Many newcomers to web development cannot get their head around why the carriage returns they made in their data on input from a textarea, or from a text file, Excel spreadsheet etc. do not appear when the web page renders.
The solution is fairly obvious once the newcomer realises that a web page is only the browser's interpretation of html markup, and that a new line in html is represented by the <br /> tag. So what is needed is a way to swap carriage returns or line feeds with the <br /> tag. Well, a way to Replace() them, actually.
<%# Eval("MyMultiLineValue").ToString().Replace(<linebreak>,"<br />") %>
The string.Replace() method allows this, but we also need to identify what we want to replace with the html tag. How is a new line <linebreak> represented in C# or VB.Net?
In C#, it's "\r\n", while in VB.Net, it's vbcrlf. However, there is also a language independent option that does just the same thing: Environment.NewLine.
<%# Eval("MyMultiLineValue").ToString().Replace(Environment.NewLine,"<br />") %>