Regex to return unique lines when pattern matched

Question

I am parsing a log file and trying to match error statements. The part of the line I am matching "error CS" will apply to numerous lines some duplicates some not. Is there a way I can not return the duplicates. Using Java flavor of RegEx..

example: my simple regex returns

Class1.cs(16,27): error CS0117: 'string' does not contain a definition for 'empty'
Class1.cs(34,20): error CS0103: The name 'thiswworked' does not exist in the current context
Class1.cs(16,27): error CS0117: 'string' does not contain a definition for 'empty'
Class1.cs(34,20): error CS0103: The name 'thiswworked' does not exist in the current context

would like it to return:

Class1.cs(16,27): error CS0117: 'string' does not contain a definition for 'empty'
Class1.cs(34,20): error CS0103: The name 'thiswworked' does not exist in the current context