InvalidCastExce ption from explicit casting object to a class

[Kevin]

Hi

I try the following program and I get InvalidCastExce ption at the line

MyByte b = (MyByte)obj;

If I change it to

MyByte b = (MyByte)d;

it works fine.

I need to convert the obj to MyByte type. Do you know a way to do it?

Thanks in advance.

using System;

namespace ConsoleApplicat ion1
{
/// <summary>
/// Summary description for Class1.
/// </summary>
struct Digit
{
byte value;

public Digit(byte value)
{
if (value > 9) throw new ArgumentExcepti on();
this.value = value;
}

public byte ByteValue
{
get
{
return ( this.value );
}
set
{
this.value = value;
}
}
// define implicit Digit-to-byte conversion operator:
public static implicit operator byte(Digit d)
{
Console.WriteLi ne("conversion occurred");
return d.value;
}
}

struct MyByte
{
byte value;

public MyByte(byte value)
{
if (value > 9) throw new ArgumentExcepti on();
this.value = value;
}

// define implicit Digit-to-byte conversion operator:
public static implicit operator MyByte(Digit d)
{
Console.WriteLi ne("conversion occurred");
return new MyByte(d.ByteVa lue);
}
}

class Class1
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
public static void Main()
{
Digit d = new Digit(3);
object obj = d;

MyByte b = (MyByte)obj;
System.Console. WriteLine(b);
}
}
}

[Jon Skeet [C# MVP]]

Kevin <ke************ **@hotmail.com> wrote:

I try the following program and I get InvalidCastExce ption at the line

MyByte b = (MyByte)obj;

If I change it to

MyByte b = (MyByte)d;

it works fine.

I need to convert the obj to MyByte type. Do you know a way to do it?

When you're unboxing, you need to unbox to the exact value type and
*then* you can do other conversions. So, you should be able to do:

MyByte b = (MyByte)(Digit) obj;

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Marina]

Well, if 'd' refers to an instance of MyByte, and 'obj' doesn't, then that
is why. You can't convert a type that is not compatible with MyByte to
MyByte.

This post makes no sense, as you didn't say what 'obj' is or what 'd' is.

"Kevin" <ke************ **@hotmail.com> wrote in message
news:Of******** *****@TK2MSFTNG P11.phx.gbl...

Hi

I try the following program and I get InvalidCastExce ption at the line

MyByte b = (MyByte)obj;

If I change it to

MyByte b = (MyByte)d;

it works fine.

I need to convert the obj to MyByte type. Do you know a way to do it?

Thanks in advance.

using System;

namespace ConsoleApplicat ion1
{
/// <summary>
/// Summary description for Class1.
/// </summary>
struct Digit
{
byte value;

public Digit(byte value)
{
if (value > 9) throw new ArgumentExcepti on();
this.value = value;
}

public byte ByteValue
{
get
{
return ( this.value );
}
set
{
this.value = value;
}
}
// define implicit Digit-to-byte conversion operator:
public static implicit operator byte(Digit d)
{
Console.WriteLi ne("conversion occurred");
return d.value;
}
}

struct MyByte
{
byte value;

public MyByte(byte value)
{
if (value > 9) throw new ArgumentExcepti on();
this.value = value;
}

// define implicit Digit-to-byte conversion operator:
public static implicit operator MyByte(Digit d)
{
Console.WriteLi ne("conversion occurred");
return new MyByte(d.ByteVa lue);
}
}

class Class1
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
public static void Main()
{
Digit d = new Digit(3);
object obj = d;

MyByte b = (MyByte)obj;
System.Console. WriteLine(b);
}
}
}

[Kevin]

I am sorry that I don't state my problem clearly. I know that "MyByte b =
(MyByte)(Digit) obj;" works. Unfortunately, this call is in an external
library and I cannot change. I want to know if there is any other way to
make the casting from object to MyByte works.

Thanks.

"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com...

Kevin <ke************ **@hotmail.com> wrote:

I try the following program and I get InvalidCastExce ption at the line

MyByte b = (MyByte)obj;

If I change it to

MyByte b = (MyByte)d;

it works fine.

I need to convert the obj to MyByte type. Do you know a way to do it?

When you're unboxing, you need to unbox to the exact value type and
*then* you can do other conversions. So, you should be able to do:

MyByte b = (MyByte)(Digit) obj;

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Kevin <ke************ **@hotmail.com> wrote:

I am sorry that I don't state my problem clearly. I know that "MyByte b =
(MyByte)(Digit) obj;" works. Unfortunately, this call is in an external
library and I cannot change. I want to know if there is any other way to
make the casting from object to MyByte works.

Not if the object in question isn't actually a MyByte, no.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too