Is there any way I can emulate C++ value template parameters in C#?
template<bool flag>
void Method()
{
// Do some work
if constexpr(flag)
{
// Do something specific
}
// Do some more work
}
So that it would generate two versions of a method which can be called like this:
Method<false>();
Method<true>();
This is for performance reasons, so it is better to not make additional calls inside the Method. The Method is performance critical part and it is called billions of times so it is important to squeeze every CPU cycle from it.
On the other hand it has a rather complicated logic, so I would prefer to not have two copies of it.
I think I could do something with generics, but it wouldn't be the best option for performance. So now the only way I can think of is to create some kind of template code generator for it. But maybe there are other options?
Maybe it is possible to compile two versions of the method using Roslyn, so that it would create two optimized versions of it with specific arguments?
void Method(bool flag)
{
// Do some work
if (flag)
{
// Do something specific
}
// Do some more work
}
So that I can compile it to:
void Method_false(false)
{
// Do some work
// Do some more work
}
and to:
void Method_true(true)
{
// Do some work
// Do something specific
// Do some more work
}
Is it at all possible?
Metaprogramming is not possible in C#. Look for possible alternatives in the form of code transformation tools in the following SO question: Is metaprogramming possible in C#?
You can't do this from language directly, however it is possible because JIT is smart enough. Create an interface and two structs:
public interface IBool
{
bool IsTrue();
}
public struct True : IBool
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public bool IsTrue()
{
return true;
}
}
public struct False : IBool
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public bool IsTrue()
{
return false;
}
}
Please note that implementations of IsTrue are marked with MethodImpl attribute. Now rewrite your Method as generic:
public static void Method<T>(ref T flag) where T : struct, IBool
{
if (flag.IsTrue())
{
Console.WriteLine(42);
}
else
{
Console.WriteLine(24);
}
}
There is important thing: T has struct constraint so JIT aware that there is no inherited types from T and nobody can override return value of IsTrue. Also, because this method will be inlined, JIT replace call to IsTrue with constant. And when you have
if (false)
{
// some code
}
that means that whole code block will be removed. As a result JIT will create two implementations of Method: first with content of if section and seconf with content of else section. You can check this in disassembly window:
This question already has answers here:
How to stop evaluation of parameters in calls to debug functions when in Release build (C#)
(3 answers)
Closed 4 years ago.
Please note that I am aware of Debug.Print - the Console.WriteLine is a very simplified example of what I'm trying to do.
Is there a way to have a single line of code which exists only in Debug mode, which does not appear in Release at all?
I have some commands which help me debug the execution of a performance-critical section of code, and I have placed a large number of them all over the function in key places.
Here is an example of what I've done:
using System;
public class C {
public Object _obj = new object();
public void M()
{
Alpha("This goes away in Release");
Alpha(_obj.GetHashCode() + "...but this doesn't");
#if DEBUG
//But I don't want this three line deal.
Alpha(_obj.GetHashCode() + "...of course this does get removed");
#endif
}
public static void Alpha(String s)
{
#if DEBUG
Console.WriteLine(s);
#endif
}
}
The issue is that in release mode, the compiler recognizes that the first call does nothing in release mode, and removes it. But it does not do that in the second call. I know this because I have tested it in SharpLab: https://sharplab.io/#v2:EYLgHgbALANALiAhgZwLYB8CQBXZBLAOwHMACAZQE9k4BTVAbgFgAoTAB22ABs8BjE3lxTISAYRIBvFpnace/APLAAVjV5wSAfQD2KkgF4SBGgHcSu1eoAUASiatZ3PiQBu2vABMSAWVslpmFIOmACCXGwAFohWAEQAKhF4IkTaNCKIJogUJIQkAEo0XDQoNDF2AaHhUVY6KgB0AOI0cAASKBGi2h40fgDUJDF1Q8DYGnCJIh6pyAQAAgC0AIxwZfYymBUAxHgAZiQAIgCiAEIAqg3+wZgA9NfHoyQAkiRTc0samQRjEyTjAE40GgkHjGF7FLh1CqVSLRWrKRrNNrIDpdHo2Ej9QZDbR7XjabB/ZBA8ZJF7TEhEZokAGobQuGgeVZbGgEDy7KEBAC+AQCHCc/GoiDgzjcnhIYRhVjIcD+hFIyBsASC622eyOZwaUM6BGQ2iKdQA6rLaAAZQg9BVrGSbFlsnZc6ScoA==
Is there any way of avoiding the three-line version?
Yes, just put a [Conditional(...)] attribute on the method that you need to "not exist" unless you are using the Debug configuration:
[System.Diagnostics.Conditional("DEBUG")]
public static void Alpha(String s)
{
Console.WriteLine(s);
}
All calls to such methods are effectively removed (not compiled) unless the specified symbol is present.
Note that a restriction applies: [Conditional(...)] can only be used for void methods.
You probably desire ConditionalAttribute:
using System;
using System.Diagnostics;
public class C {
public Object _obj = new object();
public void M()
{
Alpha("This goes away in Release");
Alpha(_obj.GetHashCode() + "...this is ommited");
}
[Conditional("DEBUG")]
public static void Alpha(String s)
{
Console.WriteLine(s);
}
}
See SharpLab for results.
A neat trick you could use for void methods is the ConditionalAttribute, used like this:
[Conditional("DEBUG")]
public static void Alpha(String s)
{
/***/
}
The compiler would remove all calls to those methods if the symbol is not defined.
Also there's this monstrosity:
if (System.Diagnostics.Debugger.IsAttached) /* your debug */
Works in one line, but requires an attached debugger and also is not "removing" the code.
I have a console application. In release environment, it works perfectly at this time. When in IDE debug environment, I don't want the console window close, so I added this function, and calling it in the very end of my program.
[Conditional("DEBUG")]
public static void DebugWaitAKey(string message = "Press any key")
{
Console.WriteLine(message);
Console.ReadKey();
}
It works well for me, when I debug my program. But with unit testing, it still wait for a key before exiting!
The work-around is only unit-testing release edition of my program, or test other functions. But I do want something can identify current session is under unit testing, and use that flag in this function.
I believe this should answer your question. I took a class from there and adapted it to your situation.
/// <summary>
/// Detects if we are running inside a unit test.
/// </summary>
public static class UnitTestDetector
{
static UnitTestDetector()
{
string testAssemblyName = "Microsoft.VisualStudio.QualityTools.UnitTestFramework";
UnitTestDetector.IsInUnitTest = AppDomain.CurrentDomain.GetAssemblies()
.Any(a => a.FullName.StartsWith(testAssemblyName));
}
public static bool IsInUnitTest { get; private set; }
}
Then I added a line to your method which if it is running a test it will not hit the Console.ReadKey();
[Conditional("DEBUG")]
public static void DebugWaitAKey(string message = "Press any key")
{
Console.WriteLine(message);
if(!UnitTestDetector.IsInUnitTest)
Console.ReadKey();
}
Note: This would be considered a hack and would not be considered a best practice.
EDIT:
I also created a sample project on github to demonstrate this code. https://github.com/jeffweiler8770/UnitTest
The simple way if your test runs from a dedicated UnitTest project : use a flag in AppSettings...
I would not investigate around patterns for such a purpose, i would run the test in a dedicated UnitTest project with its own configuration.
If you need to collect data maybe should you simply use traces (they can be customized from your .config file)... ?
Hope this helps...
Rather than looking for whether the program was compiled in debug mode, you can look at whether a debugger is attached:
if (Debugger.IsAttached)
{
Console.WriteLine(message);
Console.ReadKey();
}
Note this will only detect if you start with F5 from Visual Studio, not Ctrl-F5 (i.e. Start with Debugging only)
I used a variation of Jeff's UnitTestDetector. I did not want to check the unit test assembly and wanted to control which unit tests would consider this or not.
So I created a simple class with IsInUnitTest defaulting to false.
Then in the unit test classes where I wanted the conditional code to run I added TestInitializer and TestCleanup where I set the bool accordingly.
Then in my regular code I can use UnitTestDetector.IsInUnitTest
Simple UnitTestDetector class:
/// <summary>
/// Detects if we are running inside a unit test.
