Hangman game: error if the quessword contains a letter more than once

Question

This is for a hangman program it works fine if the word I am guessing only contains each letter once but if it contains one or more of the letters twice when I click on the letter again nothing happens.

private void charGuess(char letter ) 
{
    if (!myWords[randomNum].guess_word.Contains(letter))
    {
        totalWrongGuesses(letter);
    }
    else
    {
        int tempIndex = myWords[randomNum].guess_word.IndexOf(letter);
        astericksBox.Text = astericksBox.Text
            .Remove(tempIndex,1)
            .Insert(tempIndex,letter
            .ToString());
    }

    if (!astericksBox.Text.Contains("*"))
    {
        MessageBox.Show("You've Won!!");  
    }
}

private int randomNumGenerator()
{
    int rndNum; // a variable to temporarily store the random number generated
    Random randomNum = new Random(); // creates a new Random object randomNum
    return rndNum = randomNum.Next(0,19); // returns a randomNum vlue between 0 and 19
}


private void button15_Click(object sender, EventArgs e)
{
    charGuess('a');
}

Update: I found the solution for my problem and posted it as an answer below.

Answer 1

replace the body of your else with

var indexes = AllIndexesOf(myWords[randomNum].guess_word,letter);
foreach(int i in indexes)
    astericksBox.Text = astericksBox.Text.Remove(i,1).Insert(i,letter.ToString());

and create this function (which i got from Finding ALL positions of a substring in a large string in C# )

public static List<int> AllIndexesOf(this string str, string value)

    if (String.IsNullOrEmpty(value))
        throw new ArgumentException("the string to find may not be empty", "value");
    List<int> indexes = new List<int>();
    for (int index = 0; ; index += value.Length)
    {
        index = str.IndexOf(value, index);
        if (index == -1)
            return indexes;
        indexes.Add(index);
    }
}

Answer 2

Replace this:

int tempIndex = myWords[randomNum].guess_word.IndexOf(letter);
astericksBox.Text = astericksBox.Text.Remove(tempIndex,1).Insert(tempIndex,letter.ToString());

With this:

int tempIndex = 0;
do 
{
    tempIndex = myWords[randomNum].guess_word.IndexOf(letter, tempIndex);
    astericksBox.Text = astericksBox.Text.Remove(tempIndex,1).Insert(tempIndex,letter.ToString());
    tempIndex++;
}
while (tempIndex > 0);

And for efficiency/performance I might do this:

int tempIndex = 0;
var mask = astericksBox.Text.ToCharArray();
do 
{
    tempIndex = myWords[randomNum].guess_word.IndexOf(letter, tempIndex);
    mask[tempIndex] = letter;          
    tempIndex++;
}
while (tempIndex > 0);
astericksBox.Text = new string(mask);

That code also reads a lot easier.

Answer 3

I changed the else statement in charGuess to the code below and it now works as expected.

else
            {
                int tempIndex = myWords[randomNum].guess_word.IndexOf(letter);
                String tempWord = myWords[randomNum].guess_word;
                astericksBox.Text = astericksBox.Text.Remove(tempIndex,1).Insert(tempIndex,letter.ToString());
                tempWord = tempWord.Remove(tempIndex, 1).Insert(tempIndex, "£");
                myWords[randomNum].guess_word = tempWord;

            }