.net - Resolve strange compiler error -

I have such lines:

  String as myNewStringValue: myNewStringValue = "Hello"  

I am trying to convert them all into several lines, that is, to remove the character, because : However, it results in a strange compiler error:

after that Some can not even, I do conclude it is I, even if I undo all the error persists.

Is there anything that I can stop it?

Based on the question, usually something like clear solution and then Can be solved by rebuilding solution .

It is not always enough for yourself to do reconstruction solutions for just .