/// </summary>
public static class UnitTestDetector
{
static private bool _isInUnitTest = false;
public static bool IsInUnitTest
{
get { return _isInUnitTest; }
set { _isInUnitTest = value; }
}
}
Unit Test to Test this stuff:
[TestClass]
public class UnitTestDetectorTest_WithoutIsInUnitTest
{
[TestMethod]
public void IsInUnitTest_WithoutUnitTestAttribute_False()
{
bool expected = false;
bool actual = UnitTestDetector.IsInUnitTest;
Assert.AreEqual(expected, actual);
}
}
[TestClass]
public class UnitTestDetectorTest_WithIsInUnitTest
{
[TestInitialize()]
public void Initialize()
{
UnitTestDetector.IsInUnitTest = true;
}
[TestCleanup()]
public void Cleanup()
{
UnitTestDetector.IsInUnitTest = false;
}
[TestMethod]
public void IsInUnitTest_WithUnitTestAttribute_True()
{
bool expected = true;
bool actual = UnitTestDetector.IsInUnitTest;
Assert.AreEqual(expected, actual);
}
}
Condition in Code:
if (UnitTestDetector.IsInUnitTest)
return "Hey I'm in the unit test :)";
I know this is old but I really don't like many of these answers, especially anything that hard codes an assembly name or version.
This works well, as long as the class you are testing is not Sealed. It's pretty simple:
Add this class variable to the class you are testing:
protected Boolean IsInUnitTestMode = false;
We default it to false so in production it will always be false.
Add something like this wrapper to your test class
class ProfileTest : Profiles
{
public ProfileTest() : base()
{
IsInUnitTestMode = true;
}
}
In this example Profiles is the class we are testing, ProfileTest is a wrapper class in the test project's namespace. It will never be deployed. The test class uses this to create an instance of the class to be tested:
ProfileTest profiles = new ProfileTest();
As opposed to this:
private Profiles profiles = new Profiles();
The we can use it something like this:
private string ProfilePath
{
get
{
if (IsInUnitTestMode)
return SafeStorage.EnsureFolderExists(Path.Combine(SafeStorage.UserPath, UNITTESTFOLDERNAME)).FullName;
else
return SafeStorage.EnsureFolderExists(Path.Combine(SafeStorage.UserPath, PROFILEFOLDERNAME)).FullName;
}
}
As I said, this won't work with sealed classes, nor will it work well with static ones. With that said the number of times I actually choose to test for the unit test condition is quite rare. This works extremely well for me.
Debug.Assert shows a confusing message box, but I want it to just break if condition is false.
The following works, but is tedious to write:
#if DEBUG
if (!condition) Debugger.Break()
#endif
So I wrote the following function:
public class Util
{
[Conditional("DEBUG")]
public static void Assert(bool condition)
{
if (!condition) Debugger.Break();
}
}
It works, but it breaks in the function and not at its call site. How do I make my Assert function behave like the Break function it wraps?
Matze's comment is correct. Decorating your Assert method with the DebuggerStepThrough attribute sets the break point on the call of the Assert method.
Test program:
[DebuggerStepThrough]
public static void Assert(bool condition)
{
if (!condition) Debugger.Break();
}
static void Main(string[] args)
{
Assert(false); // <-- break point here
Console.ReadKey();
}
Note that you have to turn Just my code on. Go to Options -> Debugging -> Enable Just My Code.
The DebuggerStepThrough attribute as mentioned in Patrick Hofman's answer did not work in my case. I am using Visual Studio 2022, maybe they changed how the debugger handles those attributes.
I had to use the DebuggerHidden attribute. It works with and without enabling Just my code.
I have a unit test (nUnit). Many layers down the call stack a method will fail if it is running via a unit test.
Ideally you would use something like mocking to setup the object that this method is depending on but this is 3rd party code and I can't do that without a lot of work.
I don't want setup nUnit specific methods - there are too many levels here and its a poor way of doing unit test.
