Turn the first letter of a string into uppercase?

Question

Example:

I have a string "stack exchange", how do I transform your first character, getting "Stack exchange"?

Answer 1

That’s it:

var texto = "stack exchange";
var upper = char.ToUpper(texto[0]) + texto.Substring(1);

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

• Char.ToUpper()
• Substring()

There are better ways to resolve the issue but that are outside the requirement of the question. If interested already have a question on the subject here.

This form is more readable to most programmers than using LINQ. It’s obvious to anyone what the algorithm does. No need to add a namespace extra to run it. Readability is subjective but size is not and this is shorter. It uses less methods. Of course it can be argued that it also uses 2 operators and that deep down they are methods, but C# is not Java. If operators are methods, it’s implementation detail and you can’t argue about expressiveness by ignoring it. I find it more expressive to use operators than methods. You have to think otherwise, so this is subjective. Each one chooses what is best for themselves.

Besides, this one’s actually faster. I always defend in my answers that one should not do premature optimization, that one should not pursue useless performance gains. But it’s not always obvious what’s useful or not. If you go through this algorithm in a method that has the potential to be used within long loops, the gain becomes important. Otherwise, BCL’s methods would not need to be as optimized as they are. Nor am I preaching optimization by optimization, but if there is a simple way to do it like this, if it has no real disadvantage (being idiomatic is questionable, because nobody said that programming in a declarative or functional way is the right one in C#, it is only an option, besides being idiomatic has to bring clear advantages, when this does not happen, it is silly to pursue ideals, it would be premature). In some scenarios the difference is anything but contemptible.

Answer 2

Tip from ONLY in English, small method to do this:

public static string FirstCharToUpper(string input)
{
    if (String.IsNullOrEmpty(input))
        throw new ArgumentException("Insira uma palavra diferente de nula ou vazia");
    return input.First().ToString().ToUpper() + input.Substring(1);
}

You might also be interested in another transformation, to Title Case (also known as Capitalize). It turns "stack exchange" to "STack AndXchange":

public string ToTitleCase(string str)
{
    return CultureInfo.CurrentCulture.TextInfo.ToTitleCase(str.ToLower());
}

Answer 3

You can enter the features of the previous answers in a Static class and access it from anywhere.

Implementation:

public static class StringExtends
{
   public static string FirstCharToUpper(this string input)
   {
      if (String.IsNullOrEmpty(input))
         throw new ArgumentException("Insira uma palavra diferente de nula ou vazia");
      return input.Length > 1 ? char.ToUpper(input[0]) + input.Substring(1) : input.ToUpper();
   }
}

Utilizing:

var texto = "stack exchange";
var upper = texto.FirstCharToUpper();

example|. Net Fiddle