/BlogEngine/DotNetSlave.BusinessLogic/Providers/DbConnectionHelper.cs

using System;

using System.Collections.Generic;

using System.Configuration;

using System.Configuration.Provider;

using System.Data;

using System.Data.Common;

using System.Linq;

using System.Text;



namespace BlogEngine.Core.Providers

{

    /// <summary>

    /// Helper class for working with DbConnections.

    /// </summary>

    /// <remarks>

    /// 

    /// This class is meant to reduce the amount of repeated code in database provider classes by pulling all the common actions

    /// into one spot. This should remove the many repetitive null checks on connections/parameters.

    /// 

    /// This class handles the creation of DbConnection, setting its connection string, and opening the connection if possible.

    /// 

    /// Usage is simple:

    /// using(var helper = new ConnectionHelper(provider)) {

    ///     if (helper.HasConnection) {

    ///         // do stuff

    ///     }

    /// }

    /// 

    /// Note: This class throws a NullReferenceException if its Provider.CreateParameter() method returns a null object.

    /// All of the methods in the DbBlogProvider class require parameterized queries, and previously each parameter

    /// created was being checked for null before proceeding. It's better to fail fast in this instance, to help creaters

    /// of custom implementations figure out what's wrong.

    /// 

    /// </remarks>

    public sealed class DbConnectionHelper : IDisposable

    {



        #region "Constructors"



        /// <summary>

        /// Creates a new DbConnectionHelper instance from the given ConnectionStringSettings.

        /// </summary>

        /// <param name="settings"></param>

        public DbConnectionHelper(ConnectionStringSettings settings) : this(settings.ProviderName, settings.ConnectionString)

        {

        }



        /// <summary>

        /// Creates a new DbConnectionHelper instance from the given provider name and database connection string..

        /// </summary>

        /// <param name="providerName"></param>

        /// <param name="connectionString"></param>

        public DbConnectionHelper(string providerName, string connectionString)

        {

            this._dbProvFactory = DbProviderFactories.GetFactory(providerName);

            this._connection = this._dbProvFactory.CreateConnection();



            this._hasConnection = (this._connection != null);

            if (this._hasConnection)

            {

                this._connection.ConnectionString = connectionString;

                this._connection.Open();

            }

        }



        #endregion



        #region "Properties"



        /// <summary>

        /// Returns the DbConnection of this instance.

        /// </summary>

        public DbConnection Connection

        {

            get { return this._connection; }

        }

        private DbConnection _connection;



        /// <summary>

        /// Gets whether the Connection of this ConnectionHelper instance is null.

        /// </summary>

        public bool HasConnection

        {

            get { return this._hasConnection; }

        }



        private bool _hasConnection;



        /// <summary>

        /// Gets the DbProviderFactory used by this ConnectionHelper instance.

        /// </summary>

        public DbProviderFactory Provider

        {

            get { return this._dbProvFactory; }

        }

        private DbProviderFactory _dbProvFactory;



        #endregion



        #region "Methods"



        private void CheckDisposed()

        {

            if (this.isDisposed)

            {

                throw new ObjectDisposedException("ConnectionHelper");

            }

        }



        /// <summary>

        /// Uses this ConnectionHelper instance's connection to create and return a new DbCommand instance.

        /// </summary>

        /// <returns></returns>

        public DbCommand CreateCommand()

        {

            this.CheckDisposed();

            return this.Connection.CreateCommand();

        }



        /// <summary>

        /// Users this ConnectionHelper instance's connection to create and return a new DbCommand with the given command text. CommandType is automatically set to CommandType.Text.

        /// </summary>

        /// <param name="commandText"></param>

        /// <returns></returns>

        public DbCommand CreateTextCommand(string commandText)

        {

            var command = this.CreateCommand();

            command.CommandText = commandText;

            command.CommandType = CommandType.Text;



            return command;

        }





        /// <summary>

        /// Uses this ConnectionHelper's Provider to create a DbParameter instance with the given parameter name and value.

        /// </summary>

        /// <param name="parameterName">The name of the parameter.</param>

        /// <param name="value">The value of the parameter.</param>

        /// <returns></returns>

        public DbParameter CreateParameter(string parameterName, object value)

        {

            this.CheckDisposed();



            var param = this.Provider.CreateParameter();



            if (param == null)

            {

                throw new NullReferenceException("DbBlogProvider");

            }

            else

            {

                param.ParameterName = parameterName;

                param.Value = value;

                return param;

            }



        }



        #endregion



        #region "IDisposable"



        private bool isDisposed;



        private void Dispose(bool disposing)

        {

            try

            {

                if (!this.isDisposed && disposing)

                {

                    if (this._connection != null)

                    {

                        this._connection.Dispose();

                    }

                }

            }

            finally

            {

                this._dbProvFactory = null;

                this._connection = null;

                this._hasConnection = false;

                this.isDisposed = true;

            }

        }



        /// <summary>

        /// Disposes this DbConnectionHelper and its underlying connection.

        /// </summary>

        public void Dispose()

        {

            this.Dispose(true);

            GC.SuppressFinalize(this);

        }



        #endregion



    }

}