I have a public variable in a class of type color declared as follows:

public mycolor as color = color.Empty

I want to check to see if the user has specified a color like;

if mycolor = Color.Empty then.....
or
if mycolor is Color.Empty then .......

I get errors saying that = can be used for colors and is can't be used with
value types. I give up...how do I do this. Thanks.
--
Dennis in Houston

Since ValueType derives from Object, you can use the Equals method. For
Value Types, this returns true if the instances are of the same type and
have the same value.

If mycolor.Equals(Color.Empty) Then
MessageBox.Show("mycolor is Empty")
End If

hope that helps..
Imran.


"Dennis" <(E-Mail Removed)> wrote in message
news:9A638870-CBE0-47D8-A453-(E-Mail Removed)...
>I have a public variable in a class of type color declared as follows:
>
> public mycolor as color = color.Empty
>
> I want to check to see if the user has specified a color like;
>
> if mycolor = Color.Empty then.....
> or
> if mycolor is Color.Empty then .......
>
> I get errors saying that = can be used for colors and is can't be used
> with
> value types. I give up...how do I do this. Thanks.
> --
> Dennis in Houston

Dennis,
Did you try the Equals function or the Equals Operator?

If mycolor.Equals(Color.Empty) Then

End If

To use the Equals Operator you need to call the shared function that is
created.

If Color.op_Equality(mycolor, Color.Empty) Then

End If

See the Color.Equals function in the online help for some important remarks
about using Color.Equals and when you may want to use Color.ToArgb to
compare two colors.

If mycolor.ToArgb() = Color.Empty.ToArgb() Then

End If


NOTE: VS.NET 2005 (aka Whidbey, due out later in 2005) will support calling
the Equals Operator with the familiar "=" syntax. For information on VS.NET
2005 see http://lab.msdn.microsoft.com/vs2005/.

' VS.NET 2005 sample
If mycolor = Color.Empty Then

End If

Hope this helps
Jay

"Dennis" <(E-Mail Removed)> wrote in message
news:9A638870-CBE0-47D8-A453-(E-Mail Removed)...
>I have a public variable in a class of type color declared as follows:
>
> public mycolor as color = color.Empty
>
> I want to check to see if the user has specified a color like;
>
> if mycolor = Color.Empty then.....
> or
> if mycolor is Color.Empty then .......
>
> I get errors saying that = can be used for colors and is can't be used
> with
> value types. I give up...how do I do this. Thanks.
> --
> Dennis in Houston

Dennis,

As alternative
If mycolor.ToArgb = mycolor.Empty.ToArgb

End if

Cor

"Dennis" <(E-Mail Removed)>:
>
> public mycolor as color = color.Empty
>
> I want to check to see if the user has specified a color like;
>
> if mycolor = Color.Empty then.....
> or
> if mycolor is Color.Empty then .......
>
> I get errors saying that = can be used for colors and is can't be used
> with
> value types. I give up...how do I do this. Thanks.
> --
> Dennis in Houston

"Cor Ligthert" <(E-Mail Removed)> schrieb:
> As alternative
> If mycolor.ToArgb = mycolor.Empty.ToArgb

This only works for 'Color'. I would stick with the more general pattern of
using 'Equals'...

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>

"Herfried K. Wagner [MVP]"

>>As alternative
>>If mycolor.ToArgb = mycolor.Empty.ToArgb

> This only works for 'Color'. I would stick with the more general pattern
> of using 'Equals'...

You are free to do that. I will not blaim you for that.

However I use this one, I find it nicer just a personal choise

May I do that as well?

:-)

Cor

Cor (& Herfried),
As I stated in my initial reply:

> See the Color.Equals function in the online help for some important
> remarks about using Color.Equals and when you may want to use Color.ToArgb
> to compare two colors.

If I want to compare what is visible seen I will use Color.ToArgb in other
words to compare the Alpha, Red, Green & Blue values.

If I want to compare what is literally used I will use Color.Equals or
Color.op_Equality, in other words to compare the names of the color or the
values for unnamed colors.

For example:

Dim color1 As Color = Color.Black
Dim color2 As Color = Color.FromArgb(0,0,0)

Both are visibly Black, however they are not logically the same value. In
other words:

If color1.Equals(color2) Then
' color1 is the same named color as color2
End If

If color1.ToArgb() = color2.ToArgb() Then
' color1 & color2 have the same Alpha, Red, Green & Blue values
End If

Just a thought
Jay


"Cor Ligthert" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Dennis,
>
> As alternative
> If mycolor.ToArgb = mycolor.Empty.ToArgb
>
> End if
>
> Cor
>
> "Dennis" <(E-Mail Removed)>:
>>
>> public mycolor as color = color.Empty
>>
>> I want to check to see if the user has specified a color like;
>>
>> if mycolor = Color.Empty then.....
>> or
>> if mycolor is Color.Empty then .......
>>
>> I get errors saying that = can be used for colors and is can't be used
>> with
>> value types. I give up...how do I do this. Thanks.
>> --
>> Dennis in Houston
>
>

Jay,

It was just an alternative, this one is not real very important for me,
however I like more evaluating for equality using the = operator than
evaluating using a methode and with the color that is possible.

