How to get only first letters from string in C#

Question

I am new to C# and I am using windows forms. I am dealing with Postcodes string and I am trying to get the first letters from the Post code and store it in a variable, for example:

BL9 8NS (I want to get BL)

L8 6HN (I want to get L)

CH43 7TA (I want to get CH)

WA8 7LX (I want to get WA)

I just want to get the first letters before the number and as you can see the number of letters can be 1 or 2 and maybe 3. Anyone knows how to do it? Thank you

Answer 1

Since string imlements IEnumerable<char>, using Linq TakeWhile and char.IsLetter would be very easy:

string firstLetters = string.Concat(str.TakeWhile(char.IsLetter));

Answer 2

Use a regex with a group to match the first letters.

This is the regex you need:

^([a-zA-Z]+)

You can use it like this:

Regex.Match("BL9 8NS", "^([a-zA-Z]+)").Groups[1].Value

The above expression will evaluate to "BL".

Remember to add a using directive to System.Text.RegularExpressions!

Answer 3

You can use StringBuilder and loop through the characters until the first non-letter.

string text = "BL9 8NS";
StringBuilder sb = new StringBuilder();
foreach(char c in text) {
    if(!char.IsLetter(c)) {
        break;
    }
    sb.Append(c);
}
string result = sb.ToString(); // BL

Or if you don't care about performance and just want it simple, you can use TakeWhile:

string result = new string(text.TakeWhile(c => char.IsLetter(c)).ToArray());