Calling Win32 API from .NET C# Application

As quoted in the useful reference below:

"Anybody doing any serious Windows development in C# will probably end up calling many Win32 functions. The .NET framework just doesn't cover 100% of the Win32 API." - Mike Thompson

This illustrative example here is simply to show what the integrated code looks like; however identifying available drive space is a common app requirement

The interop of .NET and Win32API works by way of referencing the InteropServices .NET namespace and using normal Win32 API functions with the [DllImport()] attribute denoting the Win32 API assembly being used and the corresponding function being modified as "static extern" which informs the compiler that the function is calling unmanaged (non-.NET) code.

 using System;  
 using System.Runtime.InteropServices;  
 namespace ConsoleApp1  
 {  
   internal static class Win32  
   {  
     [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]  
     internal static extern bool GetDiskFreeSpaceEx(string drive, out long freeBytesForUser, out long totalBytes, out long freeBytes);  
   }  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       long freeBytesForUser;  
       long totalBytes;  
       long freeBytes;  
       Console.WriteLine("Free space in this directory:");  
       if (Win32.GetDiskFreeSpaceEx(@"C:\", out freeBytesForUser, out totalBytes, out freeBytes))  
       {  
         Console.WriteLine("Free user bytes: " + freeBytesForUser.ToString());  
         Console.WriteLine("Free total bytes: " + totalBytes.ToString());  
         Console.WriteLine("Free bytes: " + freeBytes.ToString());  
       }  
       Console.ReadLine();  
     }  
   }  
 }  

Reference: https://stackoverflow.com/questions/137255/how-can-i-determine-if-a-remote-drive-has-enough-space-to-write-a-file-using-c