MVC 5: Code First Approach - Primary Key

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C#

public class ExpenseModel
{
   public int id { get; set; }
   public string reason { get; set; }
   public decimal price { get; set; }
   public DateTime dtCreated { get; set; }
}

I have written a model.

The Entity Framework(EF) Code First model will create a database and table with 'id' as primary key.

My questions are
1.how EF decided that 'id' will be primary key?
2.What to write if want to set another column as primary key?
3.How can i set composite key?
4.How can i set a primary key as an auto-increment?

All the above questions are w.r.t to EF Code First model

Posted 19-Feb-14 3:45am

markand911

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Guruprasad.K.Basavaraju · Answer 1 · 2014-04-01T16:35:00

ANSWER #1.

Entity Framework will infer that because the property is called Id.

ANSWER #2.

Use the [key] annotation

C#

public class ExpenseModel
{
   [KEY]
   public int id { get; set; }
   public string reason { get; set; }
   public decimal price { get; set; }
   public DateTime dtCreated { get; set; }
}

ANSWER #3.

Below is how you get a composite Key

C#

public class ExpenseModel
{
   [Key, Column(Order = 0)]
   public int id { get; set; }
   [Key, Column(Order = 1)]
   public string reason { get; set; }
   public decimal price { get; set; }
   public DateTime dtCreated { get; set; }
}

ANSWER #4.

C#

public class ExpenseModel
{
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int id { get; set; }
   public string reason { get; set; }
   public decimal price { get; set; }
   public DateTime dtCreated { get; set; }
}