Question: ```
Str.replace(',','','');

```

I have to replace `(,)` with `(',')`

but in replace function we have to pass character in `' '` so it is giving me an error.

Answer: 
[String.Replace](http://msdn.microsoft.com/en-us/library/System.String.Replace%28v=vs.80%29.aspx) has 2 overloads, one accepts `char` and one accepts `string` so you can do this:

```
var value = existing.Replace(",", "','");

```
`','` is clearly more than one character. So you can't use [`String.Replace(Char, Char)`](http://msdn.microsoft.com/en-us/library/czx8s9ts.aspx) overload.

You can use [`String.Replace(String, String)`](http://msdn.microsoft.com/en-us/library/fk49wtc1.aspx) overload instead.

```
string s = ",,";
Console.WriteLine(s.Replace(",", "','"));

```

Output will be;

```
','','

```

Here a [`DEMO`](http://ideone.com/aXpQKW).