How to check first letter of string is special character or not?

Question

hi all, i want to validate that user name does not contain special character in first letter of string. how to validate this plz help

Murad BASDAG · Answer

If you ask to me ... if (!Char.IsLetter(userName[0])) { // invalid user name } is a very good and effective way to check is the name starts with a letter. But if you additionaly clear spaces in front of the name can be better. For example if (!Char.IsLetter(userName.TrimStart()[0])) { // invalid user name }

Vulpes · Answer

Are you sure that you don't want the first character of the string to contain a letter or digit? If (as I suspect you meant to say) you want the first letter to be a letter or digit but subsequent letters to be any of the characters you've listed in your regular expression, then you could do it like this: if (Regex.IsMatch(tbUsername.Text, @"^ [a-zA-z0-9] [a-zA-Z0-9\s.\?\,\'\;\:\!\-]+$")) { MessageBox.Show ("Ok Fine!"); } else { MessageBox.Show("Special Characters are not allowed"); }

Sumit Kumawat · Answer

if (Regex.IsMatch(tbUsername.Text, @"^[a-zA-Z0-9\s.\?\,\'\;\:\!\-]+$")) { MessageBox.Show ("Ok Fine!"); } else { MessageBox.Show("Special Characters are not allowed"); } this is my code here i want to chk that my input string in tbUsername shuld not contain @"^[a-zA-Z0-9\s.\?\,\'\;\:\!\-]+$" at first place

Vulpes · Answer

It depends what you mean by a special character but the Char structure has a lot of methods which you can use to determine whether a particular character belongs to a specific category or not: http://msdn.microsoft.com/en-us/library/system.char.aspx If, for example, the first character of the user name needed to be a lower or upper case letter you could test with: if (!Char.IsLetter(userName[0])) { // invalid user name }