C # Regular Expression example

The following example shows the use of Regular Expresssions in C #. This program has basic validation scripts for validation easily useable in all programs.

/*
<HowToCompile>
Csc/r: System. Text. RegularExpressions. dll, System. dll Validation. cs
</HowToComplie>
*/

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 cumulative sive

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-]");
Regex objIntPattern = new Regex ("^-[0-9] + $ | ^ [0-9] + $ ");

Return! ObjNotIntPattern. IsMatch (strNumber )&&
ObjIntPattern. IsMatch (strNumber );
}

// Function to Test for Positive Number both Integer & 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 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 );
}

}

There is another simple way to perform these validation think of it while the next article comes.