How to Fix the 'ObjectContext Instance Has Been Disposed' Exception in Entity Framework?

Troubleshooting the "ObjectContext Instance Has Been Disposed" Exception in Entity Framework

Encountering the error "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection"? This guide provides a solution.

Root Cause:

Entity Framework's default lazy-loading mechanism is often the culprit. With lazy loading enabled, navigation properties are marked as virtual, allowing EF to create proxy classes that handle loading related data on demand.

Understanding the Problem:

Let's illustrate with an example:

<code class="language-csharp">public class MemberLoan
{
   public string LoandProviderCode { get; set; }
   public virtual Membership Membership { get; set; }
}</code>

EF generates a proxy class extending MemberLoan. This proxy retains a DbContext reference to lazily load the Membership property. The issue arises when:

1. A using block for the DbContext is used.
2. Entities with lazy-loaded properties are returned outside the using block.
3. Later, an attempt is made to access a lazy-loaded property.

The DbContext is disposed before the lazy-loaded property is accessed, leading to the "ObjectDisposedException".

The Solution: Eager Loading

The preferred solution is eager loading. Instead of relying on lazy loading, preload the necessary navigation properties:

<code class="language-csharp">IQueryable<MemberLoan> query = db.MemberLoans.Include(m => m.Membership);</code>

This approach loads all memberships upfront, preventing the exception.

Further Reading:

For a deeper dive, consult Microsoft's documentation on loading related entities: https://www.php.cn/link/7515989d1c2f94c0cf8c5e4aefd3d12b

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