How to Manually Set Primary Key Values in Entity Framework?

Entity Framework: Manual Primary Key Management

Entity Framework (EF) typically auto-generates primary key values. However, situations arise where manually specifying primary keys is necessary. This guide details how to achieve this.

Disabling Automatic Key Generation

To enable manual primary key entry, modify the OnModelCreating method as follows:

<code class="language-csharp">modelBuilder.Entity<Event>().Property(e => e.EventID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);</code>

Addressing Identity Column Conflicts

The error "Identity column cannot insert explicit value" arises when the table's IDENTITY_INSERT property is set to OFF. To rectify this, temporarily set IDENTITY_INSERT to ON before inserting data.

Attribute-Based Configuration

Alternatively, use attributes to define key properties directly within your class:

<code class="language-csharp">[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int EventID { get; set; }</code>

This method avoids modifying OnModelCreating and is compatible with EF Core.

Updated POCO Class Example

The following POCO class demonstrates the attribute-based approach:

<code class="language-csharp">public class Event
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int EventID { get; set; }

    public string EventType { get; set; } 
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }

    public virtual ICollection<Match> Matches { get; set; }
    public virtual ICollection<EventParticipation> EventParticipation { get; set; }
}</code>

This approach offers a cleaner, more maintainable solution for managing manually-set primary keys in your EF models.

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