DefaultValue attribute is not working with my Auto Property

Question

I have the following Auto Property

[DefaultValue(true)]
public bool RetrieveAllInfo { get; set; }

when I try to use it inside the code i find the default false for is false I assume this is the default value to a bool variable, does anyone have a clue what is wrong!?

Solution 1

The DefaultValue attribute is only used to tell the Visual Studio Designers (for example when designing a form) what the default value of a property is. It doesn't set the actual default value of the attribute in code.

More info here: http://support.microsoft.com/kb/311339

Solution 2

[DefaultValue] is only used by (for example) serialization APIs (like XmlSerializer), and some UI elements (like PropertyGrid). It doesn't set the value itself; you must use a constructor for that:

public MyType()
{
    RetrieveAllInfo = true;
}

or set the field manually, i.e. not using an automatically implemented-property:

private bool retrieveAllInfo = true;
[DefaultValue(true)]
public bool RetrieveAllInfo {
    get {return retrieveAllInfo; }
    set {retrieveAllInfo = value; }
}

---

Or, with more recent C# versions (C# 6 or above):

[DefaultValue(true)]
public bool RetrieveAllInfo { get; set; } = true;

Comments

[marbel82]

Similar question. In VS2015: public bool RetrieveAllInfo { get; set; } = true; It's C# 6 feature.

[Ahmed Magdy]

Thank you Philippe, so I think the only solution is from the constructor. thanks

[Admin]

This is dangerous and shouldn't be used. This sets the properties of derived classes before the base class constructor has finished, before the derived class has had a chance to set up anything needed to make the property setters work.

[KOGRA]

Hello its old question. But is it safe for code generation that use only auto-implemented property now? and remove the retreiveAllInfo field? I mean public bool RetreiveAllInfo {get;set;} = true directly? Why I still see most UI libraries use old fashion.

[Marc Gravell]

@KOGRA "yes, that's fine", and "because like this answer: they were written when that syntax didn't exist" (this is the "auto property initializer" feature in C# 6)