Extension Methods in . NET does not work

Question

I’m trying to create a Extension Methods for the class string. He’s not showing up.

My class with the extension method:

namespace MEUPROJETO.Extension
{
    public static class StringExtension
    {
        public static string PrimeiraLetraDeCadaPalavraMiuscula(this string frase)
        {
            frase = frase.ToLower();

            System.Globalization.CultureInfo cultureinfo = System.Threading.Thread.CurrentThread.CurrentCulture;

            return cultureinfo.TextInfo.ToTitleCase(frase);

        }
    }
}

Class where I try to use it:

namespace MEUPROJETO.Teste
{
   public static class TesteExt
   {
       public static void teste( )
       {
         string catdescription = "TESTANDO a frase nessa STRING.";

         catdescription = catdescription.PrimeiraLetraDeCadaPalavraMiuscula();
       }
   }
}

He can’t even compile, says the method doesn’t exist, like I do for him to appear?

The namespace influences?

Answer 1

I am putting the answer that the ramaral put in the comments, when he create his answer here I mark his as correct answer.

The solution is to add the namespace using MEUPROJETO.Extension where I want to use the methods.

Answer 2

You didn’t mark the method PrimeiraLetraDeCadaPalavraMiuscula as an extension, add the following attribute to the variable declaration:

    [Runtime.CompilerServices.Extension()]
    public static String PrimeiraLetraDeCadaPalavraMiuscula(this string frase) //não precisa do this
    {
        frase = frase.ToLower();
        Globalization.CultureInfo cultureinfo = Threading.Thread.CurrentThread.CurrentCulture;

        return cultureinfo.TextInfo.ToTitleCase(frase).ToString;

    }