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-= Operator (Visual Basic)

Subtracts the value of an expression from the value of a variable or property and assigns the result to the variable or property.

variableorproperty -= expression


Required. Any numeric variable or property.


Required. Any numeric expression.

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 assigns the value on its right 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).

The following example uses the -= operator to subtract one Integer variable from another and assign the result to the latter variable.

Dim var1 As Integer = 10
Dim var2 As Integer = 3
var1 -= var2
' The value of var1 is now 7.