Regular expression C#

C# > Text > Regular expression

A regular expression is a pattern. The engine try to find matches in input text using this pattern.
A pattern contains character literals, operators and constructs.

• IsMatch
• Split

System.Text namespaces C#

C# > Text

Text in  C# defines types for character encoding and string manipulation

• Regular expression
• StringBuilder

Regex IsMatch method

C# > Text > RegularExpressions > IsMatch

Regex IsMatch method indicates whether the regular expression specified finds a match in a specified input string.

Example:

string[] partNumbers = { "1298-6736","343434" };

Regex rgx = new Regex(@"^[a-zA-Z0-9-]*-[a-zA-Z0-9]*$");

foreach (string partNumber in partNumbers)
   if (rgx.IsMatch(partNumber))
     MessageBox.Show  (partNumber);

Pattern

^                      begin the match at the beginning of the line.
[a-zA-Z0-9]    match a single alphabetic character (a through z or A through Z) or numeric character. -                      match a hyphen
*                      must be zero or more of these characters
$                      end the match at the end of the line

Convert color to html color C#

C# > Color

ColorTranslator.ToHtml translates the specified Color structure to an HTML string color.

Example:

Color cl = Color.FromArgb(0, 99, 148);

string htmlColor = ColorTranslator.ToHtml(cl);

Get Oracle Version

Oracle > Version

V$VERSION displays version numbers of core library components in the Oracle Database.

Example:

select * from v$version

Result:

Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

Sealed modifier C#

C# > Modifiers > sealed

Sealed modifier prevents other classes from inheriting from it.
Also you can use the sealed modifier on a method or property that overrides a virtual method or property in a base class. This enables you to allow classes to derive from your class and prevent them from overriding specific virtual methods or properties.

Examples

1. Sealed class
    class C1 { }
    sealed class C2 : C1 { }
    class C3 : C2 { } // Error : cannot derive from sealed type C2

2. Sealed method

    class A

    {
        protected virtual void F() { }
        protected virtual void F1() { }
    }
    class B : A
    {
        sealed protected override void F() { }
        protected override void F1() { }
    }
    class C : B
    {
        protected override void F() { } //Error cannot override inherited member because it is sealeD
        protected override void F1() { }
    }

const c#

C# > Modifiers > const

The const specifies that the value of the field or the local variable is constant and it cannot be modified.
 
The const keyword differs from the readonly keyword. A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor.

Example:

class SampleConst
    {
        public int x;
        public int y;
        public const int c1 = 1;
        public const int c2 = c1 + 5;

        public SampleConst(int v1)

        {
            x = v1 + c1;
            y = x + c2;
        }
    }