C# 4 and .NET 4

examining system.string ❘ 211
Hello from all the guys at Wrox Press.
figure 9-1
39 characters
111 characters
Then, on calling the AppendFormat() method, the remaining text is placed in the empty space, without the
need for more memory allocation. However, the real efficiency gain from using a StringBuilder comes
when you are making repeated text substitutions. For example, if you try to encrypt the text in the same
way as before, you can perform the entire encryption without allocating any more memory whatsoever:
StringBuilder greetingBuilder =
new StringBuilder("Hello from all the guys at Wrox Press. ", 150);
greetingBuilder.AppendFormat("We do hope you enjoy this book as much as we " +
"enjoyed writing it");
Console.WriteLine("Not Encoded:\n" + greetingBuilder);
for(int i = 'z'; i>='a'; i--)
{
char old1 = (char)i;
char new1 = (char)(i+1);
greetingBuilder = greetingBuilder.Replace(old1, new1);
}
for(int i = 'Z'; i>='A'; i--)
{
char old1 = (char)i;
char new1 = (char)(i+1);
greetingBuilder = greetingBuilder.Replace(old1, new1);
}
Console.WriteLine("Encoded:\n" + greetingBuilder);
This code uses the StringBuilder.Replace() method, which does the same thing as String.Replace(),
but without copying the string in the process. The total memory allocated to hold strings in the preceding
code is 150 characters for the StringBuilder instance, as well as the memory allocated during the string
operations performed internally in the final Console.WriteLine() statement.
Normally, you want to use StringBuilder to perform any manipulation of strings and String to store or
display the final result.
stringbuilder members
You have seen a demonstration of one constructor of StringBuilder, which takes an initial string and
capacity as its parameters. There are others. For example, you can supply only a string:
StringBuilder sb = new StringBuilder("Hello");
Or you can create an empty StringBuilder with a given capacity:
StringBuilder sb = new StringBuilder(20);
Apart from the Length and Capacity properties, there is a read-only MaxCapacity property that indicates
the limit to which a given StringBuilder instance is allowed to grow. By default, this is given by int
.MaxValue (roughly two billion, as noted earlier), but you can set this value to something lower when you
construct the StringBuilder object:
// This will both set initial capacity to 100, but the max will be 500.
// Hence, this StringBuilder can never grow to more than 500 characters,
// otherwise it will raise exception if you try to do that.
StringBuilder sb = new StringBuilder(100, 500);
www.it-ebooks.info