Question : How to compress a string into a short representation in ASP.NET using C# or VB.NET?

We have a need to compress a string into a representation that is shorter than the original string then to decompress it. I wanted to know if there is a way to do this in .NET for strings that are about 200-500 characters (not extremely long, but we need to compress them for use in a URL/querystring).

Answer : How to compress a string into a short representation in ASP.NET using C# or VB.NET?

Because these compression methods result in binary data, and you can't pass bytes in a URL, the compressed data needs to be encoded as a Base64 string. While the compression might reduce the size of the string, I suspect the Base64 encoding is likely to get you a string larger than the one you were trying to compress in the first place - particularly if your string is largely random.

Small data sets, e.g. a 500-byte string, tend to not compress well and often result in an increase in size.

What is contained in your string?

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.IO.Compression;

namespace ConsoleApplication1
{
	class Program
	{
		static void Main(string[] args)
		{
			string longString = GetLongString(500);
			
			string compressed = StringCompressor.CompressString(longString);
			string uncompressed = StringCompressor.DecompressString(compressed);

			Console.WriteLine("Original string length: {0}\r\nCompressed string length: {1}",
				longString.Length, compressed.Length);
			Console.ReadKey();
		}

		static string GetLongString(int len)
		{
			StringBuilder str = new StringBuilder();
			Random rand = new Random(DateTime.Now.Millisecond);

			for (int i = 0; i < len; i++)
				str.Append((char)rand.Next(65, 91));

			return str.ToString();
		}
	}

	public static class StringCompressor
	{
		public static string CompressString(string Input)
		{
			byte[] inputBytes = Encoding.ASCII.GetBytes(Input);
			byte[] outputBytes;

			using (MemoryStream outputStream = new MemoryStream())
			{
				using (GZipStream compressionStream = new GZipStream(outputStream, CompressionMode.Compress, true))
				{
					compressionStream.Write(inputBytes, 0, inputBytes.Length);
				}
				outputBytes = new byte[outputStream.Length];
				outputStream.Position = 0;
				outputStream.Read(outputBytes, 0, outputBytes.Length);
			}

			return Convert.ToBase64String(outputBytes);
		}

		public static string DecompressString(string Input)
		{
			byte[] inputBytes = Convert.FromBase64String(Input);
			byte[] outputBytes;


			using (MemoryStream inputStream = new MemoryStream())
			{
				inputStream.Write(inputBytes, 0, inputBytes.Length);
				inputStream.Position = 0;
				using (GZipStream outputStream = new GZipStream(inputStream, CompressionMode.Decompress))
				{
					outputBytes = GetAllBytes(outputStream);
				}
			}
			return Encoding.ASCII.GetString(outputBytes);
		}

		static byte[] GetAllBytes(Stream stream)
		{
			const int buffer_size = 1024;
			byte[] buffer = new byte[buffer_size];
			List<byte> streamBytes = new List<byte>();

			if (stream.CanSeek)
				stream.Position = 0;

			int bytesRead = 0;
			do
			{
				bytesRead = stream.Read(buffer, 0, buffer_size);
				if (bytesRead > 0)
					streamBytes.AddRange(buffer.Take(bytesRead));
			} while (bytesRead > 0);

			return streamBytes.ToArray();
		}
	}
}