Call GetDiskFreeSpaceExA from UWP (C#)

Question

I am working on a UWP app (C#, Visual Studio 2019) and I want to find out the total, free for user and free space of C:. In order to do this, I want to call GetDiskFreeSpaceExA (about GetDiskFreeSpaceExA: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getdiskfreespaceexa).

I tried the following:

[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
 [return: MarshalAs(UnmanagedType.Bool)]
 static extern bool GetDiskFreeSpaceExA(string path,
                                        out ulong freeBytesForUser,
                                        out ulong totalNumberOfBytes,
                                        out ulong totalNumberOfFreeBytes);

Then, I call GetDiskFreeSpaceExA:

ulong freeUser;
ulong total;
ulong free;
string pathC= @"C:\"; // also tried with "C:\\" and @"C:\\"
bool success =  GetDiskFreeSpaceExA(pathC,
                                    out freeUser,
                                    out total,
                                    out free);

if(success)
{
     // ...
}

success is always false. Why? How can I find out the space on C: from UWP? I know that there are some C# methods, but I want DLLs.

Thank you!

Answer 1

You could add the broadFileSystemAccess capability in Package.appxmanifest. This is a restricted capability. Access is configurable in Settings > Privacy > File system.

Please refer to the following code.

Package.appxmanifest:

<?xml version="1.0" encoding="utf-8"?>
<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">
……
 <Capabilities>
   <rescap:Capability Name="broadFileSystemAccess" />
   <Capability Name="internetClient" />   
 </Capabilities>

Code behind:

public async void test()
    {

        const String k_freeSpace = "System.FreeSpace";
        const String k_totalSpace = "System.Capacity";

        try
            {
               
                StorageFolder folder = await StorageFolder.GetFolderFromPathAsync("C:\\");
                var props = await folder.Properties.RetrievePropertiesAsync(new string[] { k_freeSpace, k_totalSpace });
                Debug.WriteLine("FreeSpace: " + (UInt64)props[k_freeSpace]);
                Debug.WriteLine("Capacity:  " + (UInt64)props[k_totalSpace]);
            }
            catch (Exception ex)
            {
                Debug.WriteLine(String.Format("Couldn't get info for drive C."));
            }
        
    }