Question: How can I find all indexes of a pattern in a string using c#? 

For example I want to find all `##` pattern indexes in a string like this `45##78$$#56$$JK01UU`

Answer: 
```
 string pattern = "##";
 string sentence = "45##78$$#56$$J##K01UU";
 IList<int> indeces = new List<int>();
 foreach (Match match in Regex.Matches(sentence, pattern))
 {
      indeces.Add(match.Index);
 }

```

indeces will have 2, 14
You can get all the indices of a pattern in a string by using a regex search like this.

```
string input = "45##78$$#56$$JK01UU", pattern = Regex.Escape("##");
Regex rx = new Regex(pattern);
var indices = new List<int>();
var matches = rx.Matches(s);
for (int i=0 ; i<matches.Length ; i++)
{
    indices.Add(matches[i].Index);
}

```