Instead what I would like to do is to add something like this deep down in the call stack
#IF DEBUG // Unit tests only included in debug build
if (IsRunningInUnitTest)
{
// Do some setup to avoid error
}
#endif
So any ideas about how to write IsRunningInUnitTest?
P.S. I am fully aware that this is not great design, but I think its better than the alternatives.
I've done this before - I had to hold my nose while I did it, but I did it. Pragmatism beats dogmatism every time. Of course, if there is a nice way you can refactor to avoid it, that would be great.
Basically I had a "UnitTestDetector" class which checked whether the NUnit framework assembly was loaded in the current AppDomain. It only needed to do this once, then cache the result. Ugly, but simple and effective.
Taking Jon's idea this is what I came up with -
using System;
using System.Reflection;
/// <summary>
/// Detect if we are running as part of a nUnit unit test.
/// This is DIRTY and should only be used if absolutely necessary
/// as its usually a sign of bad design.
/// </summary>
static class UnitTestDetector
{
private static bool _runningFromNUnit = false;
static UnitTestDetector()
{
foreach (Assembly assem in AppDomain.CurrentDomain.GetAssemblies())
{
// Can't do something like this as it will load the nUnit assembly
// if (assem == typeof(NUnit.Framework.Assert))
if (assem.FullName.ToLowerInvariant().StartsWith("nunit.framework"))
{
_runningFromNUnit = true;
break;
}
}
}
public static bool IsRunningFromNUnit
{
get { return _runningFromNUnit; }
}
}
Pipe down at the back we're all big enough boys to recognise when we're doing something we probably shouldn't ;)
Adapted from Ryan's answer. This one is for the MS unit test framework.
The reason I need this is because I show a MessageBox on errors. But my unit tests also test the error handling code, and I don't want a MessageBox to pop up when running unit tests.
/// <summary>
/// Detects if we are running inside a unit test.
/// </summary>
public static class UnitTestDetector
{
static UnitTestDetector()
{
string testAssemblyName = "Microsoft.VisualStudio.QualityTools.UnitTestFramework";
UnitTestDetector.IsInUnitTest = AppDomain.CurrentDomain.GetAssemblies()
.Any(a => a.FullName.StartsWith(testAssemblyName));
}
public static bool IsInUnitTest { get; private set; }
}
And here's a unit test for it:
[TestMethod]
public void IsInUnitTest()
{
Assert.IsTrue(UnitTestDetector.IsInUnitTest,
"Should detect that we are running inside a unit test."); // lol
}
Simplifying Ryan's solution, you can just add the following static property to any class:
public static readonly bool IsRunningFromNUnit =
AppDomain.CurrentDomain.GetAssemblies().Any(
a => a.FullName.ToLowerInvariant().StartsWith("nunit.framework"));
I use a similar approach as tallseth
This is the basic code which could be easily modified to include caching.
Another good idea would be to add a setter to IsRunningInUnitTest and call UnitTestDetector.IsRunningInUnitTest = false to your projects main entry point to avoid the code execution.
public static class UnitTestDetector
{
public static readonly HashSet<string> UnitTestAttributes = new HashSet<string>
{
"Microsoft.VisualStudio.TestTools.UnitTesting.TestClassAttribute",
"NUnit.Framework.TestFixtureAttribute",
};
public static bool IsRunningInUnitTest
{
get
{
foreach (var f in new StackTrace().GetFrames())
if (f.GetMethod().DeclaringType.GetCustomAttributes(false).Any(x => UnitTestAttributes.Contains(x.GetType().FullName)))
return true;
return false;
}
}
}
Maybe useful, checking current ProcessName:
public static bool UnitTestMode
{
get
{
string processName = System.Diagnostics.Process.GetCurrentProcess().ProcessName;
return processName == "VSTestHost"
|| processName.StartsWith("vstest.executionengine") //it can be vstest.executionengine.x86 or vstest.executionengine.x86.clr20
|| processName.StartsWith("QTAgent"); //QTAgent32 or QTAgent32_35
}
}
And this function should be also check by unittest:
[TestClass]
public class TestUnittestRunning
{
[TestMethod]
public void UnitTestRunningTest()
{
Assert.IsTrue(MyTools.UnitTestMode);
}
}
References:
Matthew Watson in http://social.msdn.microsoft.com/Forums/en-US/csharplanguage/thread/11e68468-c95e-4c43-b02b-7045a52b407e/
Somewhere in the project being tested:
public static class Startup
{
public static bool IsRunningInUnitTest { get; set; }
}
Somewhere in your unit test project:
[TestClass]
public static class AssemblyInitializer
{
[AssemblyInitialize]
public static void Initialize(TestContext context)
{
Startup.IsRunningInUnitTest = true;
}
}
Elegant, no. But straightforward and fast. AssemblyInitializer is for MS Test. I would expect other test frameworks to have equivalents.
