check the include folder in your version of Visual Studio (in "C:\Program Files\Microsoft Visual Studio xx.x\VC\include", check for the file which you are including, iostream, make sure it's there).
Check your projects Include Directories in <Project Name> → Properties → Configuration Properties → VC++ Directories → Include Directories (it should look like this: $(VCInstallDir)include;$(VCInstallDir)atlmfc\include;$(WindowsSdkDir)include;$(FrameworkSDKDir)\include;)
Make sure that you selected the correct project for this code
(menu File → New → Project → Visual C++ → Win32 Console Application)
Make sure that you don't have <iostream.h> anywhere in your code files, Visual Studio doesn't support that (in the same project, check your other code files, .cpp and .h files for <iostream.h> and remove it).
Make sure that you don't have more than one main() function in your project code files (*in the same project, check your other code files, .cpp and .h files for the* main()` function and remove it or replace it with another name).
Some things you could try building with:
Exclude using namespace std; from your main() function and put it after the include directive.
Use std::cout without using namespace std;.
I had this exact same problem in Visual Studio 2015. It looks like as of Visual Studio 2010 and later you need to include #include "stdafx.h" in all your projects.
#include "stdafx.h"
#include <iostream>
using namespace std;
The above worked for me. The below did not:
#include <iostream>
using namespace std;
This also failed:
#include <iostream>
using namespace std;
#include "stdafx.h"
You are more than likely missing $(IncludePath) within Properties → VC++ Directories → Include Directories.
Adding this should make iostream and others visible again. You probably deleted it by mistake while setting up your program.
If your include directories are referenced correctly in the VC++ project property sheet → Configuration Properties → VC++ directories → Include directories, the path is referenced in the macro $(VC_IncludePath).
In my Visual Studio 2015 this evaluates to:
"C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include"
using namespace std;
#include <iostream>
That did it for me.
It is possible that your compiler and the resources installed around it were somehow incomplete. I recommend re-installing your compiler: it should work after that.
I got this error when I created an 'Empty' console application in Visual Studio 2015. I recreated the application, leaving the 'Empty' box unchecked. It added all of the necessary libraries.
Make sure you have Desktop Development with C++ installed.
I was experiencing the same problem, because I only had Universal Windows Platform Development installed.
Microsoft Visual Studio is funny. When you're using the installer, you must checkbox a lot of options to bypass the .NET framework (somewhat) to make more C++ instead of C# applications, such as the CLR options under desktop development... in the Visual Studio installer.... the difference is the C++ Win32 console project or a C++ CLR console project.
So what’s the difference? Well, I'm not going to list all of the files CLR includes, but since most good C++ kernels are in Linux... So CLR allows you to bypass a lot of the Windows .NET framework because Visual Studio was really meant for you to make applications in C#.
Here’s a C++ Win32 console project!
#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
cout << "Hello, World!" << endl;
return 0;
}
Now here’s a C++ CLR console project!
#include "stdafx.h"
using namespace System;
int main(array<System::String ^> ^args)
{
Console::WriteLine("Hello, World!");
return 0;
}
Both programs do the same thing .... the CLR just looks more frameworked class overloading methodology, so Microsoft can great its own vast library you should familiarize yourself with if so inclined.
Keywords (C++)
Other things you'll learn from debugging to add for error avoidance:
#ifdef _MRC_VER
#define _CRT_SECURE_NO_WARNINGS
#endif
If you created an environment variable with the name IncludePath, try renaming it to something else.
This name will override $(IncludePath) inside project properties.
Quick fix for small programs:
Add: #include <cstdlib>
In my case, my Visual Studio 2015 installed without selecting C++ package, and Visual Studio 2017 is installed with the C++ package. If I use Visual Studio 2015, opening a C++ project will show this error, and using Visual Studio 2017 will be no error.
