Question

I have a custom class called Rows that implements IEnumerable<Row>. I often use LINQ queries on Rows instances:

Rows rows = new Rows { row1, row2, row3 };
IEnumerable<Row> particularRows = rows.Where<Row>(row => condition);

What I would like is to be able to do the following:

Rows rows = new Rows { row1, row2, row3 };
Rows particularRows = (Rows)rows.Where<Row>(row => condition);

However, I get a “System.InvalidCastException: Unable to cast object of type ‘WhereEnumerableIterator1[NS.Row]’ to type ‘NS.Rows'”. I do have a Rows constructor taking IEnumerable<Row>, so I could do:

Rows rows = new Rows { row1, row2, row3 };
Rows particularRows = new Rows(rows.Where<Row>(row => condition));

This seems bulky, however, and I would love to be able to cast an IEnumerable<Row> to be a Rows since Rows implements IEnumerable<Row>. Any ideas?

Answer 1

extension method to the rescue.

public static Rows ToRows(this IEnumerable<Row> source)
{
  return new Rows(source);
}

Rows particularRows = rows.Where(…).ToRows();

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“Casting” is not a good fit for the problem. Every Rows is an IEnumerable<Row>, but not every IEnumerable<Row> is a Rows