Can LINQ to SQL Queries Return Anonymous Types as Results?

Can LINQ to SQL return anonymous types as results?

In LINQ to SQL, how to query multiple tables and combine the results with anonymous types?

Initial attempt using anonymous types

The following example, using two tables Dogs and Breeds, attempts to retrieve all dogs and their corresponding BreedName using an 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;
}</dog></code>

However, this fails because the compiler expects Dogs to be returned, not an anonymous type.

Custom type

One solution is to create a custom type to represent the dog with the breed name:

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

Use custom type

Using this custom type, queries can be modified to return the desired results:

<code class="language-csharp">public IQueryable<dogwithbreed> 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 DogWithBreed()
                        {
                            Dog = d,
                            BreedName = b.BreedName
                        };
    return result;
}</dogwithbreed></code>

This approach provides a type-safe and reusable way to combine results from multiple tables using custom types. This avoids the type mismatch problems encountered when using anonymous types.

The above is the detailed content of Can LINQ to SQL Queries Return Anonymous Types as Results?. For more information, please follow other related articles on the PHP Chinese website!