How to Return Anonymous Types from LINQ to SQL Queries?

LINQ to SQL query method of returning anonymous types

When using Linq to SQL to process multiple tables, returning anonymous types may encounter challenges. Please consider the following example:

Original method:

This method successfully retrieve all dog information. However, if we try to retrieve dogs and its variety names:

<code class="language-csharp">public IQueryable<dog> GetDogs()
{
    var db = new DogDataContext(ConnectString);
    var result = from d in db.Dogs
                 join b in db.Breeds on d.BreedId equals b.BreedId
                 select d;
    return result;
}</code>

We will encounter errors because the compiler expects to return the DOG type, not anonymous type.

<code class="language-csharp">public IQueryable<dog> GetDogsWithBreedNames()
{
    var db = new DogDataContext(ConnectString);
    var result = from d in db.Dogs
                 join b in db.Breeds on d.BreedId equals b.BreedId
                 select new
                        {
                            Name = d.Name,
                            BreedName = b.BreedName
                        };
    return result;
}</code>

Alternative method: custom class

A solution is to create a custom class, such as Dogwithbreed:

Then you can modify the code as follows:

<code class="language-csharp">public class DogWithBreed
{
    public Dog Dog { get; set; }
    public string BreedName { get; set; }
}</code>

This method provides a type of safe and reusable solution, although it requires additional coding work. Choosing a custom class can avoid the type of types of anonymous types that do not match, and improve the maintenance and readability of the code.

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