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Accepted
J. Rodríguez
Asked: 2020-12-29 12:57:32 +0800 CST 2020-12-29 12:57:32 +0800 CST

What is the difference between ToUpper() and ToUpperInvariant(), in C#

  • 772

Suppose this:

string texto = "Texto a convertir en mayúscula.";

MessageBox.Show("Texto con ToUpper: " + texto.ToUpper() +
                "\nTexto con ToUpperInvariant: " + texto.ToUpperInvariant(),
                "Mensaje en Mayúscula", MessageBoxButtons.OK, MessageBoxIcon.Information);

The result is the same:

  • with ToUpper(): "TEXT TO BE CONVERTED TO UPPERCASE."

  • with ToUpperInvariant(): "TEXT TO BE CONVERTED TO UPPERCASE."

Edited:

According to the description of the ToUpperInvariant: Applies the culture case rules of all languages.

What is the difference, any EXAMPLE where the results may be different?

c#

2 Answers

  1. Best Answer
    • ToUpper(): Take into account the rules of your system's default culture to determine how to convert a string to uppercase.
    • ToUpperInvariant(): Uses what might be called culture neutral to determine the rules for converting a string to uppercase.

    In practice, for the vast majority of letters that we commonly use in English or Spanish, there is really no difference between the 2 methods.

    But in theory, if we were working on a system with a very peculiar culture and with more special characters, then you could notice differences.

    For example, adapting the example from this SO answer , we can see that if we were working on a site where the default culture is Turkish, then we would see a difference in how the iuppercase a is converted:

     string letra = "i";
 var turkeyCulture = new CultureInfo("tr-TR");
 Console.WriteLine(string.Format("{0} ({1})", letra.ToUpperInvariant(), (int)letra.ToUpperInvariant()[0]));
 Console.WriteLine(string.Format("{0} ({1})", letra.ToUpper(turkeyCulture), (int)letra.ToUpper(turkeyCulture)[0]));

    Demo

    Result:

    I (73)
İ (304)

    So it is usually preferable to use ToUpperInvariant()to guarantee stable results, unless we have a special need to take into account the rules of a certain culture.

    • 3

  2. I leave you a link explaining the difference, the only thing is that StackOverFlow is in English, but if you translate it you will understand what it is about:

    https://stackoverflow.com/questions/3550213/in-c-sharp-what-is-the-difference-between-toupper-and-toupperinvariant

    Hope this can help you.

    Cheers

    • 1