Splitting Lines with String Literals
When you type long sting literals, ReSharper helps you split the lines adding the necessary quotation marks and plus signs.
While the caret is within a string literal, 
Now, if you delete the + sign, the string parts will be back together without redundant quotes.
Another way of splitting a string literal is to set the caret where you want to split the string, press Alt+Enter and choose Split string. This context action will also add necessary quotation marks and +, but both parts of the sting will stay on the same line.
This feature is supported in the following languages/technologies:
The instructions and examples given here address the use of the feature in C#. For details specific to other languages, see corresponding topics in the ReSharper by Language section. Specifically: