Uwp C++ Fopen Can Open a File for Read but Not Write
In the one of the recent projects I had a requirement that UWP application should access the file from the external system (C: drive) and the path to this file shold be configurable using surround variables. I saw many questions in the Internet nigh it so in this article I nowadays how to configure permissions and awarding so it can access external file arrangement and environment variables.
Setup application permissions
Probably you know it just just in case - UWP applications work in "sandbox" so they also take their isolated storage to go along files. If you would similar to access external directories (similar C:), you accept to set the right permissions in the awarding manifest and besides in the Windows x organisation.
Setup permissions in the application's manifest
Open up "Packet.appxmanifest" file in the text editor (you tin right click on the file and select "View Code").
At the top of the file in the "Package" section add together below declarations:
xmlns : rescap = "http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities" IgnorableNamespaces = "uap mp rescap" Whole section should look like below:
< Package xmlns = "http://schemas.microsoft.com/appx/manifest/foundation/windows10" xmlns : mp = "http://schemas.microsoft.com/appx/2014/phone/manifest" xmlns : uap = "http://schemas.microsoft.com/appx/manifest/uap/windows10" xmlns : rescap = "http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities" IgnorableNamespaces = "uap mp rescap" > Now in the "Capabilities" section add beneath declarations:
< rescap : Adequacy Proper noun = "broadFileSystemAccess" /> < uap : Adequacy Name = "removableStorage" /> Whole department should look like below:
< Capabilities > < Capability Proper name = "internetClient" /> < rescap : Capability Name = "broadFileSystemAccess" /> < uap : Adequacy Name = "removableStorage" /> </ Capabilities > Permissions are configured but this is non the end.
Setup permissions in the Windows 10 system
Besides declaration of permissions in the app manifest we take to grant access to the file system in the Windows 10:
Open up "Settings" tab and select "Privacy":
And so select "File system":
In the section "Choose which apps can admission your file system" select the right UWP application:
Afterwards all above steps application will have access to the external file organisation.
Setup surround variable
I mentioned before that path to the file should be stored in the surround variable and UWP application should read it
Open Windows carte du jour and type "surround variable", you should see below:
Now lets add new environemnt variable for the current user. Click "New" button:
Provide the name and the value for the new environment variable. In this case I provided file path and file name with extension:
After clicking on "OK" button, variable should exist displayed on the list:
Update source lawmaking to admission surround variable and file from external system
Now we have to add together the source code to read surround variable value (so the path to the file) and code to access the file content. For this article I created demo which is available on my Github here.
In the "FileService" class in that location is one method - "LoadFileContentUsingPathFromEnvironemntVariable":
public class FileService : IFileService { public async Task < string > LoadFileContentUsingPathFromEnvironemntVariable ( string environmentVariableName ) { if ( cord . IsNullOrEmpty ( environmentVariableName )) { throw new ArgumentNullException ( "Please provide the name of environment variable" ); } var filePathFromEnvironmentVariable = Environment . GetEnvironmentVariable ( environmentVariableName ); if ( string . IsNullOrEmpty ( filePathFromEnvironmentVariable )) { throw new ArgumentNullException ( "Please provide the value of environment variable" ); } var textFileFromExternalPath = look StorageFile . GetFileFromPathAsync ( filePathFromEnvironmentVariable ); var fileContent = await FileIO . ReadTextAsync ( textFileFromExternalPath ); return fileContent ; } } Beginning of all we have to cheque if the proper name of the environment variable is non empty. If it is empty, exception is thrown. The aforementioned for the value. Once file path is loaded from the environs variable we want to access the file content and display it in the app. Start we take to become the file and next nosotros have to read its content. Thats it.
Display file content in the application
Once file content is returned we can display it in the application:
Summary
In this commodity I presented how to set up permissions for the Universal Windows Platform awarding and so it tin access external file system. I also showed how to use environment variables in the source lawmaking.
Source: https://daniel-krzyczkowski.github.io/UWP-External-file-system-access-and-environment-variables/
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