I want to analyse in this post how Entity Framework really interact with the database. i.e. The queries that are really executed.

In previous post I created a database using Code First. These are two of my entities:

A food representation:

public class Food
{
    /// <summary>
    /// Gets or sets the food identifier.
    /// </summary>
    [Key]
    // NOTE: As the name is className + id, this property is not needed
    public int Id { get; set; }
 
    /// <summary>
    /// Gets or sets the food name.
    /// </summary>
    [MaxLength(200)]
    [Index(IsUnique = true)]
    public string Name { get; set; }
 
    /// <summary>
    /// Gets or sets the recipes needing this Food
    /// </summary>
    // NOTE: EF needs the virtual attribute to enable Lazy loading 
    public virtual List<Recipe> RecpiesNeedingThisFood { get; set; }
 
    /// <summary>
    /// Returns a <see cref="System.String" /> that represents this instance.
    /// </summary>
    public override string ToString()
    {
        return string.Format("{0} ({1})", this.Name, this.Id);
    }
}

An entry on my fridge representation: a food and an expire date of this food.

public class FridgeEntry
{
    /// <summary>
    /// Initializes a new instance of the <see cref="FridgeEntry"/> class.
    /// </summary>
    public FridgeEntry()
    {
        ExpireDate = DateTime.MaxValue;
    }
 
    public int Id { get; set; }
 
    [Required]
    // NOTE virtual is needed for lazy loading
    public virtual Food Food { get; set; }
 
    /// <summary>
    /// Gets or sets the expire date.
    /// </summary>
    public DateTime ExpireDate { get; set; }
 
 
    /// <summary>
    /// Returns a <see cref="System.String" /> that represents this instance.
    /// </summary>
    public override string ToString()
    {
        return string.Format("FoodId ({0}) - expire date: {1}", this.Id, this.ExpireDate);
    }
}

How to debug the queries and connections between EF and my database?

A new feature of EF6 is the possibility to log everything that Entity Framework is doing.

The context.Database has a Log property which is type Action<string> if this action is not null EF will call it always he connect to the database.

Define a logger, to analyse the Lazy loading a simple method writing in console the messages is enough:

private static void ConsoleLogger(string msg)
{
    msg = msg.Trim();
 
    if (!string.IsNullOrEmpty(msg))
    {
        Console.ForegroundColor = ConsoleColor.DarkGray;
        Console.WriteLine(DateTime.Now.TimeOfDay.ToString("g"));
        Console.ForegroundColor = ConsoleColor.DarkGreen;
        Console.WriteLine(msg);
 
        Console.ResetColor();
    }
}

Now we just have to define this  logger as the logger of the context.Database.

EF Lazy loading testing

We have already a way to see the connections between EF and the database, now let’s analyse it:

Continue reading →