Regular Expressions Usage in C#

Description 
 
The source code shows how to use Regular Expressions in C#. The code Functions is written for Validation Alphabet, AlphaNumeric, Integer, Postive Integer, Floating point numbers. You just cut copy these functions and use in any program.
 
Explanation of Regular Expressions
 
Regular expressions are used to search specified in the source string.
 
Examples:
 
Pattern#1
  1. Regex objNotNaturalPattern=new Regex("[^0-9]");
Pattern#2  
  1. Regex objNaturalPattern=new Regex("0*[1-9][0-9]*");
Pattern#1 will match for strings other than 0 to 9.^ symbol is used for Specifying not condition.[] brackets if we are to give range values such as 0 - 9 or a-z or A-Z 
 
eg. abc will return true
123 will return false.
 
Pattern#2 will match for string which are Natural Numbers.Natural numbers Are numbers which are always greater than 0.The pattern 0* tells that a natural Number can be prefixed with any number of zero's or no zero's.the next [1-9] tells that it should contain atleast one number from 1 to 9 followed by any numbers of 0-9's
 
Eg. 0007 returns true whereas 00 will return false.
 
Basic things to be understood in RegEx: 
 
"*" matches 0 or more patterns
"?" matches single character
"^" for ignoring matches.
"[]" for searching range patterns.
 
More RegEx patterns in Next Article. 
 
Source Code
  1. // Source Code starts  
  2. using System.Text.RegularExpressions;  
  3. using System;  
  4. /* 
  5. <HowToCompile> 
  6. csc /r:System.Text.RegularExpressions.dll,System.dll Validation.cs  
  7. </HowToComplie> 
  8. */  
  9. class Validation  
  10. {  
  11.     public static void Main()  
  12.     {  
  13.         String strToTest;  
  14.         Validation objValidate = new Validation();  
  15.         Console.Write("Enter a String to Test for Alphabets:");  
  16.         strToTest = Console.ReadLine();  
  17.         if (objValidate.IsAlpha(strToTest))  
  18.         {  
  19.             Console.WriteLine("{0} is Valid Alpha String", strToTest);  
  20.         }  
  21.         else  
  22.         {  
  23.             Console.WriteLine("{0} is not a Valid Alpha String", strToTest);  
  24.         }  
  25.     }  
  26.     // Function to test for Positive Integers.   
  27.     public bool IsNaturalNumber(String strNumber)  
  28.     {  
  29.         Regex objNotNaturalPattern = new Regex("[^0-9]");  
  30.         Regex objNaturalPattern = new Regex("0*[1-9][0-9]*");  
  31.         return !objNotNaturalPattern.IsMatch(strNumber) &&  
  32.         objNaturalPattern.IsMatch(strNumber);  
  33.     }  
  34.     // Function to test for Positive Integers with zero inclusive   
  35.     public bool IsWholeNumber(String strNumber)  
  36.     {  
  37.         Regex objNotWholePattern = new Regex("[^0-9]");  
  38.         return !objNotWholePattern.IsMatch(strNumber);  
  39.     }  
  40.     // Function to Test for Integers both Positive & Negative   
  41.     public bool IsInteger(String strNumber)  
  42.     {  
  43.         Regex objNotIntPattern = new Regex("[^0-9-]");  
  44.         Regex objIntPattern = new Regex("^-[0-9]+$|^[0-9]+$");  
  45.         return !objNotIntPattern.IsMatch(strNumber) && objIntPattern.IsMatch(strNumber);  
  46.     }  
  47.     // Function to Test for Positive Number both Integer & Real   
  48.     public bool IsPositiveNumber(String strNumber)  
  49.     {  
  50.         Regex objNotPositivePattern = new Regex("[^0-9.]");  
  51.         Regex objPositivePattern = new Regex("^[.][0-9]+$|[0-9]*[.]*[0-9]+$");  
  52.         Regex objTwoDotPattern = new Regex("[0-9]*[.][0-9]*[.][0-9]*");  
  53.         return !objNotPositivePattern.IsMatch(strNumber) &&  
  54.         objPositivePattern.IsMatch(strNumber) &&  
  55.         !objTwoDotPattern.IsMatch(strNumber);  
  56.     }  
  57.     // Function to test whether the string is valid number or not  
  58.     public bool IsNumber(String strNumber)  
  59.     {  
  60.         Regex objNotNumberPattern = new Regex("[^0-9.-]");  
  61.         Regex objTwoDotPattern = new Regex("[0-9]*[.][0-9]*[.][0-9]*");  
  62.         Regex objTwoMinusPattern = new Regex("[0-9]*[-][0-9]*[-][0-9]*");  
  63.         String strValidRealPattern = "^([-]|[.]|[-.]|[0-9])[0-9]*[.]*[0-9]+$";  
  64.         String strValidIntegerPattern = "^([-]|[0-9])[0-9]*$";  
  65.         Regex objNumberPattern = new Regex("(" + strValidRealPattern + ")|(" + strValidIntegerPattern + ")");  
  66.         return !objNotNumberPattern.IsMatch(strNumber) &&  
  67.         !objTwoDotPattern.IsMatch(strNumber) &&  
  68.         !objTwoMinusPattern.IsMatch(strNumber) &&  
  69.         objNumberPattern.IsMatch(strNumber);  
  70.     }  
  71.     // Function To test for Alphabets.   
  72.     public bool IsAlpha(String strToCheck)  
  73.     {  
  74.         Regex objAlphaPattern = new Regex("[^a-zA-Z]");  
  75.         return !objAlphaPattern.IsMatch(strToCheck);  
  76.     }  
  77.     // Function to Check for AlphaNumeric.  
  78.     public bool IsAlphaNumeric(String strToCheck)  
  79.     {  
  80.         Regex objAlphaNumericPattern = new Regex("[^a-zA-Z0-9]");  
  81.         return !objAlphaNumericPattern.IsMatch(strToCheck);  
  82.     }  
  83. }  
  84. // Source Code End