RegEx - Numbers matching. Below is a sample code to find the existence of integers within a string.

Transcription

1 RegEx - Numbers matching Below is a sample code to find the existence of integers within a string. Sample code pattern to check for number in a string: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Regex_FirstExample class Program static void Main(string[] args) string number = " "; // number to check string pattern // pattern to check System.Console.WriteLine("The number is : " + number); System.Console.WriteLine("The pattern string is : " + pattern); if (System.Text.RegularExpressions.Regex.IsMatch(number, pattern)) // regex to validate the number

2 System.Console.WriteLine(" The given number is a valid pattern"); else System.Console.WriteLine(" The given number is an invalid pattern"); // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey();

3 Code Explanation: The libraries are imported by default in C# class file. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;

4 Here System is the parent library for C# code. Collections.Generic allow to generate strongly typed collections for better performance. The System.Text namespace is a holder for classes to represent ASCII and Unicode character encodings. RegularExpressions class is a child class of System.Text namespace. The code namespace Regex_FirstExample defines a holder to contain one or more class. Here it contains a class named Program. The line of code static void Main(string[] args) defines a static method called Main, whose elements can be called without an instance. It contains a string array as parameter, to receive input from the console window. The lines of code below declare two string variables, one with a string of numbers and other with a string pattern to find a number within that string as follows: string number = " "; // number to check string pattern // pattern to check Now the pattern string is checked against the string of numbers and if the check satisfies, a message is shown at the console as The given number is a valid pattern else The given number is an invalid pattern. This is done by the following lines of code:

5 if(system.text.regularexpressions.regex.ismatch(number, pattern)) // regex to validate the number System.Console.WriteLine(" The given number is a valid pattern"); else System.Console.WriteLine(" The given number is an invalid pattern"); Output: The string pattern \d checks whether the string " " contains numbers. Since the check is

6 satisfied the output is displayed as The given number is a valid pattern. Matching Mobile Number: To find the exact numbers given in a set of number, for instance to validate the 10-digit Indian mobile number the pattern would be The pattern to match a sequence of ten successive digits within a string

7 Sample code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Regex_FirstExample class Program static void Main(string[] args) string number = " "; // number to check string pattern // pattern to check System.Console.WriteLine("The number is : " + number); System.Console.WriteLine("The pattern string is : " + pattern); if (System.Text.RegularExpressions.Regex.IsMatch(number, pattern)) // regex to validate the number System.Console.WriteLine(" The given number is a valid pattern");

8 else System.Console.WriteLine(" The given number is an invalid pattern"); // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey(); Code Explanation:

9 The lines of code below declare two string variables, one with a string of numbers and other with a string pattern to find a number within that string as follows: string number = " "; // number to check string pattern // pattern to check Now the pattern string is checked against the string of numbers and if the check satisfies, a message is shown at the console as The given number is a valid pattern else The given number is an invalid pattern. This is done by the following lines of code: if (System.Text.RegularExpressions.Regex.IsMatch(number, pattern)) // regex to validate the number System.Console.WriteLine(" The given number is a valid pattern"); else System.Console.WriteLine(" The given number is an invalid pattern");

10 Output: The string pattern "^\d10$" checks whether the string " " contains only 10 digit number. This is ensured step by step as follows: a. d10 ensures only 10 digits. b. ^\d10 ensures that 10 digits match at the start position of the string. c. ^\d10$ - ensures that 10 digits match at the start positon and also at the end position, which means that the string should contain only a 10-digit number. Since the check is satisfied the output is displayed as The given number is a valid pattern. Now an alphabet is added into the number variable as follows: string number = "a "; string pattern // number to check // pattern to check

11 The output is : The given number is an invalid pattern. Now its time to try with less number of numbers. The total numbers are 9. string number = " "; // number to check string pattern // pattern to check The output is : The given number is an invalid pattern.