Long path \? workaround not working on some installs












5














The app I'm working on needs to handle files with very long file/path names. It's a .Net 4.6 application so I've implemented the pre-4.6.2 workaround to allow the \? syntax as outlined here and here.



This is the code I'm using to enable the feature (I can't modify the app.config so this has to be set in code):



var type = Type.GetType("System.AppContext");
if (type != null)
{
AppContext.SetSwitch("Switch.System.IO.UseLegacyPathHandling", false);
AppContext.SetSwitch("Switch.System.IO.BlockLongPaths", false);

var switchType = Type.GetType("System.AppContextSwitches");
if (switchType != null)
{
// We also have to reach into System.AppContextSwitches and manually update the cached private versions of these properties (don't ask me why):

var legacyField = switchType.GetField("_useLegacyPathHandling", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
legacyField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.

var blockingField = switchType.GetField("_blockLongPaths", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
blockingField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.
}
}


This works (yay!) on all the machines we've tested on, except one (boo!). The machine in question is a Windows 10 Pro installation, like the others, and has the same registry settings in the [ComputerHKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlFileSystem] namespace.



The error message on this particular machine is:




The given path format is not supported




The one difference we can see on that machine is that when looking at a very long file in Windows File Explorer, the 'Location' field uses the \? syntax in the r-click > Properties menu.



I'm guessing that there's some registry key that is causing both that difference in File Explorer, and the failure of my fix, but somewhere other than the FileSystem namespace mentioned above.



Has anyone encountered a similar issue, or have an idea of other registry areas that might be relevant?










share|improve this question




















  • 1




    Any error message?
    – Rui Jarimba
    Nov 7 at 16:06










  • @RuiJarimba Good question! It's "The given path format is not supported". I've updated my question.
    – technophebe
    Nov 7 at 16:10






  • 1




    What is the version of .NET installed on that machine? Is it exactly the same as in the other machines?
    – Rui Jarimba
    Nov 7 at 16:18






  • 1




    A shot in the dark - check this post
    – Rui Jarimba
    Nov 7 at 16:28






  • 1




    I'll do some exploration around that, many thanks.
    – technophebe
    Nov 7 at 16:51
















5














The app I'm working on needs to handle files with very long file/path names. It's a .Net 4.6 application so I've implemented the pre-4.6.2 workaround to allow the \? syntax as outlined here and here.



This is the code I'm using to enable the feature (I can't modify the app.config so this has to be set in code):



var type = Type.GetType("System.AppContext");
if (type != null)
{
AppContext.SetSwitch("Switch.System.IO.UseLegacyPathHandling", false);
AppContext.SetSwitch("Switch.System.IO.BlockLongPaths", false);

var switchType = Type.GetType("System.AppContextSwitches");
if (switchType != null)
{
// We also have to reach into System.AppContextSwitches and manually update the cached private versions of these properties (don't ask me why):

var legacyField = switchType.GetField("_useLegacyPathHandling", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
legacyField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.

var blockingField = switchType.GetField("_blockLongPaths", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
blockingField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.
}
}


This works (yay!) on all the machines we've tested on, except one (boo!). The machine in question is a Windows 10 Pro installation, like the others, and has the same registry settings in the [ComputerHKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlFileSystem] namespace.



The error message on this particular machine is:




The given path format is not supported




The one difference we can see on that machine is that when looking at a very long file in Windows File Explorer, the 'Location' field uses the \? syntax in the r-click > Properties menu.



I'm guessing that there's some registry key that is causing both that difference in File Explorer, and the failure of my fix, but somewhere other than the FileSystem namespace mentioned above.



Has anyone encountered a similar issue, or have an idea of other registry areas that might be relevant?










share|improve this question




















  • 1




    Any error message?
    – Rui Jarimba
    Nov 7 at 16:06










  • @RuiJarimba Good question! It's "The given path format is not supported". I've updated my question.
    – technophebe
    Nov 7 at 16:10






  • 1




    What is the version of .NET installed on that machine? Is it exactly the same as in the other machines?
    – Rui Jarimba
    Nov 7 at 16:18






  • 1




    A shot in the dark - check this post
    – Rui Jarimba
    Nov 7 at 16:28






  • 1




    I'll do some exploration around that, many thanks.
    – technophebe
    Nov 7 at 16:51














5












5








5







The app I'm working on needs to handle files with very long file/path names. It's a .Net 4.6 application so I've implemented the pre-4.6.2 workaround to allow the \? syntax as outlined here and here.



