Exception Constructor ()
.NET Framework (current version)
Initializes a new instance of the Exception class.
Assembly: mscorlib (in mscorlib.dll)
This constructor initializes the Message property of the new instance to a system-supplied message that describes the error and takes into account the current system culture.
All the derived classes should provide this default constructor. The following table shows the initial property values for an instance of Exception.
Property | Value |
|---|---|
A null reference (Nothing in Visual Basic). | |
A system-supplied localized description. |
The following code example derives an Exception that uses a predefined message. The code demonstrates the use of the parameterless constructor for the derived class and the base Exception class.
' Example for the Exception( ) constructor. Imports System Imports Microsoft.VisualBasic Namespace NDP_UE_VB ' Derive an exception with a predefined message. Class NotEvenException Inherits Exception Public Sub New( ) MyBase.New( _ "The argument to a function requiring " & _ "even input is not divisible by 2." ) End Sub ' New End Class ' NotEvenException Module NewExceptionDemo Sub Main( ) Console.WriteLine( _ "This example of the Exception( ) constructor " & _ "generates the following output." ) Console.WriteLine( vbCrLf & _ "Here, an exception is thrown using the " & vbCrLf & _ "parameterless constructor of the base class." & _ vbCrLf ) CalcHalf( 12 ) CalcHalf( 15 ) Console.WriteLine(vbCrLf & _ "Here, an exception is thrown using the " & vbCrLf & _ "parameterless constructor of a derived class." & _ vbCrLf ) CalcHalf2( 24 ) CalcHalf2( 27 ) 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( ) 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( ) 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 ' NewExceptionDemo End Namespace ' NDP_UE_VB ' This example of the Exception( ) constructor generates the following output. ' ' Here, an exception is thrown using the ' parameterless constructor of the base class. ' ' Half of 12 is 6. ' System.Exception: Exception of type System.Exception was thrown. ' at NDP_UE_VB.NewExceptionDemo.Half(Int32 input) ' at NDP_UE_VB.NewExceptionDemo.CalcHalf(Int32 input) ' ' Here, an exception is thrown using the ' parameterless constructor of a derived class. ' ' Half of 24 is 12. ' NDP_UE_VB.NotEvenException: The argument to a function requiring even input i ' s not divisible by 2. ' at NDP_UE_VB.NewExceptionDemo.Half2(Int32 input) ' at NDP_UE_VB.NewExceptionDemo.CalcHalf2(Int32 input)
Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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