I had this problem too. I used this code (before main();) in Visual Studio 2022, and it turned OK:
#include "pch.h"
#include <iostream>
using namespace std;
using namespace winrt;
using namespace Windows::Foundation;
In my case, the error occurred when I created a file in VS Code, without giving the .cpp extension. It resolved when I renamed it with the .cpp.
// first.cpp -- displays a message
#include <iostream> // a PREPROCESSOR directive
using namesapce std;
int main() // function header
{ // start of a function body
///using namespace std;
cout << "Come up and C++ me sometime.\n"; // message
// start a new line
cout << "Here is the total: 1000.00\n";
cout << "Here we go!\n";
return 0;
}
i am getting this error which i unable to remove in visual studio 2010. i am using one third party library which uses its own definition for "string" Also visual studio's xstring file is there in the folder where it gets installed. now when i am trying to compile code i am getting following error
1>...\xyz.cpp(24): error C2872: 'string' : ambiguous symbol
1> could be 'third party library path\string.h(31)
1> or 'c:\program files (x86)\microsoft visual studio 10.0\vc\include\xstring(2063) : std::string'
compiler is not able to understand which string definition it should use. How can i remove this error in visual studi 2010. I want the code to use third party string definition.
i tried to set third party path in include directory but still i am seeing this error.
Please help me. Thanks in advance
This is an example of a namespace clash. You probably have in your code:
#include <3rdPartyString.h> // declaration of 3rd party string type
#include <string> // declaration of std::string
using namespace 3rdPartyNamespace;
using namespace std;
...
string myStr; // which string type?
Compiler now doesn't know which string you want to use - one from 3rd party library or STL one. You can resolve this ambiguity by prepending namespace name to the type:
3rdPartyNamespace::string myStr; // if you want to use string from 3rd party library
or
std::string myStr; // if you want to use STL string
Never place using namespace namespace_name; in headers but try to avoid it in source files as well. The best practice is to prepend type name as this does doesn't pollute your current namespace with the other one thus avoiding namespace clashes.
Namespaces were invented to prevent these ambiguities. Make sure you never use using namespace std (that specific using namespace is bad practice anyway, and "std::" isn't that long to type) and it should be fine, just use std::string if you want the standard string.
// Without "using namespace std;"
string foo; // string from third party library used.
std::string bar; // string from standard library used.
The two definitions of string are clashing with each other so the compiler doesn't know what to use so you need a way to differentiate the two and that's where namespaces come in.
You can use the namespace that your third party string uses when referring to that string as the errors you are showing implies you have using namespace std in your code.
I ran into this issue recently by adding a Class Library project to a very large solution that included an in-house String library, the using namespace System; in the pre-generated header was causing the ambiguity.
There is System.String. If not intended to use, make sure to indicate otherwise. Example System::String, or Custom::String
I want to use Directory.GetFiles to read files from a folder. From msdn website i found:
For c, i have include:
using System;
using System.IO;
For C++, i have include:
#using <mscorlib.dll>
using namespace System;
using namespace System::IO;
as header.
For the C++, after the line #using is added, the "fatal error C1190: managed targeted code requires a '/clr' option" appears. So i tried by adding /clr in the visual studio Properties\Linker\Command Line as i found it in other website, but i fail too.
I did it wrongly. So, How to handle error of "fatal error C1190: managed targeted code requires a '/clr' option"? How to "compile with the /clr flag"?
Because i am writing for OpenCv, i have include the following additional dependencies in order to use c and c++:
cv210d.lib
cxcore210d.lib
highgui210d.lib
cvaux210d.lib
Cannot work. What other requirements in order to use Directory.GetFiles?
I also cannot use foreach even i #include .
Is there something similar to use foreach and Directory.GetFiles which is necessary to be included in a project?
I am using Visual Studio 2008
Please help me. Tq
You need to create managed c++ CLI, this should include all the flags for you.
To set /clr from visual studio, go to porject properities->configurations properities->general set common language runtime support to /clr