I am having below string and filename, the filename is the output of another function, so it look like below

```
string filename = "maindestination.jpg"; //It can .png, .gif etc depend on the type of file.

```

Then I have got another function which gives the output as below

```
string id = "tcm:123-3455";

```

Now I want to write a function something like below which will do the merging of both the outputted values as below:

```
public static string newFileName(string filename, string strID)
{
string newFileName = "maindestination_tcm:123-3455.jpg"
return newFileName;
}

```