Remove C# attribute of a property dynamically

Question

I have a class with a set of properties As given below.

class ContactInfo
{
    [ReadOnly(true)]
    [Category("Contact Info")]
    public string Mobile { get; set; }

    [Category("Contact Info")]
    public string Name{ get; set; }
}

The objects of this class is being assigned to a property grid, so that the users can update an existing contact. you can see that Mobile is marked as ReadOnly.

But, when I want to add an entirely new Contact, I would want the users to be able to edit the contact Mobile also. For that I need to remove the Readonly property dynamically from the Type, before assigning the object to the property grid. Is it possible?

andreialecu · Accepted Answer · 2011-07-04T17:57:51.713

10

You can not remove the attribute at runtime, but you can use reflection to change the ReadOnly attribute's ReadOnly private backing field to False. Making it the equivalent of [ReadOnly(false)]

See this article for details:

http://codinglight.blogspot.com/2008/10/changing-attribute-parameters-at.html

Edit: fixed link

edited Jul 04 '11 at 17:57

answered Mar 20 '10 at 13:31

andreialecu

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Link in answer is dead - *"404 Not Found"*. – Pang Mar 04 '21 at 03:51
1

link is no longer valid – Chase Florell Apr 25 '22 at 21:02
The article is available through the Waback Machine: https://web.archive.org/web/20190907182632/http://codinglight.blogspot.com/2008/10/changing-attribute-parameters-at.html – basiphobe Sep 13 '22 at 14:20

score 2 · Answer 2 · answered Mar 20 '10 at 13:26

2

I have to agree w/ Omu; you're really talking about two classes (view models) in this case, to support your two different views. Something like

CreateContactViewModel and EditContactViewModel

answered Mar 20 '10 at 13:26

Paul

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score 2 · Answer 3 · edited May 10 '23 at 12:52

The CodingLight.com blog moved to blogspot (the above link is broken). See http://codinglight.blogspot.com/2008/10/changing-attribute-parameters-at.html.

Moreover, SysAdmin's followup did not mention the [RefreshProperties(RefreshProperties.All)] attribute that seems to be necessary for an actually-working solution.

Finally, I believe that even David Morton (author of the quoted article) missed one very important thing: if the class (ContactInfo, in SysAdmin's followup example) does not have at least one property with the [ReadOnly] attribute defined at compile time, then when the "isReadOnly" FieldInfo is set to true at runtime the result is that the whole class turns read-only.

New link is also broken. – Jacques Bosch Aug 31 '20 at 08:21 — Jacques Bosch, Aug 31 '20 at 08:21

score 1 · Answer 4 · answered Mar 20 '10 at 13:14

1

it's not possible at the moment to remove attributes dinamycally (at runtime)

as a suggestion you can do 2 classes: one with the attributes and one without

answered Mar 20 '10 at 13:14

Omu

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There's no need to make 2 classes, reflection can be used to modify the boolean field of the ReadOnly attribute and change it to false (not read only). – andreialecu Mar 20 '10 at 13:37

score 0 · Answer 5 · answered Mar 20 '10 at 13:49

I followed up the suggestion by Legenden. Here is what I came up with

class ContactInfo
{
        [ReadOnly(true)]
        [Category("Contact Info")]
        public string Mobile { get; set; }

        [Category("Contact Info")]
        public string Name{ get; set; }

        public void SetMobileEdit(bool allowEdit)
        {
             PropertyDescriptor descriptor =  TypeDescriptor.GetProperties(this.GetType())["Mobile"];

             ReadOnlyAttribute attrib = (ReadOnlyAttribute)descriptor.Attributes[typeof(ReadOnlyAttribute)];

             FieldInfo isReadOnly = attrib.GetType().GetField("isReadOnly", BindingFlags.NonPublic | BindingFlags.Instance);

             isReadOnly.SetValue(attrib, !allowEdit);
        }
}

I think that while this works, it's not a good design. The responsibilities are bleeding. — Paul, Mar 20 '10 at 13:58

score 0 · Answer 6 · answered Mar 30 '23 at 10:02

0

And the original "link" show this:

Now the link won't break again

answered Mar 30 '23 at 10:02

MrCalvin

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Remove C# attribute of a property dynamically

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