Map a Dictionary in Entity Framework Code First Approach

Question

I have a dictionary like this:

/// <summary> /// Gets the leave entitlement details. /// </summary> /// <value>The leave entitlement details.</value> public Dictionary<string, EmployeeLeaveEntitlement> LeaveEntitlementDetails { get; set; }   

And I want to map it to the database. Is it possible to use a protected or private List<> for that? such as:

/// <summary> /// Gets the leave entitlement details. /// </summary> /// <value>The leave entitlement details.</value> public Dictionary<string, EmployeeLeaveEntitlement> LeaveEntitlementDetails { get; set; }   public List<EmployeeLeaveEntitlement> LeveEntitlementStore {     get     {         List<EmployeeLeaveEntitlement> leaveEntitlements = new List<EmployeeLeaveEntitlement>();          foreach (KeyValuePair<string, EmployeeLeaveEntitlement> leaveType in LeaveEntitlementDetails)         {             leaveEntitlements.Add(leaveType.Value);         }          return leaveEntitlements;     }     set     {         foreach (EmployeeLeaveEntitlement item in value)         {             this.LeaveEntitlementDetails.Add(item.LeaveType, item);         }     } } 

Can anyone help me?

Answer 1

Entity Framework does not presently support mapping a Dictionary natively.

See the following for more information and work-arounds:

Entity Framework 4 POCO with Dictionary

EF Code First - Map Dictionary or custom type as an nvarchar

http://social.msdn.microsoft.com/Forums/en-US/adonetefx/thread/a51ba903-2b8b-448e-8677-d140a0b43e89/

Answer 2

EF Core 2.1 introduced a new feature called value conversion:

Value converters allow property values to be converted when reading from or writing to the database.

This feature highly simplifies the serialization approach mentioned in previous answers, which means, the introduction of on an additional "helper" property and the marking of your dictionary property as [NotMapped] becomes unnecessary.

Here are some lines of code tailored to your case (note, I am using Json.NET, but feel free to use your serializer of choice):

using System.Collections.Generic; using Microsoft.EntityFrameworkCore; using Microsoft.EntityFrameworkCore.Metadata.Builders; using Newtonsoft.Json; using Newtonsoft.Json.Serialization;  namespace My.Name.Space {     public class MyEntity     {         public int Id { get; set; }         public Dictionary<string, EmployeeLeaveEntitlement> LeaveEntitlementDetails { get; set; }      }      public class MyEntityConfiguration : IEntityTypeConfiguration<MyEntity>     {         public void Configure(EntityTypeBuilder<MyEntity> builder)         {             builder.ToTable("MyEntity");             builder.HasKey(e => e.Id);              builder             .Property(e => e.LeaveEntitlementDetails)             .IsRequired()             .HasConversion(                 v => JsonConvert.SerializeObject(v),                 v => v == null                     ? new Dictionary<string, EmployeeLeaveEntitlement>() // fallback                     : JsonConvert.DeserializeObject<Dictionary<string, EmployeeLeaveEntitlement>>(v)             );         }     } }