I used VB.NET Express Edition to test this.
In the resource editor (where you can specify the name of the resource and string content) put the string content separated by Shift+Enter.
Lets say you want to type in
hello
world
Type “hello” followed by Shift+Enter and “world”.
If you look at the Resources.Resx file (which is an xml file), you can see that it creates a node with the attribute xml:space="preserve".
2nd option
Also, you can edit the Resources.resx manually and modify the content to be under CDATA section.
Assume that you have the string named “example”. Search for it in Resources.resx and change the content to have CDATA section inside it as against having a simple value.
e.g.
<data name="example">
<![CDATA[
hello
world
1
2 3
4
]]> </data>