This is the code I'm using to enable the feature (I can't modify the app.config so this has to be set in code):



var type = Type.GetType("System.AppContext");
if (type != null)
{
AppContext.SetSwitch("Switch.System.IO.UseLegacyPathHandling", false);
AppContext.SetSwitch("Switch.System.IO.BlockLongPaths", false);

var switchType = Type.GetType("System.AppContextSwitches");
if (switchType != null)
{
// We also have to reach into System.AppContextSwitches and manually update the cached private versions of these properties (don't ask me why):

var legacyField = switchType.GetField("_useLegacyPathHandling", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
legacyField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.

var blockingField = switchType.GetField("_blockLongPaths", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
blockingField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.
}
}


This works (yay!) on all the machines we've tested on, except one (boo!). The machine in question is a Windows 10 Pro installation, like the others, and has the same registry settings in the [ComputerHKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlFileSystem] namespace.



The error message on this particular machine is:




The given path format is not supported




The one difference we can see on that machine is that when looking at a very long file in Windows File Explorer, the 'Location' field uses the \? syntax in the r-click > Properties menu.



I'm guessing that there's some registry key that is causing both that difference in File Explorer, and the failure of my fix, but somewhere other than the FileSystem namespace mentioned above.



Has anyone encountered a similar issue, or have an idea of other registry areas that might be relevant?










share|improve this question















The app I'm working on needs to handle files with very long file/path names. It's a .Net 4.6 application so I've implemented the pre-4.6.2 workaround to allow the \? syntax as outlined here and here.



This is the code I'm using to enable the feature (I can't modify the app.config so this has to be set in code):



var type = Type.GetType("System.AppContext");
if (type != null)
{
AppContext.SetSwitch("Switch.System.IO.UseLegacyPathHandling", false);
AppContext.SetSwitch("Switch.System.IO.BlockLongPaths", false);

var switchType = Type.GetType("System.AppContextSwitches");
if (switchType != null)
{
// We also have to reach into System.AppContextSwitches and manually update the cached private versions of these properties (don't ask me why):

var legacyField = switchType.GetField("_useLegacyPathHandling", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
legacyField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.

var blockingField = switchType.GetField("_blockLongPaths", System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);
blockingField?.SetValue(null, (Int32)(-1)); // <- caching uses 0 to indicate no value, -1 for false, 1 for true.
}
}


This works (yay!) on all the machines we've tested on, except one (boo!). The machine in question is a Windows 10 Pro installation, like the others, and has the same registry settings in the [ComputerHKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlFileSystem] namespace.



The error message on this particular machine is:




The given path format is not supported




The one difference we can see on that machine is that when looking at a very long file in Windows File Explorer, the 'Location' field uses the \? syntax in the r-click > Properties menu.



I'm guessing that there's some registry key that is causing both that difference in File Explorer, and the failure of my fix, but somewhere other than the FileSystem namespace mentioned above.



Has anyone encountered a similar issue, or have an idea of other registry areas that might be relevant?







c# windows file registry file-handling






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 7 at 16:12









Rui Jarimba

7,09662958




7,09662958










asked Nov 7 at 16:04









technophebe

346110




346110








  • 1




    Any error message?
    – Rui Jarimba
    Nov 7 at 16:06










  • @RuiJarimba Good question! It's "The given path format is not supported". I've updated my question.
    – technophebe
    Nov 7 at 16:10






  • 1




    What is the version of .NET installed on that machine? Is it exactly the same as in the other machines?
    – Rui Jarimba
    Nov 7 at 16:18






  • 1




    A shot in the dark - check this post
    – Rui Jarimba
    Nov 7 at 16:28






  • 1




    I'll do some exploration around that, many thanks.
    – technophebe
    Nov 7 at 16:51














  • 1




    Any error message?
    – Rui Jarimba
    Nov 7 at 16:06










  • @RuiJarimba Good question! It's "The given path format is not supported". I've updated my question.
    – technophebe
    Nov 7 at 16:10






  • 1




    What is the version of .NET installed on that machine? Is it exactly the same as in the other machines?
    – Rui Jarimba
    Nov 7 at 16:18






  • 1




    A shot in the dark - check this post
    – Rui Jarimba
    Nov 7 at 16:28






  • 1




    I'll do some exploration around that, many thanks.
    – technophebe
    Nov 7 at 16:51








1




1




Any error message?
– Rui Jarimba
Nov 7 at 16:06




Any error message?
– Rui Jarimba
Nov 7 at 16:06












@RuiJarimba Good question! It's "The given path format is not supported". I've updated my question.
– technophebe
Nov 7 at 16:10




