&= Operator (Visual Basic)
Concatenates a String expression to a String variable or property and assigns the result to the variable or property.
The element on the left side of the &= operator can be a simple scalar variable, a property, or an element of an array. The variable or property cannot be ReadOnly (Visual Basic). The &= operator concatenates the String expression on its right to the String variable or property on its left, and assigns the result to the variable or property on its left.
The & Operator (Visual Basic) can be overloaded, which means that a class or structure can redefine its behavior when an operand has the type of that class or structure. Overloading the & operator affects the behavior of the &= operator. If your code uses &= on a class or structure that overloads &, be sure you understand its redefined behavior. For more information, see Operator Procedures (Visual Basic).