file size

Here is a function that uses recursion (Hidden in the LINQ statement) to calculate the size of a given directory:

// Usage: GetDirectorySize("C:/");
public static long GetDirectorySize(string path)
{
    return GetDirectorySize(new DirectoryInfo(path));
}

public static long GetDirectorySize(DirectoryInfo directoryInfo)
{
    // Calculate the size of all files in the current directory
    var sizeOfFiles = directoryInfo.GetFiles().Sum(fileInfo => fileInfo.Length);

    // Now calculate the size of each child directory, and sum them to get the size of child directories
    var sizeOfDirectories = directoryInfo.GetDirectories().Select(GetDirectorySize).Sum();

    // The size of a directory is the size of its files + the size of child directories
    return sizeOfFiles + sizeOfDirectories;
}

Using this you can simply supply the path as either a DirectoryInfo object or as a string.

Well if i use this: c:/users... It gives me an error: no acces to this location..

So don't think this is works.

Also i can just use driveinfo if the user selected like: C:/..

I only need to use directoryinfo if the selected location is a subfolder..

The program either needs to be ran as an Administrator, or you can add exception handling to prevent the program from crashing. I suggest adding exception handling to your code regardless.

If you want to use the values from DriveInfo then you can check if the directory path is the same as a drive, if so return the size.