@RuiJarimba Good question! It's "The given path format is not supported". I've updated my question.
– technophebe
Nov 7 at 16:10




1




1




What is the version of .NET installed on that machine? Is it exactly the same as in the other machines?
– Rui Jarimba
Nov 7 at 16:18




What is the version of .NET installed on that machine? Is it exactly the same as in the other machines?
– Rui Jarimba
Nov 7 at 16:18




1




1




A shot in the dark - check this post
– Rui Jarimba
Nov 7 at 16:28




A shot in the dark - check this post
– Rui Jarimba
Nov 7 at 16:28




1




1




I'll do some exploration around that, many thanks.
– technophebe
Nov 7 at 16:51




I'll do some exploration around that, many thanks.
– technophebe
Nov 7 at 16:51












1 Answer
1






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oldest

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0














You can set those AppContext switches on a machine-wide basis via the registry if you don't want to set them in each App.config file individually:



enter image description here



These settings will affect all .NET apps that don't specify a different value in their App.config file. That is, the registry setting only changes the default value, which can still be overridden with app-specific values by specifying <AppContextSwitchOverrides value="..." />







EnableLongPath.reg :



Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINESOFTWAREMicrosoft.NETFrameworkAppContext]
"Switch.System.IO.BlockLongPaths"="false"
"Switch.System.IO.UseLegacyPathHandling"="false"





C:>regedit.exe EnableLongPath.reg






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    0














    You can set those AppContext switches on a machine-wide basis via the registry if you don't want to set them in each App.config file individually:



    enter image description here



    These settings will affect all .NET apps that don't specify a different value in their App.config file. That is, the registry setting only changes the default value, which can still be overridden with app-specific values by specifying <AppContextSwitchOverrides value="..." />







    EnableLongPath.reg :



    Windows Registry Editor Version 5.00

    [HKEY_LOCAL_MACHINESOFTWAREMicrosoft.NETFrameworkAppContext]
    "Switch.System.IO.BlockLongPaths"="false"
    "Switch.System.IO.UseLegacyPathHandling"="false"





    C:>regedit.exe EnableLongPath.reg






    share|improve this answer


























      0














      You can set those AppContext switches on a machine-wide basis via the registry if you don't want to set them in each App.config file individually:



      enter image description here



      These settings will affect all .NET apps that don't specify a different value in their App.config file. That is, the registry setting only changes the default value, which can still be overridden with app-specific values by specifying <AppContextSwitchOverrides value="..." />







      EnableLongPath.reg :



      Windows Registry Editor Version 5.00

      [HKEY_LOCAL_MACHINESOFTWAREMicrosoft.NETFrameworkAppContext]
      "Switch.System.IO.BlockLongPaths"="false"
      "Switch.System.IO.UseLegacyPathHandling"="false"





      C:>regedit.exe EnableLongPath.reg






      share|improve this answer
























        0












        0








        0






        You can set those AppContext switches on a machine-wide basis via the registry if you don't want to set them in each App.config file individually:



        enter image description here



        These settings will affect all .NET apps that don't specify a different value in their App.config file. That is, the registry setting only changes the default value, which can still be overridden with app-specific values by specifying <AppContextSwitchOverrides value="..." />







        EnableLongPath.reg :



        Windows Registry Editor Version 5.00

        [HKEY_LOCAL_MACHINESOFTWAREMicrosoft.NETFrameworkAppContext]
        "Switch.System.IO.BlockLongPaths"="false"
        "Switch.System.IO.UseLegacyPathHandling"="false"





        C:>regedit.exe EnableLongPath.reg






        share|improve this answer












        You can set those AppContext switches on a machine-wide basis via the registry if you don't want to set them in each App.config file individually:



        enter image description here



        These settings will affect all .NET apps that don't specify a different value in their App.config file. That is, the registry setting only changes the default value, which can still be overridden with app-specific values by specifying <AppContextSwitchOverrides value="..." />







        EnableLongPath.reg :



        Windows Registry Editor Version 5.00

        [HKEY_LOCAL_MACHINESOFTWAREMicrosoft.NETFrameworkAppContext]
        "Switch.System.IO.BlockLongPaths"="false"
        "Switch.System.IO.UseLegacyPathHandling"="false"





        C:>regedit.exe EnableLongPath.reg







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 23 at 2:56









        Glenn Slayden

        8,58616074




        8,58616074






























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