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DefaultValue attribute of type color

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Valery
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Valery asked on 03 Jan 2018, 09:13 AM

How do you specify a default value for a Color property using the [DefaultValue()] attribute?

if I write

        [DefaultValue(typeof(Color), "Gray")]
        [DefaultValue(typeof(Color), "0x808080")]

it does not work correctly


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Dess | Tech Support Engineer, Principal
Telerik team
answered on 03 Jan 2018, 09:56 AM
Hello, Valery, 

Thank you for writing.  

The DefaultValueAttribute defines the default value to which the property will be reset. When the property value is set to something different the default value, it will be marked as modified. Here is a sample code snippet demonstrating how to use the default value: 
public RadForm1()
{
    InitializeComponent();
 
    this.radPropertyGrid1.SelectedObject = new Item();
}
 
public class Item
{
    [DefaultValue(5)]
    public int Id { get; set; }
 
    [DefaultValue("Test")]
    public string Name { get; set; }
 
    [DefaultValue(typeof(Color), "Red")]
    public Color BackColor { get; set; }
 
    public Item()
    {
        this.Id = 5;
        this.Name = "Empty";
        this.BackColor = Color.Red;
    }
}




I hope this information helps. Should you have further questions I would be glad to help.
 
Regards,
Dess
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Valery
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answered on 03 Jan 2018, 10:20 AM

            public byte[] HiRgb = { 128, 128, 128 };
            [DefaultValue(typeof(Color), "Gray")]
            public Color HiColor
            {
                get => Color.FromArgb(HiRgb[0], HiRgb[1], HiRgb[2]);
                set
                {
                    HiRgb[0] = value.R; HiRgb[1] = value.G; HiRgb[2] = value.B;
                }
            }

This always marked as modified. Why?


0
Dess | Tech Support Engineer, Principal
Telerik team
answered on 03 Jan 2018, 12:04 PM
Hello, Valery, 

Thank you for writing back. 

Each value that differs from the default value is marked as edited. Note that if you compare Color.Gray and Color.FromArgb(128,128,128) the obtained result will be false. That is why the HiColor is marked as modified. You can set the HiColor value to Color.Gray. Thus, it won't be bold.

I hope this information helps. If you have any additional questions, please let me know. 

 Regards,
Dess
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Valery
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answered on 04 Jan 2018, 03:29 AM

Ok.

How can I change default values during runtime?

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Valery
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answered on 04 Jan 2018, 03:40 AM

PS.

In winforms I use ShouldSerialize and Reset Methods

https://docs.microsoft.com/en-us/dotnet/framework/winforms/controls/defining-default-values-with-the-shouldserialize-and-reset-methods

Is there an analog in your program?

0
Dess | Tech Support Engineer, Principal
Telerik team
answered on 04 Jan 2018, 08:37 AM
Hello, Valery, 

Thank you for writing back. 

Note that the metadata in DefaultValueAttribute is retrieved when it is first requested and it is cached for subsequent retrieval. In order to change the attribute value for a specific property at runtime, you can directly modify the property descriptor for the given property. Here is a code snippet demonstrating this: 
AttributeCollection attributes = TypeDescriptor.GetProperties(this.radPropertyGrid1.SelectedObject)["HiColor"].Attributes;
DefaultValueAttribute myAttribute = (DefaultValueAttribute)attributes[typeof(DefaultValueAttribute)];
FieldInfo defaultValueField = (typeof(DefaultValueAttribute)).GetField("value", BindingFlags.Instance | BindingFlags.NonPublic);
defaultValueField.SetValue(myAttribute, Color.Fuchsia);

RadPropertyGrid offers to reset a property to its default value by using the default context menu: 



I hope this information helps. If you have any additional questions, please let me know. 

 Regards,
Dess
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Valery
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answered on 04 Jan 2018, 10:24 AM

I do not need to reset a property to its default value.

I need change default value during runtime. For example, if another property has changed the state machine and i need a different default color.

use of reflection is inconvenient

0
Dess | Tech Support Engineer, Principal
Telerik team
answered on 04 Jan 2018, 10:54 AM
Hello, Valery, 

Thank you for writing back. 

Changing attributes' values is not a usual requirement for RadPropertyGrid users. As it was previously explained, the metadata in DefaultValueAttribute is retrieved when it is first requested and it is cached for subsequent retrieval. It is not expected to be further modified. Currently, the possible solution that I can suggest to use reflection as it is demonstrated in the previous reply.

I hope this information helps. If you have any additional questions, please let me know. 

 Regards,
Dess
Progress Telerik
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Dess | Tech Support Engineer, Principal
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