enumeratedatareader.cs

微软的行业应用解决方案示例

using System;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics.CodeAnalysis;
using System.Text;


namespace Microsoft.Mobile.Data
{
    /// <summary>
    /// Used to enumerate a data reader.
    /// </summary>
    [SuppressMessage("Microsoft.Naming",
                     "CA1710:IdentifiersShouldHaveCorrectSuffix",
                     Justification = "More readable as EnumerateDataReader")]
    public class EnumerateDataReader : RowEnumerator 
    {
        #region Fields
        private IDataReader _dataReader;
        #endregion


        #region Constructor(s) and Dispose
        /// <summary>
        /// Build the enumerator passing in the DataReader to enumerate.
        /// </summary>
        /// <param name="dataReader">DataReader to enumerate</param>
        public EnumerateDataReader(IDataReader dataReader)
        {
            if (dataReader == null)
            {
                throw new ArgumentException("Cannot be null.", "dataReader");
            }

            _dataReader = dataReader;
        }


        /// <summary>
        /// Close and release the DataReader
        /// </summary>
        protected override void  Dispose(bool disposing)
        {
            _dataReader.Close();
            _dataReader.Dispose();
        }
        #endregion


        #region Methods
        /// <summary>
        /// Move forward to the next row.
        /// </summary>
        /// <returns>Returns false if no more rows are present</returns>
        public override bool MoveNext()
        {
            bool result;
            string tempString;
            
            // read a row from the data reader
            result = _dataReader.Read();

            // if a row was read then build a Row
            if (result)
            {
                // build Row current row from DataReader
                currentRow = new DataRow();

                // loop through the fields and building the Columns
                // and add them to the row
                for (int loop = 0; loop < _dataReader.FieldCount; loop++)
                {
                    tempString = _dataReader.GetName(loop);
                    currentRow.Add(tempString, 
                                    _dataReader[loop]);
                }
            }
            else
            {
                // if no more rows set the currentRow to null
                currentRow = null;
            }

            return result;
        }


        /// <summary>
        /// Reset is not implemented since a DataReader is forward only
        /// </summary>
        public override void Reset()
        {
            throw new InvalidOperationException("DataReaders are forward only. Use a different enumerator if you need to start over.");
        }
        #endregion
    }
}