But the "Is" in this functions tells it very good, therefore it is not
really that important for me.

However as I said, just an alternative.

Cor

"Jay B. Harlow [MVP - Outlook]" <(E-Mail Removed)>

> Cor (& Herfried),
> As I stated in my initial reply:
>
>> See the Color.Equals function in the online help for some important
>> remarks about using Color.Equals and when you may want to use
>> Color.ToArgb to compare two colors.
>
> If I want to compare what is visible seen I will use Color.ToArgb in other
> words to compare the Alpha, Red, Green & Blue values.
>
> If I want to compare what is literally used I will use Color.Equals or
> Color.op_Equality, in other words to compare the names of the color or the
> values for unnamed colors.
>
> For example:
>
> Dim color1 As Color = Color.Black
> Dim color2 As Color = Color.FromArgb(0,0,0)
>
> Both are visibly Black, however they are not logically the same value. In
> other words:
>
> If color1.Equals(color2) Then
> ' color1 is the same named color as color2
> End If
>
> If color1.ToArgb() = color2.ToArgb() Then
> ' color1 & color2 have the same Alpha, Red, Green & Blue values
> End If
>
> Just a thought
> Jay
>
>
> "Cor Ligthert" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Dennis,
>>
>> As alternative
>> If mycolor.ToArgb = mycolor.Empty.ToArgb
>>
>> End if
>>
>> Cor
>>
>> "Dennis" <(E-Mail Removed)>:
>>>
>>> public mycolor as color = color.Empty
>>>
>>> I want to check to see if the user has specified a color like;
>>>
>>> if mycolor = Color.Empty then.....
>>> or
>>> if mycolor is Color.Empty then .......
>>>
>>> I get errors saying that = can be used for colors and is can't be used
>>> with
>>> value types. I give up...how do I do this. Thanks.
>>> --
>>> Dennis in Houston
>>
>>
>
>

Cor,
> It was just an alternative, this one is not real very important for me,

Obviously I know its an alternative, Hopefully you noticed that I stated
last night it was an alternative & again just now.

Thanks for noticing.
Jay



"Cor Ligthert" <(E-Mail Removed)> wrote in message
news:%(E-Mail Removed)...
> Jay,
>
> It was just an alternative, this one is not real very important for me,
> however I like more evaluating for equality using the = operator than
> evaluating using a methode and with the color that is possible.
>
> But the "Is" in this functions tells it very good, therefore it is not
> really that important for me.
>
> However as I said, just an alternative.
>
> Cor
>
> "Jay B. Harlow [MVP - Outlook]" <(E-Mail Removed)>
>
>> Cor (& Herfried),
>> As I stated in my initial reply:
>>
>>> See the Color.Equals function in the online help for some important
>>> remarks about using Color.Equals and when you may want to use
>>> Color.ToArgb to compare two colors.
>>
>> If I want to compare what is visible seen I will use Color.ToArgb in
>> other words to compare the Alpha, Red, Green & Blue values.
>>
>> If I want to compare what is literally used I will use Color.Equals or
>> Color.op_Equality, in other words to compare the names of the color or
>> the values for unnamed colors.
>>
>> For example:
>>
>> Dim color1 As Color = Color.Black
>> Dim color2 As Color = Color.FromArgb(0,0,0)
>>
>> Both are visibly Black, however they are not logically the same value. In
>> other words:
>>
>> If color1.Equals(color2) Then
>> ' color1 is the same named color as color2
>> End If
>>
>> If color1.ToArgb() = color2.ToArgb() Then
>> ' color1 & color2 have the same Alpha, Red, Green & Blue values
>> End If
>>
>> Just a thought
>> Jay
>>
>>
>> "Cor Ligthert" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>>> Dennis,
>>>
>>> As alternative
>>> If mycolor.ToArgb = mycolor.Empty.ToArgb
>>>
>>> End if
>>>
>>> Cor
>>>
>>> "Dennis" <(E-Mail Removed)>:
>>>>
>>>> public mycolor as color = color.Empty
>>>>
>>>> I want to check to see if the user has specified a color like;
>>>>
>>>> if mycolor = Color.Empty then.....
>>>> or
>>>> if mycolor is Color.Empty then .......
>>>>
>>>> I get errors saying that = can be used for colors and is can't be used
>>>> with
>>>> value types. I give up...how do I do this. Thanks.
>>>> --
>>>> Dennis in Houston
>>>
>>>
>>
>>
>
>

Jay,

"Jay B. Harlow [MVP - Outlook]" <(E-Mail Removed)> schrieb:
> For example:
>
> Dim color1 As Color = Color.Black
> Dim color2 As Color = Color.FromArgb(0,0,0)
>
> Both are visibly Black, however they are not logically the same value. In
> other words:
>
> If color1.Equals(color2) Then
> ' color1 is the same named color as color2
> End If
>
> If color1.ToArgb() = color2.ToArgb() Then
> ' color1 & color2 have the same Alpha, Red, Green & Blue values
> End If

That's a valid point, and the way to go depends on the situation.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>