BytesToString.cs

        private static string[] ByteUnits = new string[] { "B", "KB", "MB", "GB", "TB" };
        
        /// <inheritdoc cref="BytesToString(decimal, byte)"/>
        public static string BytesToString(this int? value, byte decimals = 2) => BytesToString((decimal)value, decimals);

        /// <summary>
        /// Display a byte value with units, rounded up to nearest possible size unit.
        /// </summary>
        /// <param name="value">Number of bytes</param>
        /// <param name="decimals">Number of decimal places to show</param>
        /// <returns>The size as a string with units, such as <c>"2.2 MB"</c> or <c>"998.1 KB"</c></returns>
        public static string BytesToString(this decimal? value, byte decimals = 2)
        {
            if (value == null) return null;
            byte i;
            for (i = 0; i < ByteUnits.Length - 1 && value >= 1024; i++) value /= 1024m;
            return $"{Math.Round(value.Value, decimals)} {ByteUnits[i]}";
        }