Get first three letters from every string in C#

The following are our strings in a list −

List<object> list = new List<object> { "keyboard", "mouse", "joystick", "monitor" };

To use the first 3 letters, use substring method and use it under the Linq Select method.

IEnumerable<string> res = list.AsQueryable() .Cast<string>() .Select(str => str.Substring(0, 3));

Example

 Live Demo

using System;
using System.Linq;
using System.Collections.Generic;
class Demo {
   static void Main() {
      List<object> list = new List<object> { "keyboard", "mouse", "joystick", "monitor" };
      // getting first 3 letters from every string
      IEnumerable<string> res = list.AsQueryable() .Cast<string>() .Select(str =>       str.Substring(0,3));
      foreach (string str in res) {
         Console.WriteLine(str);
      }
   }
}

Output

key
mou
joy
mon