>>Use @ prefix.
>
>@ prefix adds line feeds to strings.
>So result string is different and cannot be used in case label.
>
>>PS: In most cases it's easier to use StringBuilder.
>
>I need to use string literal in case label as shown in example.
>case label cannot be expression so using StringBuilder is not possible.

strin s1 = @"IR(""xxx"")+
sql('sele tasudok from dok x
 where doktyyp+str(dokumnr,7)= ""G""+
str(dok.krdokumnr,7) ','')".Replace("\r\n",String.Empty);

//..
case s1: 

Using such a string as a label is dangerous but it is up to you.
Cetin