getting free space tries to get the space safely, if doesn't work and windows

the tries interop.

NzbDrone.Common/DiskProvider.cs

@@ -200,21 +200,49 @@ namespace NzbDrone.Common
             File.SetAccessControl(filename, fs);
         }
 
-        public virtual ulong GetAvilableSpace(string path)
+        public virtual long GetAvilableSpace(string path)
         {
             if (!FolderExists(path))
                 throw new DirectoryNotFoundException(path);
 
-            ulong freeBytesAvailable;
-            ulong totalNumberOfBytes;
-            ulong totalNumberOfFreeBytes;
 
-            bool success = GetDiskFreeSpaceEx(path, out freeBytesAvailable, out totalNumberOfBytes,
+            var driveInfo = DriveInfo.GetDrives().SingleOrDefault(c => c.IsReady && c.Name.Equals(Path.GetPathRoot(path), StringComparison.CurrentCultureIgnoreCase));
-                               out totalNumberOfFreeBytes);
-            if (!success)
-                throw new System.ComponentModel.Win32Exception();
 
-            return freeBytesAvailable;
+            if (driveInfo == null)
+            {
+                if (EnvironmentProvider.IsLinux)
+                {
+                    return 0;
+                }
+             
+                return DriveFreeSpaceEx(path);
+            }
+
+            return driveInfo.AvailableFreeSpace;
+        }
+
+        private static long DriveFreeSpaceEx(string folderName)
+        {
+            if (string.IsNullOrEmpty(folderName))
+            {
+                throw new ArgumentNullException("folderName");
+            }
+
+            if (!folderName.EndsWith("\\"))
+            {
+                folderName += '\\';
+            }
+
+            ulong free = 0;
+            ulong dummy1 = 0;
+            ulong dummy2 = 0;
+
+            if (GetDiskFreeSpaceEx(folderName, out free, out dummy1, out dummy2))
+            {
+                return (long)free;
+            }
+
+            return 0;
         }
 
         public virtual string ReadAllText(string filePath)

NzbDrone.Common/PathExtensions.cs

@@ -31,7 +31,7 @@ namespace NzbDrone.Common
             return info.FullName.TrimEnd('/').Trim('\\', ' ');
         }
 
-        static string GetProperDirectoryCapitalization(DirectoryInfo dirInfo)
+        private static string GetProperDirectoryCapitalization(DirectoryInfo dirInfo)
         {
             var parentDirInfo = dirInfo.Parent;
             if (null == parentDirInfo)
@@ -40,7 +40,7 @@ namespace NzbDrone.Common
                                 parentDirInfo.GetDirectories(dirInfo.Name)[0].Name);
         }
 
-        static string GetProperFilePathCapitalization(string filename)
+        public static string GetActualCasing(this string filename)
         {
             var fileInfo = new FileInfo(filename);
             DirectoryInfo dirInfo = fileInfo.Directory;

NzbDrone.Core.Test/ProviderTests/DiskProviderTests/FreeDiskSpaceTest.cs

@@ -13,10 +13,18 @@ namespace NzbDrone.Core.Test.ProviderTests.DiskProviderTests
         public void should_return_free_disk_space()
         {
             var result = Subject.GetAvilableSpace(Directory.GetCurrentDirectory());
+            result.Should().BeGreaterThan(0);
+        }
+
+        [Test]
+        public void should_be_able_to_get_space_on_unc()
+        {
+            WindowsOnly();
 
-            //Checks to ensure that the free space on the first is greater than 0 (It should be in 99.99999999999999% of cases... I hope)
+            var result = Subject.GetAvilableSpace(@"\\localhost\c$\Windows");
             result.Should().BeGreaterThan(0);
         }
+
         [Test]
         public void should_throw_if_drive_doesnt_exist()
         {

NzbDrone.Core/RootFolders/RootFolder.cs

@@ -8,7 +8,7 @@ namespace NzbDrone.Core.RootFolders
     {
         public string Path { get; set; }
 
-        public ulong FreeSpace { get; set; }
+        public long FreeSpace { get; set; }
 
         public List<UnmappedFolder> UnmappedFolders { get; set; }
     }

NzbDrone.Core/RootFolders/RootFolderService.cs

@@ -15,7 +15,7 @@ namespace NzbDrone.Core.RootFolders
         RootFolder Add(RootFolder rootDir);
         void Remove(int id);
         List<UnmappedFolder> GetUnmappedFolders(string path);
-        Dictionary<string, ulong> FreeSpaceOnDrives();
+        Dictionary<string, long> FreeSpaceOnDrives();
         RootFolder Get(int id);
     }
 
@@ -99,9 +99,9 @@ namespace NzbDrone.Core.RootFolders
             return results;
         }
 
-        public virtual Dictionary<string, ulong> FreeSpaceOnDrives()
+        public virtual Dictionary<string, long> FreeSpaceOnDrives()
         {
-            var freeSpace = new Dictionary<string, ulong>();
+            var freeSpace = new Dictionary<string, long>();
 
             var rootDirs = All();