In test mode, Assembly.GetEntryAssembly() seems to be null.
#IF DEBUG // Unit tests only included in debug build
if (Assembly.GetEntryAssembly() == null)
{
// Do some setup to avoid error
}
#endif
Note that if Assembly.GetEntryAssembly() is null, Assembly.GetExecutingAssembly() isn't.
The documentation says: The GetEntryAssembly method can return null when a managed assembly has been loaded from an unmanaged application.
Just use this:
AppDomain.CurrentDomain.IsDefaultAppDomain()
In test mode, it will return false.
I use this only for skipping logic that disables all TraceAppenders in log4net during startup when no debugger is attached. This allows unit tests to log to the Resharper results window even when running in non-debug mode.
The method that uses this function is either called on startup of the application or when beginning a test fixture.
It is similar to Ryan's post but uses LINQ, drops the System.Reflection requirement, does not cache the result, and is private to prevent (accidental) misuse.
private static bool IsNUnitRunning()
{
return AppDomain.CurrentDomain.GetAssemblies().Any(assembly => assembly.FullName.ToLowerInvariant().StartsWith("nunit.framework"));
}
Having a reference to nunit framework doesn't mean that test is actually running. For example in Unity when you activate play mode tests the nunit references are added to the project. And when you run a game the references are exist, so UnitTestDetector would not work correctly.
Instead of checking for nunit assembly we can ask nunit api to check is code under executing test now or not.
using NUnit.Framework;
// ...
if (TestContext.CurrentContext != null)
{
// nunit test detected
// Do some setup to avoid error
}
Edit:
Beware that the TestContext may be automatically generated if it's required.
I have a solution that's closer to what the original poster wanted. The issue is how to set the test flag to indicate the code is executing as part of a test. This can be implemented with 2 lines of code.
I have added an internal variable called RunningNunitTest at the top of the class. Be sure to make this an internal variable and not public. We don't want to export this variable when we build the project. Also this is how we're going to allow NUnit to set it to true.
NUnit does not have access to private variables or methods in our code. This is an easy fix. In between the using statements and the namespace add a [assembly: InternalsVisibleTo("NUnitTest")] decoration. This allows NUint access to any internal variable or method. My NUnit test project is named "NUintTest." Replace this name with the name of your NUint test Project.
That's it! Set RunningNunitTest to true in your NUnit tests.
using NetworkDeviceScanner;
[assembly: InternalsVisibleTo("NUnitTest")] // Add this decoration to your class
namespace NetworkDeviceScannerLibrary
{
public class DetectDevice
{
internal bool RunningNunitTest = false; // Add this variable to your class
public ulong TotalAddressesFound;
public ulong ScanCount;
NUnit Code
var startIp = IPAddress.Parse("191.168.1.1");
var endIp = IPAddress.Parse("192.168.1.128");
var detectDevice = new DetectDevice
{
RunningNunitTest = true
};
Assert.Throws<ArgumentOutOfRangeException>(() => detectDevice.DetectIpRange(startIp, endIp, null));
works like a charm
if (AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(x => x.FullName.ToLowerInvariant().StartsWith("nunit.framework")) != null)
{
fileName = #"C:\Users\blabla\xxx.txt";
}
else
{
var sfd = new SaveFileDialog
{ ... };
var dialogResult = sfd.ShowDialog();
if (dialogResult != DialogResult.OK)
return;
fileName = sfd.FileName;
}
.
Unit tests will skip application entry point. At least for wpf, winforms and console application main() is not being called.
