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I am fairly new to C#..
I am using Visual Studio 12, the source I am using was last edited in VS 12.. But my problem is that it's throwing me this error:
First of all, my computer username isn't Martin, it is Administratoring - The creator of this project is Martin.. So that's where I guess it's coming from, but I don't know how to fix this.
I have tried editing in Project > Properties > Build > Output Path - And it still doesn't work. I am not too familiar with C#, and I've spent some time searching up for a solution but can't find it anywhere.. Probably because I don't know what I should be searching up (I've tried searching keywords and quotes from the error, but still nothing)
Try these:
Make sure that output path of project is correct (Project > Properties > Build > Output path)
Go in menu to Build > Configuration Manager, and check if your main/entry project has checked Build. If not, check it.
For those with this kind of problem - another solution:
Pay attention also to Warnings when you build solution. For example, I had referenced a dll built with higher version of .NET (4.5.2) than my main project (4.5)
After I referenced a dll built with 4.0 build process was successful.
Please try with the steps below:
Right click on the Visual Studio Project - Properties - Debug - (Start Action section) - select "Start project" radio button.
Right click on the Visual Studio Project - Properties - Debug - (Enable Debuggers section) - mark "Enable the Visual Studio hosting process"
Save changes Ctrl + Shift + S) and run the project again.
P.S. I experienced the same problem when I was playing with the options to redirect the console input / output to text file and have selected the option Properties - Debug - (Start Action section) - Start external program. When I moved the Solution to another location on my computer the problem occurred because it was searching for an absolute path to the executable file. Restoring the Visual Studio Project default settings (see above) fixed the problem. For your reference I am using Visual Studio 2013 Professional.
I had the same problem and unfortunately non of above answers worked for me . the solution that worked for me is :
right click on your startup project and select Properties - Debug and change "start external program: " to the correct path
Done!
Switch Target framework to 4.5.2 or something higher and bring it back to your original version (example: 4.5) then when you build, it will work.
You are not set the startup project so only this error occur. Mostly this problem occur when your working with more project in the single solution.
First right click on your project and "Set as Start Up Project" and/or right click on the start up file inside the selected project and click "Set StartUp File".
I also get this error quite often.
I solve this by modifying the code (doing a very small change), saving it, then building the solution again.
In my case I had added a project to a solution manually, where that project was targeting a higher .NET version than the rest of the projects that were referencing it. Strange... there would normally be a somewhat more verbose, literal and descriptive error in such cases.
There wasn't a real error but there was a warning that said as much.
Go to Project > properties > Debug Tab and set the Launch to "Project"
I had the same problems. I had to change file rights. Unmark "read only" in their properties.
So... it’s mid 2021 and I’m using visual Studio 2019 (version 16.10.2) which is the current version available, on a windows 10 pc.
I had to start a new project and following this steps solved the issue;
When at the menu that says “Create new project”
After you’ve selected your project template it takes you to another menu that says “Configure your new project”
On this menu there’s an option that says “Place solution and project in the same directory”.
By default this option was not checked, so I checked it and it solved the issue.
I had the same problem with visual studio 2015 , and I found that there is reference is marked so I just deleted it , maybe you can delete this reference or reinstall it again
What solved it for me was deleting the line
<ImplicitUsings>enable</ImplicitUsings>
from the project property file. It caused Visual Studio to generate a (useless) file with multiple global using directive.
I faced the same problem , but in my solution i had many projects so in the solution configuration the start up project was by mistake a class library i changed the startup project and then i worked like a charm
right click on the sln => common proprties => choose right startup project .
Please can someone could explain why I get this error and what to do to fix it (or what I'm doing wrong!). The steps I have taken are
Download Source code from http://www.codeproject.com/Articles/16859/AForge-NET-open-source-framework
Opening in VS2010 shows the references cannot be found
Re-Add all 3 references from PlayingCardRecognition\bin\Release so no further warnings
When I try and build or Run I get the following message
To fix this issue, do these steps:
Right click the Project name in Solution Explorer of Visual Studio
Select Set as StartUp Project from the menu
Re-run your project
It should work!
