Examples of regular expressions in C #

Regular using System.Text.RegularExpressions;
Using System;


Class Validation
{
public static void Main ()
{
String strtotest;
Validation objvalidate=new Validation ();

Console.Write ("Enter a String to Test for alphabets:");
Strtotest=console.readline ();
if (Objvalidate.isalpha (strtotest))
{
Console.WriteLine ("{0} is Valid Alpha String", strtotest);
}
Else
{
Console.WriteLine ("{0} is not a Valid Alpha String", strtotest);
}
}

Function to test for Positive integers.

public bool Isnaturalnumber (String strnumber)
{
Regex objnotnaturalpattern=new Regex ("[^0-9]");
Regex objnaturalpattern=new Regex ("0*[1-9][0-9]*");

Return!objnotnaturalpattern.ismatch (Strnumber) &&
Objnaturalpattern.ismatch (Strnumber);
}

Function to test for Positive integers with zero inclusive

public bool Iswholenumber (String strnumber)
{
Regex objnotwholepattern=new Regex ("[^0-9]");

Return!objnotwholepattern.ismatch (Strnumber);
}

Function to Test for integers both Positive & Negative

public bool Isinteger (String strnumber)
{
Regex objnotintpattern=new Regex ("[^0-9-]");
Regex objintpattern=new Regex ("^-[0-9]+$|^[0-9]+$");

Return!objnotintpattern.ismatch (Strnumber) &&
Objintpattern.ismatch (Strnumber);
}

Function to Test for Positive number both integers & real

public bool Ispositivenumber (String strnumber)
{
Regex objnotpositivepattern=new Regex ("[^0-9.]");
Regex objpositivepattern=new Regex ("^[.] [0-9]+$| [0-9]*[.] *[0-9]+$ ");
Regex objtwodotpattern=new Regex ("[0-9]*[.] [0-9]*[.] [0-9]* ");

Return!objnotpositivepattern.ismatch (Strnumber) &&
Objpositivepattern.ismatch (Strnumber) &&
!objtwodotpattern.ismatch (Strnumber);
}

Function to test whether of the string is valid number or not
public bool Isnumber (String strnumber)
{
Regex objnotnumberpattern=new Regex ("[^0-9.-]");
Regex objtwodotpattern=new Regex ("[0-9]*[.] [0-9]*[.] [0-9]* ");
Regex objtwominuspattern=new Regex ("[0-9]*[-][0-9]*[-][0-9]*");
String strvalidrealpattern= "^" ([-]|[.]| [-.]| [0-9]) [0-9]*[.] *[0-9]+$ ";
String strvalidintegerpattern= "^" ([-]|[ 0-9]) [0-9]*$];
Regex objnumberpattern =new Regex ("+ Strvalidrealpattern +") | ("+ strvalidintegerpattern +"));

Return!objnotnumberpattern.ismatch (Strnumber) &&
!objtwodotpattern.ismatch (Strnumber) &&
!objtwominuspattern.ismatch (Strnumber) &&
Objnumberpattern.ismatch (Strnumber);
}

Function to test for alphabets.

public bool Isalpha (String Strtocheck)
{
Regex objalphapattern=new Regex ("[^a-za-z]");

Return!objalphapattern.ismatch (Strtocheck);
}

Function to Check for alphanumeric.

public bool Isalphanumeric (String Strtocheck)
{
Regex objalphanumericpattern=new Regex ("[^a-za-z0-9]");

Return!objalphanumericpattern.ismatch (Strtocheck);
}


}