How to Efficiently Retrieve Nested Properties Using Entity Framework's Include Method?

Mastering Nested Property Retrieval in Entity Framework

Entity Framework's Include() method simplifies eager loading of related entities. However, fetching deeply nested properties requires a more sophisticated approach.

The Challenge: Partial Object Hydration

Consider this scenario: you're retrieving ApplicationServers and need the fully populated ApplicationsWithOverrideGroup property, including its nested Application and CustomVariableGroup properties. A simple Include() call might fall short:

<code class="language-csharp">public IEnumerable<applicationserver> GetAll()
{
    return this.Database.ApplicationServers
        .Include(x => x.ApplicationsWithOverrideGroup)                
        ...
        .ToList();
}</applicationserver></code>

This only loads the Enabled property of ApplicationWithOverrideVariableGroup, leaving Application and CustomVariableGroup unpopulated.

The Solution: Efficient Nested Loading

To resolve this, leverage nested Include() calls (EF6) or the ThenInclude() method (EF Core):

Entity Framework 6:

Employ the Select() method with lambda expressions for nested property inclusion:

<code class="language-csharp">query.Include(x => x.Collection.Select(y => y.Property))</code>

Entity Framework Core:

Utilize the ThenInclude() method for a cleaner, more readable solution:

<code class="language-csharp">query.Include(x => x.Collection)
     .ThenInclude(x => x.Property);</code>

These techniques ensure complete object hydration, providing all the necessary nested data within your retrieved entities. This eliminates the need for subsequent database queries, optimizing performance and data retrieval.

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