CSProj - NET5: Unable to create project with path length > 259 characters

Question

CSProj - NET5: Unable to create project with path length > 259 characters

Paul Quinn 1

With a project where the path to the csproj is (including the csproj filename) is greater than 259 char, in VS, if I:

Create a new project (any, inc class lib) from a template I get:
"Consider reducing the length of the name or location for this solution or project. The system will fail to create nested files that exceed the maximum allowed path length."
Create the project elsewhere higher up the filesystem, then move, and try to add the project to an existing solution, VS crashes
Create the project elsewhere higher up the filesystem, then move, and try to open the project, VS doesn't open (fails silently?)
Create using dotnet new writes the files to the filesystem, but then the projects won't load (see above)

I've tried with both VS (Community) 16.9.0p3 and 16.8.4.
I've tried the long path support reg keys/group policy switches (with reboot), am running W10Pro 20H2 (19042.782)

I thought long paths were supported in NET5/VS/Windows now? This shouldn't be happening should it....?

David Lowndes 4,726 Reputation points

2021-01-26T16:42:59.71+00:00

Report it as a bug using the VS "Report a Problem" facility.
Be sure to include a sample project and clear instructions that anyone can use to reproduce the problem - be precise, otherwise it's likely to get dismissed.
Alberto Poblacion 1,571 Reputation points

2021-01-26T21:37:18.583+00:00

Long paths are supported in modern Windows and NET5, which means that at runtime your program will probably be able to handle reading and writing files under long paths. However, Visual Studio itself has existed and been evolving for a long time, so it is perfectly possible that it may contain legacy code which is limited in its capabilities. For example, it may contain internal buffers that are dimensioned to 256 characters. This could explain why Visual Studio might be rejecting long paths. It should probably be considered a bug; you can report it via "report a problem", as has already been suggested.
As a workaround, you could create a symbolic link at a higher level in the file system pointing to the actual folder where you want to keep your files, and open the Visual Studio project from the symbolic link. Yes, it is a kludge, but it would serve as a workaround if you really need to have your files deep.
cheong00 3,486 Reputation points Volunteer Moderator

2021-01-27T02:19:25.88+00:00

Actually .NET runtime only allow you to use path with >259 characters if the path is prefixed with "\?\".

.NET Core runtime will do this automatically for you, but the full version .NET framework that VS runs on won't (.NET 5 support for WinForm is still limited).

I believe the next version of VS will run on .NET 5 or 6, so this issue will go away.

1 answer

Your answer

David Lowndes 4,726 Reputation points

2021-01-26T16:42:59.71+00:00

Report it as a bug using the VS "Report a Problem" facility.
Be sure to include a sample project and clear instructions that anyone can use to reproduce the problem - be precise, otherwise it's likely to get dismissed.
Alberto Poblacion 1,571 Reputation points

2021-01-26T21:37:18.583+00:00

Long paths are supported in modern Windows and NET5, which means that at runtime your program will probably be able to handle reading and writing files under long paths. However, Visual Studio itself has existed and been evolving for a long time, so it is perfectly possible that it may contain legacy code which is limited in its capabilities. For example, it may contain internal buffers that are dimensioned to 256 characters. This could explain why Visual Studio might be rejecting long paths. It should probably be considered a bug; you can report it via "report a problem", as has already been suggested.
As a workaround, you could create a symbolic link at a higher level in the file system pointing to the actual folder where you want to keep your files, and open the Visual Studio project from the symbolic link. Yes, it is a kludge, but it would serve as a workaround if you really need to have your files deep.
cheong00 3,486 Reputation points Volunteer Moderator

2021-01-27T02:19:25.88+00:00

Actually .NET runtime only allow you to use path with >259 characters if the path is prefixed with "\?\".

.NET Core runtime will do this automatically for you, but the full version .NET framework that VS runs on won't (.NET 5 support for WinForm is still limited).

I believe the next version of VS will run on .NET 5 or 6, so this issue will go away.

Answer 1

Dylan Zhu-MSFT 6,426

Hi paulquinn,

Please refer to this document: Maximum Path Length Limitation

Add "\?\" before your long path
Enable long path in system registry

Best Regards,
Dylan

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CSProj - NET5: Unable to create project with path length > 259 characters

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