If it did not work, be sure that you have set your start page. If your project is C# Windows Application or C# Console Application, try this:
Right click the Project name in Solution Explorer of Visual Studio
Select Properties
Select the Application tab
In the Output Type drop box
Select the correct application type of your project
Re-run your project and let me know if it won’t work.
The project type set as the Start-up project in that solution is of type ClassLibrary. DUe to that, the output is a dll not an executable and so, you cannot start it.
If this is an error then you can do this:
A quick and dirty fix for this, if that is the only csproj in the solution is to open the .csproj file in a text editor and change the value of the node <ProjectGuid> to the Guid corresponding to a WinForms C# project. (That you may obtain from a google search or by creating a new project and opening the .csproj file generated by Visual Studio to find out what the GUID for that type is). (Enjoy - not many people know about this sneaky trick)
BUT: the project might be a class library rightfully and then you should reference it in another project and use it that way.
.Exe's and .dll's are both assemblies. The key difference is that executeables define an entry point Main which can be invoked by the runtime. The error
"Class library cannot be started directly"
is due to the fact that said .dll's do not have a Main. To fix this issue, change the project type to a Windows application/Console application and define an entry point. Or, add a new project that is of type Windows application/Console application and reference said .dll.
The project is a class library. It cannot be run or debugged without an executable project (F5 doesn't work!!!). You can only build the project (Ctrl+Shift+B).
If you want to debug the code add a console application project (set it as the start up project) to the solution and add the reference to the library.
The project you downloaded is a class library. Which can't be started.
Add a new project which can be started (console app, win forms, what ever you want) and add a reference to the class library project to be able to "play with it".
And set this new project as "Startup project"
The project you've downloaded is a class library, not an executable assembly. This means you need to import that library into your own project instead of trying to run it directly.
Your project type is a class library one would suspect, add a ConsoleApplication or WindowsApplication and use that as your startup object. Reference this project and then access the code.
If you convert the WPF application to Class library for get the projects .dll file.After that convert the same project to the WPF application you get the following error.
Error:".exe does not contain a static main method suitable for an entry point".
Steps to troubleshoot:
1.Include the App.xaml file in the respective project.
2.Right Click on App.xaml file change the build action to Application Definition
3.Now Build your project
Goto the Solution properties -> on Build right side you see the startup project type. here you need to select the console appication/windows appication.
If you got this issue (got it in Visual Studio 2017 RC), and you don't get any of the things listed by Mak post from step 3 onward "4 In the Output Type drop box....", it is because you made a Class Library app when you want to create a cross platform app, so here is the solution :
1 Start a new project
2 select Visual C# and cross-platform app.
3 select cross-platform app (Xamarin and native app)
4 select blank form.
From then , right click, select as startup project and build as mentioned by Mak, and it should work.
If you can afford to start from scratch, it could do the trick as it did for me.
This could do the trick for the main issue as well, but must be adapted to your current version of Visual Studio ("Xamarin.forms portable" for visual studio 2015 for example).
Bye!
VS -> Debug -> Attach unity debugger -> double click project
Set your api project to a startup project:
Right click the api Project than choose Set as startup Project.
Just right click on the Project Solution A window pops up. Expand the common Properties. Select Start Up Project
In there on right hand side Select radio button with Single Startup Project Select your Project in there and apply.
That's it. Now save and build your project. Run the project to see the output.
_Sarath#F1
To fix this issue, do these steps:
Right click the Project name in Solution Explorer of Visual Studio
Select Set as StartUp Project from the menu
Re-run your project It should work!
The RC class is not linked to a database, it is a simple class. The class is at only one place and is not partial. The Aérochem.Domain dll project compiles just fine.
Note: If I select one of the two identical namespaces in the quick fix menu, it does nothing.
Note2: This happens to a couple of classes (some related to a database, some not)
Is there a fix to that or a way to figure what's wrong?
I had the same problem. I use ReSharper. The solution to my problem was not cleaning the solution but deleting the suo-file.
Hope that helps.
