Question

I need to use Linq on any IDataReader implementations like this

var c = sqlDataReader.AsEnumerable().Count();

Example:

public abstract class Test
{
    public abstract SqlDataReader GetSqlDataReader();

    public void Foo()
    {
        SqlDataReader sqlDataReader = GetSqlDataReader();
        IEnumerable<SqlDataReader> sqlEnumerable = sqlDataReader.AsEnumerable();
        var c = sqlEnumerable.Count();
        var s = sqlEnumerable.Sum();
        SqlDataReader first = sqlEnumerable.First();
        var t = first.GetSqlXml(10);
    }
}

What is the best way to write this.
Please, write your snippet.

Answer 1

Try, this:

public static class DataReaderExtension
{
    public class EnumeratorWrapper<T>
    {
        private readonly Func<bool> moveNext;
        private readonly Func<T> current;

        public EnumeratorWrapper(Func<bool> moveNext, Func<T> current)
        {
            this.moveNext = moveNext;
            this.current = current;
        }

        public EnumeratorWrapper<T> GetEnumerator()
        {
            return this;
        }

        public bool MoveNext()
        {
            return moveNext();
        }

        public T Current
        {
            get { return current(); }
        }
    }

    private static IEnumerable<T> BuildEnumerable<T>(
            Func<bool> moveNext, Func<T> current)
    {
        var po = new EnumeratorWrapper<T>(moveNext, current);
        foreach (var s in po)
            yield return s;
    }

    public static IEnumerable<T> AsEnumerable<T>(this T source) where T : IDataReader
    {
        return BuildEnumerable(source.Read, () => source);
    }
}