How to map column and entity propery of different datatypes in entity framework code first

Question

I am using Entity Framework 5 - Code first.

I have a database that I am connecting to that already exists for some time now (I did not create it). There is a table

Answer 1

The simplest solution is to use another field that will be mapped to the database field, and the ID property will read/write to this field. Something like this:

public class Customer : IEntity
{
   public decimal CustomerID {get; set;}

   [NotMapped]
   public int Id 
   { 
      get { return (int)CustomerID; }
      set { CustomerID = (int)value; } 
   }

   public string FirstName { get; set; }

   public string LastName { get; set; }
}

Map this new field to the database field, using

this.Property(x => x.CustomerID).HasColumnName("Customer_id");

and the EF will use the customer id field, and your code could happily use the integer id field.

Answer 2

Specify numeric type for column

Property(x => x.Id).HasColumnName("Customer_id").HasColumnType("numeric");

When generating database, it will create numeric column with precision 18,0. But when you are mapping to existing database, it will work fine with 5,0 numeric column.

Answer 3

In .Net Core you can also use System.ComponentModel.DataAnnotations.Schema.ColumnAttribute to annotate the property with the underlying column type, e.g.,

    [Column(TypeName = "numeric(5, 0), not null")]
    public int Id { get; set; }

Or if the column is nullable:

    [Column(TypeName = "numeric(5, 0), null")]
    public int? Id { get; set; }

I prefer this to the accepted answer by @Sergey Berezovskiy, as you make the annotation actually on the model, not in elsewhere (in the DbContext).

The ColumnAttribute can also be used to map a property to a column with a different name, e.g.,

    [Column("Identifier", TypeName = "numeric(5, 0), not null")]
    public int Id { get; set; }

The ColumnAttribute may also work in the .Net Framework - I have not tested it.

Answer 4

Another option to work out what the code first should be is to the MS EF Powertools http://visualstudiogallery.msdn.microsoft.com/72a60b14-1581-4b9b-89f2-846072eff19d

You can add an empty project, right click, EF Reverse engineer code first from DB.

You often (not always) get a good start to the solution. Did you try using decimal?

public class Customer : IEntity
{
 public decimal Id { get; set; }

 public string FirstName { get; set; }

 public string LastName { get; set; }
}

if you are concerned precision, you should add validation to the POCO.

There are also some interesting Anotation hacks you may like. http://geekswithblogs.net/danemorgridge/archive/2010/12/20/ef4-code-first-control-unicode-and-decimal-precision-scale-with.aspx good luck

Answer 5

You can convert it to an int with:

 int myInt = Convert.Int32(numberFromDatabase);