As for the reference of any future users: This thread covers four answers whereas two are in the comments. I have faced the issue several times, three of these answers have helped me in the past, so if you face the same issue, try any of these:
Clean and/or Rebuild the Solution then reanalyze the files in Resharper.
Restart Visual Studio then reanalyze
Delete the bin/ folder then reanalyze
(Apparently deleting the suo-file can help, too, although I never had to do that and can't understand how it should help)
A combination of the three above.
(This is not really a new answer, it is more of a comment on the variety of answers and comments found - it is a community wiki so feel free to adapt it if necessary)
For ReSharper users that, like me, don't want to delete their solution's *.suo file:
Clear your caches via: ReSharper -> Options -> Environment -> General -> Clear Caches!
Thanks go to AUSTX_RJL for his comment to this answer. I wanted to give his valuable info more visibility.
The .dll was already in my /bin folder.
When I deleted it, it got rid of this error.
I had this problem and also ReSharper installed on visual studio.
I open bug ticket on ReSharper tracker and the development team advised me to do:
Solution:
This problem can be solved by removing the Solution User Options (.Suo) File. This file is stored in the project root but is hidden. you need to check Folder Options-> View-> Show hidden files, folders, drives. and you need to close visual studio if you have open this project because is used by visual studio.
I had the same problem while two packages were ambiguously referencing the same dll, and this is what worked for me:
I have given an alias name to one of the packages (named Dapper.StrongName), by putting the following into my .csproj file:
<Target Name="ChangeNameAlias" BeforeTargets="FindReferenceAssembliesForReferences;ResolveReferences">
<ItemGroup>
<ReferencePath Condition="'%(FileName)' == 'Dapper.StrongName'">
<Aliases>AliasName</Aliases>
</ReferencePath>
</ItemGroup>
</Target>
And then added the namespace as using AliasName::Dapper;
I added a post here: Ambiguous extension methods
See related articles:
extern alias (C# Reference)
:: operator (C# Reference)
C# 2.0: Using different versions of
the same dll in one application
For me it was because I had referenced the DLL both by Project reference and Assembly reference. Deleting the Assembly reference fixed the issue.
If your project structure contains more than one project under one solution, then you have to delete the content of the bin folder in every project. Doing so solved the error that i was facing.
In my case, i have referenced the proyect X inside itself. So the problem wasn't ReSharper (but it was ReSharper who added the reference...)
I had this problem in a .NET standard project (I call it the host project). The namespace causing the problem was in another referenced project (which was also a .NET standard project) in the same solution.
I did everything: clean, delete resharper cache, close soln, delete .suo, delete binaries. Nothing seemed to work.
Then I converted the host project to .NET framework and then the problem disappeared.
I know this is a pretty old issue, but maybe this will help someone. If using c# razor in Asp.Net Core 2+, if you have this problem.
1) Copy the content of the file to notepad.
2) Delete the .cshtml file.
3) Create the .cshtml file with the same name.
4) Copy the content from notepad into the new file
I don't know if this is just a weird bug, or a consequence of upgrading a project from Core 1.0 to 2+, but it FINALLY fixed the problem for me. This was an issue for me in both Visual Studio 2017 and 2019.
I had this issue in Rider, and going to File | Invalidate Caches | Invalidate and Restart fixed it for me
I've download sample code with C#. but when I run I get this error message:
A project with an Output type of Class Library cannot be started
directly In order to debug this project, add an executable project to
this solution which references the library project. Set the executable
project as the startup project.
Please give me a solution.
The currently selected startup project is a Class Library.
You need an entry point for your application. Does your solution contain multiple projects?
Are you sure you want to 'run' the Class Library?
Possibly you've downloaded a Class Library solution only. In that case there might be unit tests that you can 'debug' to step-trough the code.
Update
In response to your comment, these are possibilities to run the class library:
Create a console application and reference the class library. Then 'use' its contents
Debug an unit-test project
start existing client project
If you have a project with an executable right-click this and select "Set as start project" - if not you have to write one to debug your code (or use Unit-Tests).
The debug settings of your Visual Studio development environment might be left blank. Please check if the following highlighted fields are missing, if they are missing then fill it up with your specific executable.
