filestore.cs

微软的行业应用解决方案示例

using System;
using System.Linq;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace Microsoft.Mobile.Data
{
    /// <summary>
    /// Implementation of the <see cref="Microsoft.Mobile.Data.DataStore"/> to read 
    /// a file as collection of rows and columns.
    /// </summary>
    public class FileStore : DataStore
    {
        #region Fields
        string _fileName;
        #endregion


        #region Constructor(s) & Dispose
        /// <summary>
        /// Store the connection string. The file is not openned at this time.
        /// </summary>
        /// <param name="connectionString">The name of the file</param>
        public FileStore(string connectionString)
            : base(connectionString)
        {
            _fileName = connectionString;
        }


        /// <summary>
        /// Optional DataStore construction signature which allows for 
        /// implementation specific parameters to be passed to a specific
        /// implementation.
        /// </summary>
        /// <param name="connectionString">
        /// string containing connection information
        /// </param>
        /// <param name="implementationParameters">
        /// implementation specific additional parameters
        /// </param>
        protected FileStore(string connectionString, Parameters implementationParameters)
            : base(connectionString, implementationParameters)
        {
        }

        /// <summary>
        /// Needs to be implemented to since it is abstract
        /// </summary>
        protected override void  Dispose(bool disposing)
        {
        }
        #endregion


        #region Methods
        /// <summary>
        /// Files are not transactional so BeginTransaction not implemented.
        /// </summary>
        public override void BeginTransaction()
        {
            throw new NotImplementedException();
        }


        /// <summary>
        /// Files are not held open so Close not implemented.
        /// </summary>
        public override void Close()
        {
            throw new NotImplementedException();
        }


        /// <summary>
        /// Files are not transactional so Commit not implemented.
        /// </summary>
        public override void Commit()
        {
            throw new NotImplementedException();
        }

        /// <summary>
        /// Opens the file and wraps it in an enumerator.
        /// </summary>
        /// <param name="selector">not used currently</param>
        /// <returns>enumerator to read each line of the file</returns>
        public override RowEnumerator Read(string selector)
        {
            return new EnumerateFile(_fileName);
        }


        /// <summary>
        /// Opens the file and wraps it in an enumerator.
        /// </summary>
        /// <param name="selector">not used currently</param>
        /// <param name="parameters">not used</param>
        /// <returns>enumerator to read each line of the file</returns>
        public override RowEnumerator Read(string selector, 
                                           Parameters parameters)
        {
            return Read(selector);
        }


        /// <summary>
        /// Reads the first line of the file.
        /// </summary>
        /// <param name="selector">not used currently</param>
        /// <returns>contents of the first line of the file</returns>
        public override object GetValue(string selector)
        {
            RowEnumerator row;
            string result = string.Empty;

            row = Read(null);
            if (row.MoveNext())
            {
                result = row.Current["FileValue"].ToString();
            }
            return result;
        }


        /// <summary>
        /// Reads the first line of the file.
        /// </summary>
        /// <param name="selector">not used currently</param>
        /// <param name="parameters">not used</param>
        /// <returns>contents of the first line of the file</returns>
        public override object GetValue(string selector, Parameters parameters)
        {
            return GetValue(null);
        }


        /// <summary>
        /// Files are not transactional so Rollback not implemented.
        /// </summary>
        public override void Rollback()
        {
            throw new NotImplementedException();
        }

        /// <summary>
        /// Writes a line to the end of a file.
        /// </summary>
        /// <param name="update">contents to write to a file</param>
        public override void Save(string update)
        {
            Save(update, null);
        }


        /// <summary>
        /// Writes a line to the end of a file.
        /// </summary>
        /// <param name="update">contents to write to a file</param>
        /// <param name="parameters">not used</param>
        public override void Save(string update, Parameters parameters)
        {
            StringBuilder writeLine;

            writeLine = new StringBuilder(update);
            foreach (KeyValuePair<string, object> currentParameter in parameters)
            {
                writeLine.Replace(currentParameter.Key, currentParameter.Value.ToString());
            }

            (new StreamWriter(_fileName, true)).WriteLine(writeLine);
        }
        #endregion
    }
}