UserControl.Property cannot convert to target type...

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Michael Palmer - 29 Apr 2005 20:57 GMT

I have a composite UserControl with a public property with a return type of
a custom enumerator. I want this to show up in the PropertyGrid during
design-time... it will allow me to change the enumeration within the grid,
but when I rebuild it defaults back to the first value in the enumeration
rather than the one I selected during run-time. It also displays "Object
type cannot be converted to target type." in the task list during
design-time.

What am I missing? Thanks!

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"Jeffrey Tan[MSFT]" - 30 Apr 2005 02:50 GMT

Hi Michael,

Thanks for your post!!

Can you show us some detailed information about "I rebuild it defaults back
to the first value in the enumeration"? What does "rebuid default back to
first value" mean? Currently, I think I still does not understand your
problem very well, I suggest you provide some detailed information to help
us reproduce out your issue. Thanks

I have writen a sample code snippet in usercontrol, like this:
public enum EnumTest
{
    item1,
    item2,
    item3,
    item4
}

private EnumTest _prop=EnumTest.item1;
public EnumTest Prop
{
    get
    {
        return _prop;
    }
    set
    {
        _prop=value;
    }
}
I can manipulate this property in PropertyBrowser without any problem. Do
you write a customized TypeConverter inherits from EnumConverter? If so,
you may refer the below link:
http://groups.google.com/groups?hl=zh-CN&lr=&threadm=OgMyycY3BHA.2328%40tkms
ftngp02&rnum=10&prev=/groups%3Fq%3D%2522Object%2Btype%2Bcannot%2Bbe%2Bconver
ted%2Bto%2Btarget%2Btype%2522%2BEnum%26hl%3Dzh-CN%26lr%3D%26selm%3DOgMyycY3B
HA.2328%2540tkmsftngp02%26rnum%3D10

Also, if you got this error when changing the Enum value at runtime,
normally, we should use Enum.Parse method to parse the object value, for
more information, please refer to the link:
http://groups.google.com/groups?hl=zh-CN&lr=&threadm=89BDFF5E-2C24-4B35-97F5
-9ED3BE3CCC9A%40microsoft.com&rnum=9&prev=/groups%3Fq%3D%2522Object%2Btype%2
Bcannot%2Bbe%2Bconverted%2Bto%2Btarget%2Btype%2522%2BEnum%26hl%3Dzh-CN%26lr%
3D%26selm%3D89BDFF5E-2C24-4B35-97F5-9ED3BE3CCC9A%2540microsoft.com%26rnum%3D
9

Note: take care of the link-break.

Anyway, I will wait for your further feedback. Thanks
========================================================
Thank you for your patience and cooperation. If you have any questions or
concerns, please feel free to post it in the group. I am standing by to be
of assistance.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support

Signature

Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

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Michael Palmer - 02 May 2005 14:29 GMT

Hi Jeffrey, thanks for your reply. Using your same code, the default value
for EnumTest would be item1. So, item1 would be the selected value in the
property grid for this UserControl on a form. In the forms designer property
grid, if I change the control's EnumTest property to item2, then rebuild my
project, the forms designer automatically resets my value to item1 and
displays in the task list a design-time error message stating "Object type
cannot be converted to target type." When I remove this property from the
UserControl, I'm no longer given that error message, so I know it stems from
that property.

Also... I'm not using a custom TypeConverter for this property.... I figured
the default EnumConverter would work fine, but maybe I'm doing something
wrong.

Thanks, Jeffrey.

-Michael Palmer

> Hi Michael,
>
[quoted text clipped - 58 lines]
> Get Secure! - www.microsoft.com/security
> This posting is provided "as is" with no warranties and confers no rights.

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Michael Palmer - 02 May 2005 14:51 GMT

Update: upon further testing, when I add an enumerator referenced from
within the same assembly, the problem does not appear, but when I add my
enumerator which is from another assembly, this problem occurs.

> Hi Jeffrey, thanks for your reply. Using your same code, the default value
> for EnumTest would be item1. So, item1 would be the selected value in the
[quoted text clipped - 79 lines]
>> This posting is provided "as is" with no warranties and confers no
>> rights.

Reply to this Message

Michael Palmer - 02 May 2005 15:29 GMT

I found the problem. The enumerator that I declared within my UserControl
was located within the Namespace [Global] within another assembly.
Evidently, this namespace name caused the problem with the forms designer
not being able to persist the selected property value. As soon as I changed
the namespace from [Global] to something else, the problem disappeared.
Problem fixed...

So.... I'm assuming that it's probably best to never have a [Global]
namespace declared anywhere.

-Michael

> Update: upon further testing, when I add an enumerator referenced from
> within the same assembly, the problem does not appear, but when I add my
[quoted text clipped - 86 lines]
>>> This posting is provided "as is" with no warranties and confers no
>>> rights.

Reply to this Message

"Jeffrey Tan[MSFT]" - 03 May 2005 06:39 GMT

Hi Michael,

Cool! I am glad you find the cause to your problem. If you need further
help, please feel free to post. Thanks

Best regards,
Jeffrey Tan
Microsoft Online Partner Support

Signature

Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

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UserControl.Property cannot convert to target type...

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