These fields are required to let the VS start the program for debugging. In the above picture, I'm developing a VSPackage so the:
The external program is devenv.exe
Command line argument is /rootsuffix Exp (for starting the experimental instance).
Note: I can assure you the answers mentioned in here didn't help me fix the issue because my project was already set as a startup project, now I came across an MSDN blog which helped me and lead to this answer.
You need to check that you have the startup project setup correctly.
If there is more than one project in the solution, right click on the one that should be run when you compile and choose Set as startup project
I was trying to run a Debug test with breakpoint in the specFlow feature.cs file instead of the Step.cs file. Put the breakpoint in the Step.cs file and it's working as expected. Thanks!
Try to close Visual Studio and restart it by opening the file you are trying to debug from Unity
None of the answers provided above helped me resolve this error, this is what resolved the issue for me.
Right click on the solution and select "Properties", which is in my case "Sintctech.Data".
Select the section called "Application".
Check what you have selected as your output type. If it is "Windows Application", change it to "Console Appication".
Rebuild the solution
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'">
<StartAction>Program</StartAction>
<StartProgram>C:\Program Files (x86)\Microsoft Office\Office14\excel.exe</StartProgram>
<StartArguments></StartArguments>
<StartWorkingDirectory></StartWorkingDirectory>
<EnableUnmanagedDebugging>true</EnableUnmanagedDebugging>
</PropertyGroup>
</Project>
Why does Rebuild fail with no errors?
Since this morning, this error keeps showing up. I build the entire solution (25 C# managed projects) and a "Rebuild All failed" appears, but without any errors! (I have 13 warnings about COM not supporting Generics, but it's "normal" because one dll is exposed as COM.)
Not an answer per se - but you're better off looking at the output window and seeing what it says there.
Also, to help with that you might want to look at your MSBuild verbosity - as shown on this screenshot (last two options):
Beware - the highest level generates a MASSIVE amount of information.
Finally - running msbuild from the solution folder in a command prompt will really nail the issue - because error messages and warnings come up in red and yellow respectively.
I found my own solution and it is simple:
When this error occurs, save the project and close VS 2013. After that, re-open VS2013 and open the last project.
It works like a charm. But it is very annoying every time!
Many people reported this problem in VS2010, VS2012 and VS2013.
Could be a corrupt Solution User Options file.
Close the solution, delete its .suo (.v12.suo for VS2012+), reopen the solution, and Visual Studio will build a new one. You will lose the StartUp Project, breakpoints, bookmarks, which files are open, which projects/folders are expanded, etc. But that's all minor compared to the solution not building!
I had the same problem. I was trying to refrence a higher .net framework version(4.5.2) to lower .net framework version(4.5) which was causing build error. I made the version same in both projects and it worked.
Check the Output Window (View -> Output) as that will tell you what's going wrong. Sometimes a reference might be missing or there is an issue with the targeted version of .NET for one project in a solution.
Have you tried to clean the solution befor rebiuld it?
This is the list of checks & things I would do if I were you (try to build after each step):
Is error list activated? (Sometimes I forgot to activate and I can see only warnings & messages)
Check output window for error messages..
Clean solution.
Double check after clean that everything is deleted from debug folders.
Build it in release mode.
Build solution project to project until you isolate problematic project.
Remove COM and comment code to see if is this the source of problem.
Restart VS2010.
Restart windows.
Few moments ago I fix it with repair of .NET Framework installation (.NET Framework v4.0 Extended in my case).
I had the same issue in VS 2015. I tried the following with no success:
Close VS project and reopen
Close all open VS projects and reopen just the project that had the issue
Clean solution
Rebuild solution
Delete all files in bin\debug and bin\release
Lastly I tried Keith Robertson's answer, delete .suo (\Visual Studio 2015\Projects\[ProjectName]\.vs\[ProjectName]\v14\.suo). Although this didn't get me a good build, it did finally give me an error message stating that I had two entry points to my application. I went to application properties (Alt + Enter) and select a Startup object from the drop down.
