System.IO.DriveInfo.NormalizeDriveName C# (CSharp) Method

        private static string NormalizeDriveName(string driveName)
        {
            Debug.Assert(driveName != null);

            string name;

            if (driveName.Length == 1)
                name = driveName + ":\\";
            else
            {
                // GetPathRoot does not check all invalid characters
                if (PathInternal.HasIllegalCharacters(driveName))
                    throw new ArgumentException(SR.Format(SR.Arg_InvalidDriveChars, driveName), nameof(driveName));

                name = Path.GetPathRoot(driveName);
                // Disallow null or empty drive letters and UNC paths
                if (name == null || name.Length == 0 || name.StartsWith("\\\\", StringComparison.Ordinal))
                    throw new ArgumentException(SR.Arg_MustBeDriveLetterOrRootDir);
            }
            // We want to normalize to have a trailing backslash so we don't have two equivalent forms and
            // because some Win32 API don't work without it.
            if (name.Length == 2 && name[1] == ':')
            {
                name = name + "\\";
            }

            // Now verify that the drive letter could be a real drive name.
            // On Windows this means it's between A and Z, ignoring case.
            char letter = driveName[0];
            if (!((letter >= 'A' && letter <= 'Z') || (letter >= 'a' && letter <= 'z')))
                throw new ArgumentException(SR.Arg_MustBeDriveLetterOrRootDir);

            return name;
        }