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.NET Framework Class Library
Exception..::.InnerException Property

Updated: November 2007

Gets the Exception instance that caused the current exception.

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

Visual Basic (Declaration)
Public ReadOnly Property InnerException As Exception
Visual Basic (Usage)
Dim instance As Exception
Dim value As Exception

value = instance.InnerException
C#
public Exception InnerException { get; }
Visual C++
public:
virtual property Exception^ InnerException {
    Exception^ get () sealed;
}
J#
/** @property */
public final Exception get_InnerException()
JScript
public final function get InnerException () : Exception

Property Value

Type: System..::.Exception

An instance of Exception that describes the error that caused the current exception. The InnerException property returns the same value as was passed into the constructor, or a null reference (Nothing in Visual Basic) if the inner exception value was not supplied to the constructor. This property is read-only.

Implements

_Exception..::.InnerException

When an exception X is thrown as a direct result of a previous exception Y, the InnerException property of X should contain a reference to Y.

Use the InnerException property to obtain the set of exceptions that led to the current exception.

You can create a new exception that catches an earlier exception. The code that handles the second exception can make use of the additional information from the earlier exception to handle the error more appropriately.

Suppose that there is a function that reads a file and formats the data from that file. In this example, as the code tries to read the file, an IOException is thrown. The function catches the IOException and throws a FileNotFoundException. The IOException could be saved in the InnerException property of the FileNotFoundException, enabling the code that catches the FileNotFoundException to examine what causes the initial error.

The InnerException property, which holds a reference to the inner exception, is set upon initialization of the exception object.

The following example demonstrates throwing and catching an exception that references an inner exception.

Visual Basic
Imports System

Public Class MyAppException
   Inherits ApplicationException

   Public Sub New(message As [String])
      MyBase.New(message)
   End Sub 'New

   Public Sub New(message As [String], inner As Exception)
      MyBase.New(message, inner)
   End Sub 'New
End Class 'MyAppException

Public Class ExceptExample

   Public Sub ThrowInner()
      Throw New MyAppException("ExceptExample inner exception")
   End Sub 'ThrowInner

   Public Sub CatchInner()
      Try
         Me.ThrowInner()
      Catch e As Exception
         Throw New MyAppException("Error caused by trying ThrowInner.", e)
      End Try
   End Sub 'CatchInner
End Class 'ExceptExample

Public Class Test

   Public Shared Sub Main()
      Dim testInstance As New ExceptExample()
      Try
         testInstance.CatchInner()
      Catch e As Exception
         Console.WriteLine("In Main catch block. Caught: {0}", e.Message)
         Console.WriteLine("Inner Exception is {0}", e.InnerException)
      End Try
   End Sub 'Main
End Class 'Test
C#
using System;
public class MyAppException:ApplicationException 
{
   public MyAppException (String message) : base (message) 
   {}
   public MyAppException (String message, Exception inner) : base(message,inner) {}    
   }
public class ExceptExample 
{
   public void ThrowInner () 
   {
   throw new MyAppException("ExceptExample inner exception");
   }
   public void CatchInner() 
   {
      try 
      {
      this.ThrowInner();
      }
         catch (Exception e) 
         {
         throw new MyAppException("Error caused by trying ThrowInner.",e);
         }
      }
   }
public class Test 
{
   public static void Main() 
   {
   ExceptExample testInstance = new ExceptExample();
      try 
      {
      testInstance.CatchInner();
      }
         catch(Exception e) 
         {
         Console.WriteLine ("In Main catch block. Caught: {0}", e.Message);
         Console.WriteLine ("Inner Exception is {0}",e.InnerException);
         }
      }
}
Visual C++
using namespace System;
public ref class MyAppException: public ApplicationException
{
public:
   MyAppException( String^ message )
      : ApplicationException( message )
   {}

   MyAppException( String^ message, Exception^ inner )
      : ApplicationException( message, inner )
   {}

};

public ref class ExceptExample
{
public:
   void ThrowInner()
   {
      throw gcnew MyAppException( "ExceptExample inner exception" );
   }

   void CatchInner()
   {
      try
      {
         this->ThrowInner();
      }
      catch ( Exception^ e ) 
      {
         throw gcnew MyAppException( "Error caused by trying ThrowInner.",e );
      }

   }

};

int main()
{
   ExceptExample^ testInstance = gcnew ExceptExample;
   try
   {
      testInstance->CatchInner();
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "In Main catch block. Caught: {0}", e->Message );
      Console::WriteLine( "Inner Exception is {0}", e->InnerException );
   }

}
J#
import System.*;
public class MyAppException extends ApplicationException
{
    public MyAppException(String message)
    {
      super(message);
    } //MyAppException

    public MyAppException(String message, System.Exception inner)
    {
      super(message, inner);
    } //MyAppException
} //MyAppException

public class ExceptExample
{
    public void ThrowInner()throws MyAppException
    {
        throw new MyAppException("ExceptExample inner exception");
    } //ThrowInner

    public void CatchInner()throws MyAppException
    {
        try {
            this.ThrowInner();
        }
        catch (System.Exception e) {
            throw new MyAppException("Error caused by trying ThrowInner.", e);
        }
    } //CatchInner
} //ExceptExample

public class Test
{
    public static void main(String[] args)
    {
        ExceptExample testInstance = new ExceptExample();
        try {
            testInstance.CatchInner();
        }
        catch (System.Exception e) {
            Console.WriteLine("In main catch block. Caught: {0}", 
                e.get_Message());
            Console.WriteLine("Inner Exception is {0}", 
                e.get_InnerException());
        }
    } //main
} //Test

This code has the following output: 

In Main
  catch block. Caught: Error caused by trying ThrowInner. Inner Exception is
  MyAppException: ExceptExample inner exception at ExceptExample.ThrowInner() at
  ExceptExample.CatchInner()

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 2.0, 1.0
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