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Exception Constructor (String)

Initializes a new instance of the Exception class with a specified error message.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Sub New ( _
	message As String _
)

Parameters

message
Type: System.String
The message that describes the error.

This constructor initializes the Message property of the new instance using the message parameter.

The following table shows the initial property values for an instance of Exception.

Property

Value

InnerException

A null reference (Nothing in Visual Basic).

Message

The error message string.

The following code example derives an Exception for a specific condition. The code demonstrates the use of the constructor that takes a caller-specified message as a parameter, for both the derived class and the base Exception class.


' Example for the Exception( String ) constructor( String ).
Imports System
Imports Microsoft.VisualBasic

Namespace NDP_UE_VB

    ' Derive an exception with a specifiable message.
    Class NotEvenException
        Inherits Exception

        Private Const notEvenMessage As String = _
            "The argument to a function requiring " & _
            "even input is not divisible by 2."

        Public Sub New()
            MyBase.New(notEvenMessage)
        End Sub ' New

        Public Sub New(auxMessage As String)
            MyBase.New(String.Format("{0} - {1}", _
                auxMessage, notEvenMessage))
        End Sub ' New
    End Class ' NotEvenException

    Module NewSExceptionDemo

        Sub Main()
            Console.WriteLine( _
                "This example of the Exception( String )" & vbCrLf & _
                "constructor generates the following output." )
            Console.WriteLine( vbCrLf & _
                "Here, an exception is thrown using the " & vbCrLf & _
                "constructor of the base class." & vbCrLf )

            CalcHalf(18)
            CalcHalf(21)

            Console.WriteLine(vbCrLf & _
                "Here, an exception is thrown using the " & vbCrLf & _
                "constructor of a derived class." & vbCrLf )

            CalcHalf2(30)
            CalcHalf2(33)
        End Sub ' Main

        ' Half throws a base exception if the input is not even.
        Function Half(input As Integer) As Integer

            If input Mod 2 <> 0 Then
                Throw New Exception( String.Format( _
                    "The argument {0} is not divisible by 2.", _
                    input ) )
            Else
                Return input / 2
            End If
        End Function ' Half

        ' Half2 throws a derived exception if the input is not even.
        Function Half2(input As Integer) As Integer

            If input Mod 2 <> 0 Then
                Throw New NotEvenException( _
                    String.Format( "Invalid argument: {0}", input ) )
            Else
                Return input / 2
            End If
        End Function ' Half2

        ' CalcHalf calls Half and catches any thrown exceptions.
        Sub CalcHalf(input As Integer)

            Try
                Dim halfInput As Integer = Half(input)
                Console.WriteLine( _
                    "Half of {0} is {1}.", input, halfInput )

            Catch ex As Exception
                Console.WriteLine( ex.ToString( ) )
            End Try
        End Sub ' CalcHalf


        ' CalcHalf2 calls Half2 and catches any thrown exceptions.
        Sub CalcHalf2( input As Integer )

            Try
                Dim halfInput As Integer = Half2( input )
                Console.WriteLine( _
                    "Half of {0} is {1}.", input, halfInput )

            Catch ex As Exception
                Console.WriteLine( ex.ToString( ) )
            End Try
        End Sub ' CalcHalf2

    End Module ' NewSExceptionDemo
End Namespace ' NDP_UE_VB

' This example of the Exception( String )
' constructor generates the following output.
' 
' Here, an exception is thrown using the
' constructor of the base class.
' 
' Half of 18 is 9.
' System.Exception: The argument 21 is not divisible by 2.
'    at NDP_UE_VB.NewSExceptionDemo.Half(Int32 input)
'    at NDP_UE_VB.NewSExceptionDemo.CalcHalf(Int32 input)
' 
' Here, an exception is thrown using the
' constructor of a derived class.
' 
' Half of 30 is 15.
' NDP_UE_VB.NotEvenException: Invalid argument: 33 - The argument to a function
'  requiring even input is not divisible by 2.
'    at NDP_UE_VB.NewSExceptionDemo.Half2(Int32 input)
'    at NDP_UE_VB.NewSExceptionDemo.CalcHalf2(Int32 input)


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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