Entity Framework Core 使用 UDF 定义属性

Question

New to EF and have the following scenario. I've created a couple of very basic tables/classes to demonstrate what I want to achieve (excuse any potential spelling issues that may be present below, I've just typed this out as an example).

   //Model Class
    public class Customer{
        public long Id{ get; private set; }
        public string name{ get; private set; }
        public long status{ get; private set; }
    }

//configuration
public class CustomerConfiguration : IEntityTypeConfiguration<Customer>
{
    public void Configure(EntityTypeBuilder<Customer> builder)
    {
        builder.ToTable("Customer");

        builder.HasKey(e => e.Id);

        builder.Property(e => e.Id)
            .HasColumnName("Id")
            .ValueGeneratedNever()
            .IsRequired();

        builder.Property(e => e.name)
            .HasColumnName("name")
            .IsRequired();

    }
}

//Tables
CREATE TABLE [dbo].[Customer](
    [Id] [uniqueidentifier] NOT NULL,
    [name] [nvarchar](255) NOT NULL )


CREATE TABLE [dbo].[CustomerJournal](
    [Id] [bigint] NOT NULL,
    [RowId] [int] IDENTITY(1,1) NOT NULL,
    [CustomerId] [bigint] NOT NULL,
    [StatusId] [bigint] NOT NULL,
    [StatusAlias] [varchar](32) NOT NULL,
    [StatusName] [nvarchar](128) NOT NULL,
    [CreateDate] [datetimeoffset](7) NOT NULL
)


ALTER TABLE [dbo].[CustomerJournal]  WITH CHECK ADD  CONSTRAINT [FK_CustomerJournal_Customer] FOREIGN KEY(CustomerId)
REFERENCES [dbo].[Customer] ([Id])
GO

CustomerJournal is a journal of statuses for a customer. I do not have a StatusId on the Customer table, rather I would like to call a UDF to retrieve the latest journal entry.

CREATE Function [dbo].[CustomerStatus](
   @CustomerId BIGINT
)
RETURNS BIGINT
BEGIN
    DECLARE @StatusID BIGINT

    SELECT  
        TOP 1
        @StatusID = [StatusId]
    FROM
        [dbo].[CustomerJournal] WITH (NOLOCK)
    WHERE
        [CustomerId] = @CustomerID
    AND
    ORDER BY
        [RowID] DESC
    
    RETURN @StatusID

END

How could I add a property "status" to my configuration class which passes in my Id into this UDF and retrieves it??

Thanks

Answer 1

You can Add a Calculated Column to your Table and use that:

public class Customer{
    public long Id{ get; private set; }
    public string name{ get; private set; }
    public long status{ get; private set; }
    public long LastJournalEntryId {get;set;}
}

//configuration
public class CustomerConfiguration : IEntityTypeConfiguration<Customer>
{
    public void Configure(EntityTypeBuilder<Customer> builder)
    {
        builder.ToTable("Customer");

        builder.HasKey(e => e.Id);

        builder.Property(e => e.Id)
            .HasColumnName("Id")
            .ValueGeneratedNever()
            .IsRequired();

        builder.Property(e => e.name)
            .HasColumnName("name")
            .IsRequired();

        //"GetLastJournalEntryIdForCustomer" is the name of your UDF
        builder.Property(e => e.LastJournalEntryId)
            .HasComputedColumnSql("GetLastJournalEntryIdForCustomer(Id)");
    }
}

Depending on whether you're using Code-First or DB-First you need to create it in the appropriate place first of course.