Setting the default value of a DateTime Property

Question

I’m using the below code to set default date to the field DateCreated.

public DateTime DateCreated
{
get
{
return this.dateCreated.HasValue
? this.dateCreated.Value
: DateTime.Now;
}

set { this.dateCreated = value; }
}

private DateTime? dateCreated = null;

After executing the command „update-database“ the entity framework gives such error:
InvalidOperationException: Nullable object must have a value.
Where is the problem?

Answer 1

I would like to solve the problem in the level of Model properties.

I recommend following standards patterns and practices and creating a table constraint as illustrated in the reference documentation.

However, if you really need to do this in C# then set the value in the class constructor.

public class DefaultDemo  
{  
    public DefaultDemo()  
    {  
        DateCreated = DateTime.Now;  
    }  
    public DateTime DateCreated { get; set; }  
}  

Constructors (C# programming guide)

Or assign the value.

public DateTime? DateCreated { get; set; } = DateTime.Now;  

If your logic has a CreateDate to assign you can simply assign the date to override the default set in code.

Answer 2

Please read the official documentation which covers configuring default values in EF Core.

https://learn.microsoft.com/en-us/ef/core/modeling/generated-properties?tabs=data-annotations#datetime-value-generation