EF Core insert null value to nullable column that has default value

问题

I am curious about specific scenario in SQL when using EF Core. For example there is a column that allows null and at the same time has defalut value, it is unusual situation but that is not the issue here. Question is about technical possibility.

[SomeId] [uniqueidentifier] NULL DEFAULT (newsequentialid())

And in Application there is Entity(Code First) which has appropriate Property

public Guid? SomeId { get; set; }

The problem is how to Insert this Entity into DB so that SomeId would have Null value. Because even when property is Null, Database will override it with default value.

This can be done with pure sql by explicitly assigning null to column but it seems that the same can't be done with EF, or am I wrong ?

EDIT: To elaborate more

public class ExampleTable
{
    [Key]
    int Id { get; set; }

    string Name { get; set; }

    Guid? SomeId { get; set; }
}

In Seed method for example:

var record1 = new ExampleTable
{
    FirstName = "Carson"
}
var record2 = new ExampleTable
{
    FirstName = "Carson",
    SomeId = null
}
context.ExampleTableSet.Add(record1);
context.ExampleTableSet.Add(record2);
context.SaveChanges(record);

record 1 and 2 are the same since SomeId is nullable Guid?, and in both cases after Submiting SomeId in database gets real value from newsequentialid. Is there any way to keep SomeId Null in database as well.

回答1:

I'm not sure if I understand the question fully, but by modifying your declaration you can set the default value. On creation of a record, 'SomeId' will default to NULL

    public class ExampleTable
    {
        public ExampleTable()
        {
            SomeId = null;
        }

        public Guid? SomeId { get; set; }
    }

来源：https://stackoverflow.com/questions/41969303/ef-core-insert-null-value-to-nullable-column-that-has-default-value