Question

I’m trying to figure out how to display the repeated letter in a string. For example if the entered string was “red house” it would show that the letter “e” was repeated, then it would be displayed in the label I created. This is a basic program, Here is what I’ve written thus far. Any help is appreciated.

private void button1_Click(object sender, EventArgs e)
    {
        string enteredWord = textBox1.Text;
        char letter;


        for (int index = 0; index < enteredWord.Length; index++) 
        {
            letter = enteredWord[index];

            if (letter == enteredWord[index])
            {
                label1.Text = (letter.ToString());
            }
            else
            { return; 

            }

Answer 1

Could build a HashSet and check each letter. I’m sure there’s a more efficient way, but this should work: (untested)

string enteredWord = textBox1.Text;
HashSet<char> letters = new HashSet<char>();
foreach(char c in enteredWord)
{
    if (letters.Contains(c))
        label1.Text += c.ToString();
    else
        letters.Add(c);
}

EDIT: I suppose this will print out duplicates of the letters if they appear 3 or more times, but you get the idea.