. NET Type Safety

Type safe means preventing programs from accessing memory outside the bounds of an object's public properties A programming language is type safe when the language defines the behavior for when the programmer treats a value as a type to which it does not belong. Type safety requires that well-typed programs have no unspecified behavior (i.e., their semantics are complete). Languages such as C and C++, which allow programmers to access arbitrary memory locations, are not type safe. An unsafe programming language supports operations (such as accessing arbitrary memory locations), which are not defined in terms of the language semantics. Type safety is a property of the programming language, and not of the programs themselves.

. NET Type Safety

Technorati Tags: .NET Framework, .net CLR, C# .NET, .NET Concepts

Little RegEx Examples in .NET

If you want to use any of the special characters(viz. [,\, ^, $, . , , ?, *, + , (, ) ) as a literal in a regex, you need to escape them with a backslash.

e.g. Dot in the email pattern

\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b

Most regular expression flavors treat the brace { as a literal character, unless it is part of a repetition operator like {2,6}.

Using Character Classes, you can find text with particular set of characters.

e.g. To allow alphanumeric characters and underscores, use [A-Za-z_0-9]*

The only special characters or metacharacters inside a character class are the closing bracket (]), the backslash (\), the caret (^) and the hyphen (-).

Examples

1) Email Regular Expression

\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b

2) HTML Tag matching - Regular Expression

<([A-Z][A-Z0-9]*)[^>]*>(.*?)</\1>

This is very simple example and can't be used in real scenario, as it can't find the nested html tags.

• Match the character "<" literally (this denotes the start of the HTML tag)
• Match the regular expression below and capture its match into backreference number 1 (this is later useful in finding the end html tag)
  • Match a single character out of the list: in the range between A and Z(the first character has to be alphabet-non-numeric)
  • Match a single character out of the list: in the range between A and Z, or in the range between 0 and 9(The second character has to be any alphanumeric)
    • Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
• Match a single character not present in the list: one of the characters ">"
  • (this allows any no. of spaces and attributes within the HTML tag)Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
• Match the character ">" literally(the start tag ends here)
• Match the regular expression below and capture its match into backreference number 2 ((.*?))
  • Match any single character (. will match any single character including new line)
    • Between zero and unlimited times, as few times as possible, expanding as needed (lazy)(* matches it unlimited times and ? stays non-greedy search nature i.e. stop asap)
• Match the characters "</" literally (Above...once </ is found, it will backtrack, and here starts end tag)
• Match the same text as most recently matched by backreference number 1 (It has to find text that was saved as backreference number 1.)
• Match the character ">" literally (now it has to find the end tag ending character >)

3) Do you want to make RegEx for parsing ASP 3.0 Classic style written program/code?

This can help in matching. And it's a beautiful example of using named capture in Regular Expressions

Technorati Tags: RexEx, Regular Expressions, RegEx Examples

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(?<tbefore>.*?)(?<allcode><%(?<equals>=)*\s*(?<code>.*?)%>)(?<endtext>.*)

Here, tbefore name will capture all text before code starting tag <%.

allcode name will capture all code text within <% %> including signs.

code will capture all code within <% %>.

endtext name will capture all text after this code block.