Can I create an anonymous type collection from a DataReader?

Question

I have this code:

var query = \"SELECT * FROM Cats\";

var conn = new SqlConnection(sqlConnectionString);

conn.Open();

var cmd = new SqlCommand(query);
var rea         


        

Answer 1

It's possible, although not particularly neat. We'll need to create a new method that will allow us to create an empty sequence that allows for type inference off of a dummy value for starters:

public static IEnumerable Empty(T dummyValue)
{
    return Enumerable.Empty();
}

This lets us create a list of an anonymous type:

var list = Empty(new
{
    CatName = "",
    CatDOB = DateTime.Today,
    CatStatus = 0
}).ToList();

(The item here isn't used.)

Now we can add our anonymous types to this list:

var cmd = new SqlCommand(query);
var reader = cmd.ExecuteReader();

while (reader.Read())
{
    list.Add(new
    {
        CatName = reader.GetString(0),
        CatDOB = reader.GetDateTime(1),
        CatStatus = reader.GetInt32(2),
    });
}

Of course, using a named type would likely be easier, so I would suggest using one unless there is a real compelling reason not to do so. That is especially true if you plan to use the list outside of the scope it's created in.