using System;
using System.IO;
 
public class Test
{
	public static void Main()
	{
	  string texto = 
    @"Isto é um exemplo. E quero que na label1 apareceça o que está dentro de aspas.
      Ou seja, o texto que se encontra ""aqui.txt"". 
      Porém a label1 não sabe o que estará na textbox.";
 
      int valorPos = texto.IndexOf(@"""") + 1;
      string valorEntreAspas = texto.Substring(valorPos, texto.IndexOf(@"""", valorPos) - valorPos);
      string arquivoSemExtensao = Path.GetFileNameWithoutExtension(valorEntreAspas);
 
      Console.WriteLine(arquivoSemExtensao); // aqui.txt
      Console.ReadLine();
	}
}

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