How to concatenate two string in Dart?

There are 3 ways to concatenate strings

String a="a";
String b = 'b';

var c1 = a + b; // + operator
var c2 = '$a$b'; // string interpolation
var c3 = 'a' 'b'; // string literals separated only by whitespace are concatenated automatically
var c4 = 'abcdefgh abcdefgh abcdefgh abcdefgh' 
         'abcdefgh abcdefgh abcdefgh abcdefgh';

Usually string interpolation is preferred over the + operator.

There is also StringBuffer for more complex and performant string building.