How to Prevent Entity Framework from Automatically Generating Primary Keys?

Suppressing Automatic Primary Key Generation in Entity Framework

Entity Framework's code-first approach often automatically generates primary keys, specifically auto-incrementing identity columns. This automatic behavior isn't always suitable. This article outlines how to override this default functionality.

One common approach uses fluent API configuration:

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

However, this can lead to the error: "Cannot insert explicit value for identity column in table 'Events' when IDENTITY_INSERT is set to OFF."

Understanding the Error

This error arises from a conflict. DatabaseGeneratedOption.None prevents EF from generating IDs, but the database table still possesses the IDENTITY property, creating a clash when trying to manually assign key values.

Resolution

The solution involves disabling the IDENTITY property on the ID column within the database. Use this SQL command:

<code class="language-sql">ALTER TABLE Events ALTER COLUMN EventID INT NOT NULL</code>

Attribute-Based Alternative

Alternatively, you can utilize attributes directly within your entity class:

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

This method also functions correctly with EF Core.

By implementing these solutions, developers gain control over primary key assignment, manually specifying values and bypassing EF's default auto-generation.

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