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

You can create helper generic method and let compiler infer type parameter:

private IEnumerable Select(DbDataReader reader, Func selector)
{
    while(reader.Read())
    {
        yield return selector(reader);
    }
}

usage:

var items = SelectFromReader(reader, r => new { CatName = r.GetString(0), CarDOB = r.GetDateTime(1), CatStatus = r.GetInt32(2) });

You can even make the method an extension method on DbDataReader:

public static IEnumerable Select(this DbDataReader reader, Func selector)
{
    while (reader.Read())
    {
        yield return selector(reader);
    }
}

and use it like that:

var items = reader.Select(r => new { CatName = r.GetString(0), CarDOB = r.GetDateTime(1), CatStatus = r.GetInt32(2) });