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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)

public Exception(
	string message
)

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. 
using System;

namespace NDP_UE_CS
{
    // Derive an exception with a specifiable message. 
    class NotEvenException : Exception
    {
        const string notEvenMessage = 
            "The argument to a function requiring " +
            "even input is not divisible by 2.";

        public NotEvenException( ) :
            base( notEvenMessage )
        { }

        public NotEvenException( string auxMessage ) :
            base( String.Format( "{0} - {1}", 
                auxMessage, notEvenMessage ) )
        { }
    }

    class NewSExceptionDemo 
    {
        public static void Main() 
        {
            Console.WriteLine( 
                "This example of the Exception( string )\n" +
                "constructor generates the following output." );
            Console.WriteLine( 
                "\nHere, an exception is thrown using the \n" +
                "constructor of the base class.\n" );

            CalcHalf( 18 );
            CalcHalf( 21 );

            Console.WriteLine( 
                "\nHere, an exception is thrown using the \n" +
                "constructor of a derived class.\n" );

            CalcHalf2( 30 );
            CalcHalf2( 33 );
        }
    	
        // Half throws a base exception if the input is not even. 
        static int Half( int input )
        {
            if( input % 2 != 0 )
                throw new Exception( String.Format( 
                    "The argument {0} is not divisible by 2.", 
                    input ) );

            else return input / 2;
        }

        // Half2 throws a derived exception if the input is not even. 
        static int Half2( int input )
        {
            if( input % 2 != 0 )
                throw new NotEvenException( 
                    String.Format( "Invalid argument: {0}", input ) );

            else return input / 2;
        }

        // CalcHalf calls Half and catches any thrown exceptions. 
        static void CalcHalf(int input )
        {
            try
            {
                int halfInput = Half( input );
                Console.WriteLine( 
                    "Half of {0} is {1}.", input, halfInput );
            }
            catch( Exception ex )
            {
                Console.WriteLine( ex.ToString( ) );
            }
        }

        // CalcHalf2 calls Half2 and catches any thrown exceptions. 
        static void CalcHalf2(int input )
        {
            try
            {
                int halfInput = Half2( input );
                Console.WriteLine( 
                    "Half of {0} is {1}.", input, halfInput );
            }
            catch( Exception ex )
            {
                Console.WriteLine( ex.ToString( ) );
            }
        }
    }
}

/*
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_CS.NewSExceptionDemo.Half(Int32 input)
   at NDP_UE_CS.NewSExceptionDemo.CalcHalf(Int32 input)

Here, an exception is thrown using the
constructor of a derived class.

Half of 30 is 15.
NDP_UE_CS.NotEvenException: Invalid argument: 33 - The argument to a function r
equiring even input is not divisible by 2.
   at NDP_UE_CS.NewSExceptionDemo.Half2(Int32 input)
   at NDP_UE_CS.NewSExceptionDemo.CalcHalf2(Int32 input)
*/

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, 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, Zune

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: 3.0, 2.0, 1.0

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