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Is operator (Visual Basic)

  • Чланак

Compares two object reference variables.

Syntax

VB 
result = object1 Is object2

Parts

result
Required. Any Boolean value.

object1
Required. Any Object name.

object2
Required. Any Object name.

Remarks

The Is operator determines if two object references refer to the same object. However, it does not perform value comparisons. If object1 and object2 both refer to the exact same object instance, result is True; if they do not, result is False.

Напомена

The Is keyword is also used in the Select...Case Statement.

Example

The following example uses the Is operator to compare pairs of object references. The results are assigned to a Boolean value representing whether the two objects are identical.

VB 
Dim myObject As New Object
Dim otherObject As New Object
Dim yourObject, thisObject, thatObject As Object
Dim myCheck As Boolean
yourObject = myObject
thisObject = myObject
thatObject = otherObject
' The following statement sets myCheck to True.
myCheck = yourObject Is thisObject
' The following statement sets myCheck to False.
myCheck = thatObject Is thisObject
' The following statement sets myCheck to False.
myCheck = myObject Is thatObject
thatObject = myObject
' The following statement sets myCheck to True.
myCheck = thisObject Is thatObject

As the preceding example demonstrates, you can use the Is operator to test both early bound and late bound objects.

Use TypeOf operator with Is operator

Is operator can also be used with the TypeOf keyword to make a TypeOf...Is expression, which tests whether an object variable is compatible with a data type. For example:

VB 
If TypeOf sender Is Button Then

See also