c# for dummies: c sharp programming

c# for dummies: c sharp programming: String equality comparison Despite ordinal’s  limitations,  string’s  == operator  always performs  ordinal  case- sensitive comparison. The...

c sharp programming

String equality comparison


Despite ordinal’s  limitations,  string’s  == operator  always performs  ordinal  case-
sensitive comparison. The same goes for the instance version of string.Equals when
called without arguments; this defines the “default” equality comparison behavior
for the string type.
The ordinal algorithm was chosen  for string’s == and Equals
functions because  it’s both highly  efficient  and  deterministic.
String  equality  comparison  is  considered  fundamental  and  is
performed far more frequently than order comparison.
A “strict” notion of equality is also consistent with the general
use of the == operator.


The following methods allow culture-aware or case-insensitive comparisons:
public bool Equals(string value, StringComparison comparisonType);
public static bool Equals (string a, string b,
                           StringComparison comparisonType);
The static version is advantageous in that it still works if one or both of the strings
are null. StringComparison is an enum defined as follows:


The static version is advantageous in that it still works if one or both of the strings
are null. StringComparison is an enum defined as follows:
public enum StringComparison
{
  CurrentCulture,               // Case-sensitive
  CurrentCultureIgnoreCase,
  InvariantCulture,             // Case-sensitive
  InvariantCultureIgnoreCase,
  Ordinal,                      // Case-sensitive
  OrdinalIgnoreCase
}


For example:
Console.WriteLine (string.Equals ("foo", "FOO",
                   StringComparison.OrdinalIgnoreCase));   // True
Console.WriteLine ("?" == "u");                            // False
Console.WriteLine (string.Equals ("?", "u",
                   StringComparison.CurrentCulture));      // ?
(The result of the final comparison is determined by the computer’s current language
settings.)

c# for dummies: StringBuilder in c#

c# for dummies: StringBuilder in c#: StringBuilder The StringBuilder class (System.Text namespace) represents a mutable (editable) string. With a StringBuilder, you can Append, ...

StringBuilder in c#

StringBuilder



The StringBuilder class (System.Text namespace) represents a mutable (editable)
string. With a StringBuilder, you can Append, Insert, Remove, and Replace substrings
without replacing the whole StringBuilder.
StringBuilder’s constructor optionally accepts an  initial string value, as well as a
starting size for its internal capacity (default is 16 characters). If you go above this,
StringBuilder  automatically  resizes  its  internal  structures  to  accommodate  (at  a
slight performance cost) up to its maximum capacity (default is int.MaxValue).
A popular use of StringBuilder  is to build up a  long string by repeatedly calling
Append. This approach is much more efficient than repeatedly concatenating ordi-
nary string types:
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 50; i++) sb.Append (i + ",");
To get the final result, call ToString():
Console.WriteLine (sb.ToString());

0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,
27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,

In our example, the expression i + "," means that we’re still
repeatedly concatenating strings. However,  this  incurs only a
small performance cost in that the strings in question are small
and don’t grow with each  loop  iteration. For maximum per-
formance, however, we could change the loop body to this:
{ sb.Append (i.ToString()); sb.Append (","); }
AppendLine performs an Append that adds a new line sequence ("\r\n" in Windows).
AppendFormat accepts a composite format string, just like String.Format.
As well  as  the  Insert,  Remove,  and  Replace methods  (Replace  functions  such  as
string’s Replace), StringBuilder defines a Length property and a writable indexer for
getting/setting individual characters.
To  clear  the  contents of  a  StringBuilder,  either  instantiate  a new one or  set  its
Length to zero.


Setting a StringBuilder’s Length to zero doesn’t shrink  its  in-
ternal capacity. So, if the StringBuilder previously contained 1
million characters, it will continue to occupy around 2 MB of
memory after zeroing its Length. If you want to release the mem-
ory, you must create a new StringBuilder and allow the old one
to drop out of scope (and be garbage-collected).

c# for dummies: c sharp programming

c# for dummies: c sharp programming: String order comparison String’s CompareTo instance method performs culture-sensitive, case-sensitive order comparison. Unlike the == operat...

c sharp programming

String order comparison



String’s CompareTo instance method performs culture-sensitive, case-sensitive order
comparison. Unlike the == operator, CompareTo does not use ordinal comparison: for
ordering, a culture-sensitive algorithm is much more useful.
Here’s the method’s definition:
public int CompareTo (string strB);
The  CompareTo  instance  method  implements  the  generic
IComparable  interface,  a  standard  comparison  protocol  used
across  the  .NET  Framework. This means  string’s  CompareTo
defines the default ordering behavior strings,  in such applica-
tions as sorted collections, for instance. For more information


For other kinds of comparison, you can call the static Compare and CompareOrdinal
methods:
public static int Compare (string strA, string strB,
                           StringComparison comparisonType);
public static int Compare (string strA, string strB, bool ignoreCase,
                           CultureInfo culture);
public static int Compare (string strA, string strB, bool ignoreCase);
public static int CompareOrdinal (string strA, string strB);
The last two methods are simply shortcuts for calling the first two methods.
All of the order comparison methods return a positive number, a negative number,
or zero, depending on whether the first value comes after, before, or alongside the
second value:
Console.WriteLine ("Boston".CompareTo ("Austin"));    // 1
Console.WriteLine ("Boston".CompareTo ("Boston"));    // 0
Console.WriteLine ("Boston".CompareTo ("Chicago"));   // -1
Console.WriteLine ("?".CompareTo ("u"));              // 0
Console.WriteLine ("foo".CompareTo ("FOO"));          // -1


The following performs a case-insensitive comparison using the current culture:
Console.WriteLine (string.Compare ("foo", "FOO", true));   // 0
By supplying a CultureInfo object, you can plug in any alphabet:
// CultureInfo is defined in the System.Globalization namespace
CultureInfo german = CultureInfo.GetCultureInfo ("de-DE");
int i = string.Compare ("Müller", "Muller", false, german);

c# for dummies: c sharp programming

c# for dummies: c sharp programming: Ordinal versus culture comparison There are two basic algorithms for string comparison: ordinal and culture-sensitive. Ordinal  comparisons ...