StringBuilder对象

     System.Text.StringBuilder可以动态创建字符串。同String类中一般的字符串不同，动态字符串的字符可以直接修改，在一般的字符串中，修改的总是字符串的拷贝。同时StringBuilder方法效率更高并且提供了更有效的字符串操作能力。

    

/*  Example9_2.cs illustrates the use of StringBuilder objects*/using System;using System.Text;class Example9_2{  public static void DisplayProperties(    string name,    StringBuilder myStringBuilder  )  {    // display the properties for the StringBuilder object    Console.WriteLine(name + ".Length = " +      myStringBuilder.Length);    Console.WriteLine(name + ".Capacity = " +      myStringBuilder.Capacity);    Console.WriteLine(name + ".MaxCapacity = " +      myStringBuilder.MaxCapacity);  }  public static void Main()  {    // create some StringBuilder objects    StringBuilder myStringBuilder = new StringBuilder();    int capacity = 50;    StringBuilder myStringBuilder2 = new StringBuilder(capacity);    int maxCapacity = 100;    StringBuilder myStringBuilder3 =      new StringBuilder(capacity, maxCapacity);    string myString = "To be or not to be";    StringBuilder myStringBuilder4 = new StringBuilder(myString);    int startIndex = 0;    int stringLength = myString.Length;    StringBuilder myStringBuilder5 =      new StringBuilder(myString, startIndex, stringLength, capacity);    // display the StringBuilder objects' properties    DisplayProperties("myStringBuilder", myStringBuilder);    DisplayProperties("myStringBuilder2", myStringBuilder2);    DisplayProperties("myStringBuilder3", myStringBuilder3);    DisplayProperties("myStringBuilder4", myStringBuilder4);    DisplayProperties("myStringBuilder5", myStringBuilder5);    // use the Append() method to append two strings, an int, and a bool    // to myStringBuilder    myStringBuilder.Append(myString);    myStringBuilder.Append(", that is the question ... ");    int myInt = 1234;    myStringBuilder.Append(myInt);    bool myBool = true;    myStringBuilder.Append(myBool);    // use the Append() method to append a character to myStringBuilder    myStringBuilder.Append('z', 5);    // use the Append() method to append a substring to myStringBuilder    myStringBuilder.Append("Here's another string", 0, 4);    // display the contents of myStringBuilder    Console.WriteLine("myStringBuilder = " + myStringBuilder);    // use the AppendFormat() method to add a formatted    // string containing a floating point number to myStringBuilder    float myFloat = 1234.56789f;    myStringBuilder.AppendFormat("{0, 10:f3}", myFloat);    Console.WriteLine("myStringBuilder = " + myStringBuilder);    // use the Insert() method to insert strings into myStringBuilder    myStringBuilder.Insert(6, "friends, ");    myStringBuilder.Insert(22, "Romans, ", 3);    Console.WriteLine("myStringBuilder = " + myStringBuilder);    // use the Remove() method to remove part of myStringBuilder    myStringBuilder.Remove(14, 7);    Console.WriteLine("myStringBuilder = " + myStringBuilder);    // use the Replace() method to replace part of myStringBuilder    myStringBuilder.Replace(',', '?');    Console.WriteLine("myStringBuilder = " + myStringBuilder);    // use the ToString() method to convert myStringBuilder    // to a string    string myString2 = myStringBuilder.ToString();    Console.WriteLine("myString2 = " + myString2);  }}