Archive for the ‘C#’ Category

String vs. StringBuilder.

January 7th, 2009

Do you prefer…

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for (_i=0;_i<_max;_i++)
				{
					mString += ", Another String";
				}

rather than…

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				for (_i=0;_i<_max;_i++)
				{
					mStringBuilder.Append(", Another String");
				}

I hope you don’t.

Here is why. The String type is an immutable object type which means that it will create a new string every time it is modified. This will make you pay with your application’s performance when you do long string concatenations. In other hand the StringBuilder is a mutable object type, so it will not create a new StringBuilder every time you modify it. The StringBuilder will create a new buffer only if it reaches its limit if not it will just append the existing one.

I wrote this proof-of-concept application in order to provide you with some performance metrics.

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using System;
 
namespace testStringBuilder
{
	class Program
	{
		public static void Main(string[] args)
		{
 
			int _max = 10000;
			int _i = 0;
 
			double mStringLapse = 0;
			double mStringBuilderLapse = 0;
 
			DateTime mStartTime;
			TimeSpan mLapse;
 
			string mString;
			System.Text.StringBuilder mStringBuilder;
 
			while (_max < 1000000)
			{
 
				mString = "";
				mStringBuilder = new System.Text.StringBuilder("");
 
				mStartTime = DateTime.Now;
				for (_i=0;_i<_max;_i++)
				{
					mString += ", Another String";
				}
				mLapse = DateTime.Now.Subtract(mStartTime);
				mStringLapse = mLapse.TotalMilliseconds;
 
				mStartTime = DateTime.Now;
				for (_i=0;_i<_max;_i++)
				{
					mStringBuilder.Append(", Another String");
				}
				mLapse = DateTime.Now.Subtract(mStartTime);
				mStringBuilderLapse = mLapse.TotalMilliseconds;
 
				_max +=_max;
 
				Console.WriteLine(_i.ToString() + " Concatenations | String=" + mStringLapse.ToString() + "ms StringBuilder=" + mStringBuilderLapse.ToString() + "ms");
			}
 
			Console.Write("Press any key to continue . . . ");
			Console.ReadKey(true);
		}
	}
}

I guess the results are self explanatory.

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int _max = 10000;

2009-01-07_1321

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int _max = 10;

2009-01-07_1407

Tags: , ,
Posted in .NET, C#, MONO | Comments (0)