Unable to cast object of type 'System.Data.SqlClient.SqlDataReader' to type 'System.Collections.Generic.IEnumerable'

Question

I've been trying to understand why it's giving me this error because I'm not using SqlDataReader, I get that I'm using SQL Server and the Interface is returning the specific type but still I'm telling .NET to use IDataReader instead.

Here's the code:

    public DataSet ExecuteSelectProcedure(string procedure, List<Parameter> parameters)
    {
        conexion.Open();

        try
        {
            IDbCommand command = conexion.CreateCommand();
            command.CommandType = CommandType.StoredProcedure;
            command.Connection = conexion;
            command.CommandText = procedure;

            foreach (var parameter in parameters)
            {
                IDbDataParameter dataParameter = command.CreateParameter();
                dataParameter.Direction = (System.Data.ParameterDirection) parameter.Direction;
                dataParameter.Value = parameter.Value;
                dataParameter.ParameterName = parameter.Name;
                dataParameter.DbType = (DbType) parameter.Type;
                command.Parameters.Add(dataParameter);
            }


            IDataReader result = command.ExecuteReader();
            DataSet dataSet = new DataSet();
            foreach (var table in (IEnumerable<IDataReader>) result)
            {
                DataTable dataTable = new DataTable();
                dataTable.Load(table);
                dataSet.Tables.Add(dataTable);
            }

            result.Close();

            return dataSet;
        }
        finally
        {
            conexion.Close();
        }

The error is when casting IEnumerable on the foreach loop. Thanks in advance...

Answer 1

It is using SqlDataReader, because that's the actual type that command.ExecuteReader is returning. You're then trying to cast that to an IEnumerable<IDataReader>, but it's not clear why. Why did you expect that to work?

You iterate over multiple tables (etc) in an IDataReader by calling NextResult(). For example:

do
{
    // Read the current result; if reading manually, call Read()
    // to get to the next row within the result
} while (reader.NextResult());