stringとstringBuilderのパフォーマンスの違い

自分でテストしましたが、性能の差はまだ大きいです.

Console.WriteLine("Class String:");
string strClass = string.Empty;
DateTime BeginTime = System.DateTime.Now;
Console.WriteLine(BeginTime.ToString());
for (int i = 0; i <= 99999; i++)
{
    strClass += i.ToString();
}
DateTime EndTime = System.DateTime.Now;
Console.WriteLine(EndTime.ToString());
TimeSpan ts = EndTime.Subtract(BeginTime);
Console.WriteLine("class string cost time is:" + ts.TotalMilliseconds.ToString() + "ms");
Console.WriteLine(); Console.WriteLine("Class StringBulid:");
StringBuilder sb = new StringBuilder();
Console.WriteLine(System.DateTime.Now.ToString());
BeginTime = System.DateTime.Now;
for (int i = 0; i <= 99999; i++)
{
    sb.Append(i.ToString());
}
Console.WriteLine(System.DateTime.Now.ToString());
EndTime = System.DateTime.Now;
ts = EndTime.Subtract(BeginTime);
Console.WriteLine("class stringbuild cost time is:" + ts.TotalMilliseconds.ToString() + "ms");

結果:Class String:2008-12-24 13:33:29 2008-12-24 13:34:29 class string cost time is:60453.125 ms Class StringBulid:2008-12-24 13:34:29 2008-12-24 13:34:29 class stringbuild cost time is:32.25 ms任意のキーで続行してください.