IsError Function

IsError Function

Class

Microsoft.VisualBasic.Information

Syntax

 IsError(   expression   )

expression (required; Object): An object variable that may be an Exception object

Return Value

Boolean ( True if expression is an Exception object, False otherwise )

Description

Indicates whether an object is an instance of the Exception class or one of its derived classes

Example

 Module modMain Public Sub Main Dim oUnk As Object = "This is an object of subtype String." 'Dim oUnk As Object = 10 Dim oResult As Object = Increment(oUnk) If Not IsError(oResult) Then    Console.WriteLine(oResult) Else    Console.WriteLine(oResult.Message) End If End Sub Public Function Increment(o As Object) As Object    If IsNumeric(o) Then       o += 1       Return o    Else       Dim e As New System.InvalidOperationException       Return e     End If End Function End Module

VB.NET/VB 6 Differences

In VB 6, the IsError function takes a variant argument and determines if its subtype is vbError . Most commonly, it is used with the CVErr function to determine if the value returned from a function is an error. In VB.NET, the IsError function is used to test whether an object is an instance of the Exception class or its derived classes.