Setting the default value of a DateTime Property to DateTime.Now inside the System.ComponentModel Default Value Attrbute

Question

Does any one know how I can specify the Default value for a DateTime property using the System.ComponentModel DefaultValue Attribute?

for example I try this:

Answer 1

I faced the same issue, but the one which works for me best is below:

public DateTime CreatedOn { get; set; } = DateTime.Now;

Answer 2

I know this post is a little old, but a have a suggestion that may help some.

I used an Enum to determine what to set in the attribute constructor.

Property declaration :

[DbProperty(initialValue: EInitialValue.DateTime_Now)]
public DateTime CreationDate { get; set; }

Property constructor :

Public Class DbProperty Inherits System.Attribute

    Public Property InitialValue As Object

    Public Sub New(ByVal initialValue As EInitialValue)
       Select Case initialValue
          Case EInitialValue.DateTime_Now
             Me.InitialValue = System.DateTime.Now

          Case EInitialValue.DateTime_Min
             Me.InitialValue = System.DateTime.MinValue

          Case EInitialValue.DateTime_Max
             Me.InitialValue = System.DateTime.MaxValue

       End Select

    End Sub
End Class

Enum :

Public Enum EInitialValue
   DateTime_Now
   DateTime_Min
   DateTime_Max
End Enum

Answer 3

I think you can do this using StoreGeneratedPattern = Identity (set in the model designer properties window).

I wouldn't have guessed that would be how to do it, but while trying to figure it out I noticed that some of my date columns were already defaulting to CURRENT_TIMESTAMP() and some weren't. Checking the model, I see that the only difference between the two columns besides the name is that the one getting the default value has StoreGeneratedPattern set to Identity.

I wouldn't have expected that to be the way, but reading the description, it sort of makes sense:

Determines if the corresponding column in the database will be auto-generated during insert and update operations.

Also, while this does make the database column have a default value of "now", I guess it does not actually set the property to be DateTime.Now in the POCO. This hasn't been an issue for me as I have a customized .tt file that already sets all of my date columns to DateTime.Now automatically (it's actually not hard to modify the .tt file yourself, especially if you have ReSharper and get a syntax highlighting plugin. (Newer versions of VS may already syntax highlight .tt files, not sure.))

The issue for me was: how do I get the database column to have a default so that existing queries that omit that column will still work? And the above setting worked for that.

I haven't tested it yet but it's also possible that setting this will interfere with setting your own explicit value. (I only stumbled upon this in the first place because EF6 Database First wrote the model for me this way.)

Answer 4

I have tested this on EF core 2.1

Here you cannot use either Conventions or Data Annotations. You must use the Fluent API.

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(b => b.Created)
            .HasDefaultValueSql("getdate()");
    }
}

Official doc

Answer 5

It is possible and quite simple:

for DateTime.MinValue

[System.ComponentModel.DefaultValue(typeof(DateTime), "")]

for any other value as last argument of DefaultValueAttribute specify string that represent desired DateTime value.

This value must be constant expression and is required to create object (DateTime) using TypeConverter.

Answer 6

using System.ComponentModel.DataAnnotations.Schema;

[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public DateTime CreatedOn { get; private set; }