Translate Query Syntax to Extension Methods Syntax

Question

I am trying to stay consistent within my demo app using the AdventureWorks2012 database and EF, but I need some help translating this Linq statement into extension methods.

return (from person in this.context.Persons
        from email in this.context.EmailAddresses
        where email.EmailAddress == emailAddress
        select person).FirstOrDefault();

The objects are:

public class Person
{
    public int BusinessEntityId { get; set; }
    public string PersonType {get;set;}
    public bool NameStyle { get; set; }
    public string Title { get; set; }
    public string FirstName { get; set; }
    public string MiddleName { get; set; }
    public string LastName { get; set; }
    public string Suffix { get; set; }
    public int EmailPromotion { get; set; }
    public PersonPassword Password { get; set; }
    public virtual ICollection<PersonEmailAddress> EmailAddresses { get; set; }
}

public class PersonEmailAddress
{
    public int BusinessEntityId { get; set; }
    public int EmailAddressId { get; set; }
    public string EmailAddress { get; set; }
    public virtual Person Person { get; set; }
}

public class PersonPassword
{
    public int BusinessEntityId { get; set; }
    public string PasswordHash { get; set; }
    public string PasswordSalt { get; set; }
    public virtual Person Person { get; set; }
}

Where the BusinessEntityId is the PK. Any help is greatly appreciated. Thanks...

Daniel A.A. Pelsmaeker · Accepted Answer · 2013-02-22 00:48:33Z

3

Below I'll answer your question exactly. However, I don't really see why you would want to have your query translated to extension methods, so I think this answer is not the answer you're looking for. If so, could you dive into the terminology and rephrase the question?

First: LINQ query syntax is just nice syntactic sugar for extension methods. Your code:

return (from person in this.context.Persons
        from email in this.context.EmailAddresses
        where email.EmailAddress == emailAddress
        select person).FirstOrDefault();

Below is the LINQ query syntax translated to extension methods. The two are equivalent, they do exactly the same and give the same result:

return this.context.Persons
    .SelectMany(p => this.context.EmailAddresses,
        (p, e) => new { Person = p, Email = e})
    .Where(pe => pe.Email == pe.Person)
    .Select(pe => pe.Person)
    .FirstOrDefault();

It is just not as nice to read, and it is harder to understand.

answered Feb 22, 2013 at 0:48

Daniel A.A. Pelsmaeker

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1 Comment

Jesse C. Slicer Over a year ago

It is just not as nice to read, and it is harder to understand. I believe the opposite.

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