Monday, 7 March 2016
Text given by user as input is validated before saving it in database tables on client side using Regular Expressions.
Regular Expressions are the patterns which are used to validate the text based on some conditions.
Regex is a class under System.Text.RegularExpressions namespace which is used to validate text based on the given pattern using IsMatch method.
IsMatch method will take string as input to validate with pattern and return true if the text is matched with the pattern or returns false if the text is not matched with the pattern.
Writing patterns
^ - start
$ - end
[a-z] – lower case letters are allowed
[A-Z] – Upper case letters are allowed
[0-9] – Numbers are allowed
[a-zA-Z] – both lower and upper case letters are allowed
[a-zA-Z0-9] – input can be lower case/upper case or numbers
{10} – only 10 characters is valid
{6,10} – 6 to 10 characters are valid
Examples:
Regular Expressions are the patterns which are used to validate the text based on some conditions.
Regex is a class under System.Text.RegularExpressions namespace which is used to validate text based on the given pattern using IsMatch method.
IsMatch method will take string as input to validate with pattern and return true if the text is matched with the pattern or returns false if the text is not matched with the pattern.
Writing patterns
^ - start
$ - end
[a-z] – lower case letters are allowed
[A-Z] – Upper case letters are allowed
[0-9] – Numbers are allowed
[a-zA-Z] – both lower and upper case letters are allowed
[a-zA-Z0-9] – input can be lower case/upper case or numbers
{10} – only 10 characters is valid
{6,10} – 6 to 10 characters are valid
Examples:
10 digit phone number - ^[0-9]{10}$
6 to 15 characters are valid which may
contain lower/upper letters -
^[a-zA-Z]{6,15}$
^[a-zA-Z]{6,15}$
Example to display popup with error message if text is
not a valid
//Validate text with given pattern and return true for
valid and false for invalid text
public bool TextValidate(string Text, string Pattern)
{
//Create regular expression object
with specific pattern
var regex = new Regex(Pattern);
//Check if text matched with
pattern
if (regex.IsMatch(Text))
{
return true;
}//if text not matched with pattern
else { return false; }
}
private void BtnRegister_Click(object
sender, EventArgs e)
{
//intialize errormsg as empty
string errormsg = string.Empty;
//Username - 6 to 15
chars(Upper/Lower) Ex: SudhirChekuri
if (!TextValidate(TxtUsername.Text, "^[a-zA-Z]{6,15}$"))
{
errormsg = "Invalid
Username\nShould be between 6 to 15 letters";
}
//Password and cnfrm pwd match
else if(TxtPassword.Text!=TxtCnfmPwd.Text)
{
errormsg = "Password
and Confirm Password Mismatch";
}//Email Id - ex: sudhir@gmail.com
else if
(!TextValidate(TxtEmailId.Text, @"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"))
{
errormsg = "Invalid
Email Id";
}
//phone number - 10 digits
Ex:9985333333
else if
(!TextValidate(TxtPhoneNo.Text, "^[0-9]{10}$"))
{
errormsg = "Invalid
Phone Number\nEnter 10 digit number";
}
if (errormsg != string.Empty)
{
MessageBox.Show(errormsg);
}
}
