Translate a string into a telephone keypad code

TelephoneKeypad.cs

using System.Collections.Generic;
using System.Text;

static string TranslateToNumber(string input)
{
	var map = new Dictionary<char, char>
	{
		{'a', '2'}, {'b', '2'}, {'c', '2'},
		{'d', '3'}, {'e', '3'}, {'f', '3'},
		{'g', '4'}, {'h', '4'}, {'i', '4'},
		{'j', '5'}, {'k', '5'}, {'l', '5'},
		{'m', '6'}, {'n', '6'}, {'o', '6'},
		{'p', '7'}, {'q', '7'}, {'r', '7'}, {'s', '7'},
		{'t', '8'}, {'u', '8'}, {'v', '8'},
		{'w', '9'}, {'x', '9'}, {'y', '9'}, {'z', '9'}
	};

	var result = new StringBuilder();
	foreach (var c in input)
	{
		result.Append(map.TryGetValue(c, out var value) ? value : c);
	}

	return result.ToString();
}