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

Sumit Kumawat

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

5 Replies

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Daril4y ago

The output will be.

You can also use regex to find the special character
+1
Murad BASDAG14y ago
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
}

+2
Vulpes14y ago
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.\?\,\'\;\:\!\-]+$"))
{
MessageBox.Show ("Ok Fine!");
}
else
{
MessageBox.Show("Special Characters are not allowed");
}
+2
Sumit Kumawat14y ago
if (Regex.IsMatch(tbUsername.Text, @"^[a-zA-Z0-9\s.\?\,\'\;\:\!\-]+$"))
{
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
+2
Vulpes14y ago
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
}
+2