If main method is called than we are in run-time, otherwise we are in unit test mode:
public static bool IsUnitTest { get; private set; } = true;
[STAThread]
public static void main()
{
IsUnitTest = false;
...
}
I was unhappy to have this problem recently. I solved it in a slightly different way. First, I was unwilling to make the assumption that nunit framework would never be loaded outside a test environment; I was particularly worried about developers running the app on their machines. So I walked the call stack instead. Second, I was able to make the assumption that test code would never be run against release binaries, so I made sure this code did not exist in a release system.
internal abstract class TestModeDetector
{
internal abstract bool RunningInUnitTest();
internal static TestModeDetector GetInstance()
{
#if DEBUG
return new DebugImplementation();
#else
return new ReleaseImplementation();
#endif
}
private class ReleaseImplementation : TestModeDetector
{
internal override bool RunningInUnitTest()
{
return false;
}
}
private class DebugImplementation : TestModeDetector
{
private Mode mode_;
internal override bool RunningInUnitTest()
{
if (mode_ == Mode.Unknown)
{
mode_ = DetectMode();
}
return mode_ == Mode.Test;
}
private Mode DetectMode()
{
return HasUnitTestInStack(new StackTrace()) ? Mode.Test : Mode.Regular;
}
private static bool HasUnitTestInStack(StackTrace callStack)
{
return GetStackFrames(callStack).SelectMany(stackFrame => stackFrame.GetMethod().GetCustomAttributes(false)).Any(NunitAttribute);
}
private static IEnumerable<StackFrame> GetStackFrames(StackTrace callStack)
{
return callStack.GetFrames() ?? new StackFrame[0];
}
private static bool NunitAttribute(object attr)
{
var type = attr.GetType();
if (type.FullName != null)
{
return type.FullName.StartsWith("nunit.framework", StringComparison.OrdinalIgnoreCase);
}
return false;
}
private enum Mode
{
Unknown,
Test,
Regular
}
Application.Current is null when running under the unit tester. At least for my WPF app using MS Unit tester. That's an easy test to make if needed. Also, something to keep in mind when using Application.Current in your code.
if (string.IsNullOrEmpty(System.Web.Hosting.HostingEnvironment.MapPath("~")))
{
// Running not as a web app (unit tests)
}
// Running as a web app
There is a really simple solution as well when you are testing a class...
Simply give the class you are testing a property like this:
// For testing purposes to avoid running certain code in unit tests.
public bool thisIsUnitTest { get; set; }
Now your unit test can set the "thisIsUnitTest" boolean to true, so in the code you want to skip, add:
if (thisIsUnitTest)
{
return;
}
Its easier and faster than inspecting the assemblies. Reminds me of Ruby On Rails where you'd look to see if you are in the TEST environment.
Considering your code is normaly run in the main (gui) thread of an windows forms application and you want it to behave different while running in a test you can check for
if (SynchronizationContext.Current == null)
{
// code running in a background thread or from within a unit test
DoSomething();
}
else
{
// code running in the main thread or any other thread where
// a SynchronizationContext has been set with
// SynchronizationContext.SetSynchronizationContext(synchronizationContext);
DoSomethingAsync();
}
I am using this for code that I want to fire and forgot in a gui application but in the unit tests I might need the computed result for an assertation and I don't want to mess with multiple threads running.
Works for MSTest. The advantage it that my code does not need to check for the testing framework itself and if I really need the async behaviour in a certain test I can set my own SynchronizationContext.
Be aware that this is not a reliable method to Determine if code is running as part of a unit test as requested by OP since code could be running inside a thread but for certain scenarios this could be a good solution (also: If I am already running from a background thread, it might not be necessary to start a new one).
I've used the following in VB in my code to check if we ae in a unit test. spifically i didn't want the test to open Word
If Not Application.ProductName.ToLower().Contains("test") then
' Do something
End If
How about using reflection and something like this:
var underTest = Assembly.GetCallingAssembly() != typeof(MainForm).Assembly;
The calling assembly will be where your test cases are and just substitute for MainForm some type that's in your code being tested.