本文探讨了C#中字符串(String)与可变字符串(StringBuilder)的区别，对比了两者在字符串拼接时的性能表现，并介绍了装箱与拆箱的概念及其对性能的影响。
/*
Author: Jiangong SUN
*/
1) String vs StringBuilder
System.String is immutable(unchangeable).
System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
StringBuilder is more performant.
When you do string concatenation, like
string str = str1 + str2 + str3;
The C# + concatenation operator builds a new string and causes reduced performance when it concatenates large amounts of text.
However, the .NET Framework includes a StringBuilder class that is optimized for string concatenation. It provides the same benefits as using a character array in C/C++, as well as automatically growing the buffer size (if needed) and tracking the length for you.
2) compare string length
3) boxing and unboxing ( performance costly)
boxing: convert value type to reference type
unboxing: convert reference type to value type
It's better not using boxing and unboxing because it impact the performance.
references:
http://support.microsoft.com/kb/306822/en-us
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