This error seems a bit generic to me. I also went through this situation, but I managed to solve it differently than any of the ones mentioned here.
I have a project and several dependencies. And one of these dependencies has undergone a change.
When compiling the main project in debug mode, I verified that everything was ok.
However, switching to release mode and recompiling the problem occurred.Rebuild all failed and 0 Errors
By analyzing the debug output, I encountered an error:
Although the build dependencies are configured correctly. When compiling in release mode, the main project did not find the new method created in the secondary project.
So I had to recompile each secondary project one by one in release mode. After that, I recompiled the main project and everything worked.
Hope it helps someone!
I just had the same thing. For me, it helped to restart VS and run it as Administrator.
Select the appropriate target framework
- Right click on project
- Properties
- In application tab, Select the target framework
clean the solution
Try and build each project and see where the issue is.
Check each of the references (of each project) to make sure not have the yellow warning sign
Has the solution ever built?
I just had this happen to me, and realized that I left a '#error' line in my code and forgot about it. When I tried to build, the build failed but the #error line didn't show up in my errors.
Try searching all for '#error'
I fixed it on my new implementation of Visual Studio 2013 by going to the database project / Project Settings and noticing that the Target Platform was SQL Server 2014 instead of 2012 like it should be.
Once chance of getting this error is when we try re naming the service reference name, we give some other name in the service reference, but in the namespace some where it will be referring the old name, so if you delete and add a service reference then keep the same name, else we may face this error, but we can see the error in the Output window.
There are apparently many causes of this. I just found the cause of my issue: the .NET version of a new project I created was higher than the version of the top-level project. (4.5.2 vs 4.0)
I got a similar issue today, and fixed it with repair.
Start
Run…
Appwiz.cpl
(Find your installed Visual Studio version)
Right click
Change
Repair
In my case it was the wrong date and time of computer.
I was getting no feedback/messages/errors. Just that all projects failed to build.
I closed and tried again--I noticed an error saying "you are not authorized to access..."
I clicked on my account, re-entered my credentials, and rebuilt the solution.
Voila! I got what I am used to seeing when I build a solution -- plenty of errors in all their glory.
Hope this helps someone.
Here's yet another reason which may sound familiar to some. I had integrated some code into my solution that wrapped a DLL. The C# code file that came with it offered a nice managed API and handled the low-level LoadLibrary stuff to access the DLL. Both had the same base name, so I had SomeName.cs and SomeName.dll. I could just drop it into any project and it would work.
This wasn't so nice after a while as I started using it in different projects. I got copies of both the DLL and the wrapper code in multiple projects. So I figured it would be better to drop the wrapper code and the DLL into a new class library project and then reference that new project from other projects.
After I had done that, I started to get this issue. The build went well up until the very last stage and then failed without error. Output showed nothing but successes.
The problem was the name of the wrapping class library project. I used the same base name (SomeName) for this. By default the assembly name would be SomeName.dll and I already had one such file (the DLL to be wrapped), thus I had a conflict with output files.
After renaming the wrapping project and its output assembly to SomeNameWrapper, the problem went away.
This may not be your exact cause but it seems likely you have some name clash or deployment issue as well. And it is not surprising the compiler won't give you an error because there is no problem in the compilation phase, the trouble starts with deployment and apparently this does not come out in an obvious way.
I had the same problem the original poster was displaying with 0 errors and Rebuild all succeeded. The Output tab showed a message that a referenced dll was built with a higher version of the .NET Framework.
Changing the .NET framework to match resolved the issue I was having with 0 Errors and Rebuild All succeeded.
The solution:
Because Prerequisites not set for debug set only for release
01-Change solution configuration ( in main screen )
set (debug to release)
set solution platform to (Any CPU)
02-Set Prerequisites for debug ( If you want to continue in debug mode )
03-set target platform version for all Projects
Some of the files included in your solution are not in the correct directories, or you have changed the name of one or more directories in your application. In the solution explorer under Setup review the list of all files and remove those that are not properly listed in the SourcePath Property.
One of my dependency in View file caused this. Check your view files for any dependencies which is not injected yet.