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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
)
public Exception (
	String message
)
public function Exception (
	message : String
)

Parameters

message

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)
*/

// Example for the Exception( string ) constructor.
package NDP_UE_JSL; 

import System.* ;

// Derive an exception with a specifiable message.
class NotEvenException extends System.Exception
{
    private String notEvenMessage = "The argument to a function requiring " 
        + "even input is not divisible by 2.";

    public NotEvenException()
    {
        super("The argument to a function requiring " 
            + "even input is not divisible by 2.");
    } //NotEvenException

    public NotEvenException(String auxMessage)
    {
        super(String.Format("{0} - " + "The argument to a function requiring " 
            + "even input is not divisible by 2.", auxMessage));
    } //NotEvenException
} //NotEvenException

class NewSExceptionDemo
{
    public static void main(String[] args)
    {
        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);
    } //main

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

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

    // 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}.", 
                System.Convert.ToString(input), 
                System.Convert.ToString(halfInput));
        }
        catch (System.Exception ex) {
            Console.WriteLine(ex.toString());
        }
    } //CalcHalf

    // 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}.", 
                System.Convert.ToString(input), 
                System.Convert.ToString(halfInput));
        }
        catch (System.Exception ex) {
            Console.WriteLine(ex.toString());
        }
    } //CalcHalf2
} //NewSExceptionDemo
   
/*
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_JSL.NewSExceptionDemo.Half(Int32 input) in C:\Documents and Setting
s\jitesh_chourasia\My Documents\Visual Studio Projects\ConsoleApp - JS\ConsoleAp
p - JS\Class1.jsl:line 47
   at NDP_UE_JSL.NewSExceptionDemo.CalcHalf(Int32 input) in C:\Documents and Set
tings\jitesh_chourasia\My Documents\Visual Studio Projects\ConsoleApp - JS\Conso
leApp - JS\Class1.jsl:line 72

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

Half of 30 is 15.
NDP_UE_JSL.NotEvenException: Invalid argument: 33 - The argument to a function r
equiring even input is not divisible by 2.
   at NDP_UE_JSL.NewSExceptionDemo.Half2(Int32 input) in C:\Documents and Settin
gs\My Documents\Visual Studio Projects\ConsoleApp - JS\ConsoleApp - JS\
Class1.jsl:line 60
   at NDP_UE_JSL.NewSExceptionDemo.CalcHalf2(Int32 input) in C:\Documents and Se
ttings\My Documents\Visual Studio Projects\ConsoleApp - JS\Cons
oleApp - JS\Class1.jsl:line 87
*/

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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