Question

I am creating a model for users and I want that property joined was set to Now(). Here’s my code:

[DefaultValue(DateTime.Now)]
public DateTime joined {get; set;}

I get error:

An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type.

What am I doing wrong? And what’s the best way to do what I want?

Answer 1

DateTime.Now is not a constant, but a property that’s computed at runtime, which is why you can’t do what you’re suggesting.

You can do what you’re proposing with either:

public class MyClass {
  public DateTime joined { get; set; }
  public MyClass() {
    joined = DateTime.Now;
  }
}

Or:

public class MyClass {
  private DateTime _joined = DateTime.Now;
  public DateTime joined { get { return _joined; } set { _joined = value; } }
}