Go4Expert - Reusable validation methods in C# .Net

Introduction

Many times we need to check or validations for numeric/string/Alphanumeric values.
Background

It provides some methods in C# .Net, which can be resue in your web or windows application.
The code

Code:
using System;

using System.Text.RegularExpressions;

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 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 + ")|(" + trValidIntegerPattern + ")");

    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);

  }

}