Get Sift3 distance from two words. Simmilar to the Levenshtein distance, but it's four time faster. Verifying that(http://norvig.com/ngrams/) data sets.

Sift3Distance.cs

		/// <summary>
		/// Get Sift3 distance from two words.
		/// (eg: spell checking)
		/// </summary>
		/// <param name="source"> source string </param>
		/// <param name="actual"> actual string </param>
		/// <param name="maxOffset"> max offset </param>
		/// <returns> The distance of the two words. </returns>
		public static float GetSift3Distance(string source, string actual, int maxOffset)
		{
			if (string.IsNullOrEmpty(source))
			{
				return string.IsNullOrEmpty(actual) ? 0 : actual.Length;
			}

			if (string.IsNullOrEmpty(actual))
			{
				return source.Length;
			}

			int c = 0;
			int offset1 = 0;
			int offset2 = 0;
			int lcs = 0;
			while ((c + offset1 < source.Length) && (c + offset2 < actual.Length))
			{
				if (source[c + offset1] == actual[c + offset2])
				{
					lcs++;
				}
				else
				{
					offset1 = 0;
					offset2 = 0;
					for (int i = 0; i < maxOffset; i++)
					{
						if ((c + i < source.Length) && (source[c + i] == actual[c]))
						{
							offset1 = i;
							break;
						}

						if ((c + i < actual.Length) && (source[c] == actual[c + i]))
						{
							offset2 = i;
							break;
						}
					}
				}

				c++;
			}

			return ((source.Length + actual.Length) / 2) - lcs;
		}