System.String A string is a sequential collection of Unicode characters that is used to represent text. A String object is a sequential collection of System.Char objects that represent a string. The value of the String object is the content of the sequential collection, and that value is immutable. A String object is called immutable (read-only) because its value cannot be modified once it has been created.
Some Methods in System.StringName DescriptionClone Returns a reference to this instance of String. Compares two specified String objects and returnsCompare(String, an integer that indicates their relative position in theString) sort order. Creates the string representation of a specifiedConcat(Object) object. Creates a new instance of String with the sameCopy value as a specified String. Returns a value indicating whether the specifiedContains String object occurs within this string. Determines whether this instance and a specifiedEquals(Object) object, which must also be a String object, have the same value. Replaces the format item in a specified string withFormat(String,
Building Strings String is an extremely powerful class that implements a large number of very useful methods. However, the String class has a short coming that makes it very inefficient for making repeated modifications to given string. For example, when you write fallowing code, the compiler actually creates a new string object to hold the new sequence of characters, and that new object is assigned to b. The string "h" is then eligible for garbage collection. Example: string b = "h"; b += "ello";
StringBuilder Class Represents a mutable string of characters. This class cannot be inherited. Namespace is System.Test This class represents a string-like object whose value is a mutable sequence of characters. The value is said to be mutable because it can be modified once it has been created by appending, removing, replacing, or inserting characters. For Example: StringBuilder text=new StringBuilder (“….String …”,size);//size is an integer Text.AppendForamt(“New String….”); This code sets an initial capacity of size for StringBuilder
StringBuilder MembersName DescriptionAppend() Appends a string to the current string.AppendFormat() Appends a string that has been worked out from a format specifierInsert() Inserts a sub string into the current stringRemove() Removes characters from the current string.Replace() Replaces all occurrences of a character with another character or a substring with another substring in the current string.ToString() Returns the current string cast to a System.String object.
Format Strings Standard numeric format strings are used to format common numeric types. A standard numeric format string takes the form Axx, where A is an alphabetic character called the format specifier, and xx is an optional integer called the precision specifier. The precision specifier ranges from 0 to 99 and affects the number of digits in the result. Any numeric format string that contains more than one alphabetic character, including white space, is interpreted as a custom numeric format string.
Format StringsSPECIFIE APPLIES TO MEANING EXAMPLERC Numeric types Locale-specific $4834.50(US) monetary value £4834.50(UK)D Integer types General integer 4834 onlyE Numeric types Scientific notation 4.384E+003F Numeric types Fixed decimal 4834.50G Numeric types General number 4834.5N Numeric types Common locale- 4,384.50(UK/USA) specific format for 4 384,50(continental numbers Europep Numeric types Percentage notation 432,000.00%X Integer types Hexadecimal format 1120(if you want to only display 0x1120, you will
Regular Expressions Regular expressions provide a powerful, flexible, and efficient method for processing text. The extensive pattern-matching notation of regular expressions enables you to quickly parse large amounts of text to find specific character patterns; to validate text to ensure that it matches a predefined pattern (such as an e-mail address); to extract, edit, replace, or delete text substrings; and to add the extracted strings to a collection in order to generate a report. For many applications that deal with strings or that parse large blocks of text, regular expressions are an indispensable tool.
Regular Expressions Regular expressions are part of those small technology areas that are incredibly useful in a wide range of programs, yet rarely used among developers. You can think regular expressions as a mini- programming language with one specific scope: to locate substrings within a large string expression.
How Regular Expressions Work The centerpiece of text processing with regular expressions is the regular expression engine, which is represented by the System.Text.RegularExpressions.Regex object in the .NET Framework. At a minimum, processing text using regular expressions requires that the regular expression engine be provided with the following two items of information: The regular expression pattern to identify in the text. The text to parse for the regular expression pattern.
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