sqlhelper.cs

C#数据库类。

using System;
using System.Data;
using System.Xml;
using System.Data.SqlClient;
using System.Collections;

namespace Touzi.Data
{
	/// <summary>
	/// 为进行 SQLServer 数据库访问而做的封装
	/// </summary>
	public sealed class SqlHelper
	{
        #region private utility methods & constructors

		// Since this class provides only static methods, make the default constructor private to prevent 
		// instances from being created with "new SqlHelper()"
		private SqlHelper() {}

		/// <summary>
		/// This method is used to attach array of SqlParameters to a SqlCommand.
		/// 
		/// This method will assign a value of DbNull to any parameter with a direction of
		/// InputOutput and a value of null.  
		/// 
		/// This behavior will prevent default values from being used, but
		/// this will be the less common case than an intended pure output parameter (derived as InputOutput)
		/// where the user provided no input value.
		/// </summary>
		/// <param name="command">The command to which the parameters will be added</param>
		/// <param name="commandParameters">An array of SqlParameters to be added to command</param>
		private static void AttachParameters(SqlCommand command, SqlParameter[] commandParameters)
		{
			if( command == null ) throw new ArgumentNullException( "command" );
			if( commandParameters != null )
			{
				foreach (SqlParameter p in commandParameters)
				{
					if( p != null )
					{
						// Check for derived output value with no value assigned
						if ( ( p.Direction == ParameterDirection.InputOutput || 
							p.Direction == ParameterDirection.Input ) && 
							(p.Value == null))
						{
							p.Value = DBNull.Value;
						}
						command.Parameters.Add(p);
					}
				}
			}
		}

		/// <summary>
		/// This method assigns an array of values to an array of SqlParameters
		/// </summary>
		/// <param name="commandParameters">Array of SqlParameters to be assigned values</param>
		/// <param name="parameterValues">Array of objects holding the values to be assigned</param>
		private static void AssignParameterValues(SqlParameter[] commandParameters, object[] parameterValues)
		{
			if ((commandParameters == null) || (parameterValues == null)) 
			{
				// Do nothing if we get no data
				return;
			}

			// We must have the same number of values as we pave parameters to put them in
			if (commandParameters.Length != parameterValues.Length)
			{
				throw new ArgumentException("Parameter count does not match Parameter Value count.");
			}

			// Iterate through the SqlParameters, assigning the values from the corresponding position in the 
			// value array
			for (int i = 0, j = commandParameters.Length; i < j; i++)
			{
				// If the current array value derives from IDbDataParameter, then assign its Value property
				if (parameterValues[i] is IDbDataParameter)
				{
					IDbDataParameter paramInstance = (IDbDataParameter)parameterValues[i];
					if( paramInstance.Value == null )
					{
						commandParameters[i].Value = DBNull.Value; 
					}
					else
					{
						commandParameters[i].Value = paramInstance.Value;
					}
				}
				else if (parameterValues[i] == null)
				{
					commandParameters[i].Value = DBNull.Value;
				}
				else
				{
					commandParameters[i].Value = parameterValues[i];
				}
			}
		}

		/// <summary>
		/// This method opens (if necessary) and assigns a connection, transaction, command type and parameters 
		/// to the provided command
		/// </summary>
		/// <param name="command">The SqlCommand to be prepared</param>
		/// <param name="connection">A valid SqlConnection, on which to execute this command</param>
		/// <param name="transaction">A valid SqlTransaction, or 'null'</param>
		/// <param name="commandType">The CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">The stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">An array of SqlParameters to be associated with the command or 'null' if no parameters are required</param>
		/// <param name="mustCloseConnection"><c>true</c> if the connection was opened by the method, otherwose is false.</param>
		private static void PrepareCommand(SqlCommand command, SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters, out bool mustCloseConnection )
		{
			if( command == null ) throw new ArgumentNullException( "command" );
			if( commandText == null || commandText.Length == 0 ) throw new ArgumentNullException( "commandText" );

			// If the provided connection is not open, we will open it
			if (connection.State != ConnectionState.Open)
			{
				mustCloseConnection = true;
				connection.Open();
			}
			else
			{
				mustCloseConnection = false;
			}

			// Associate the connection with the command
			command.Connection = connection;

			// Set the command text (stored procedure name or SQL statement)
			command.CommandText = commandText;

			// If we were provided a transaction, assign it
			if (transaction != null)
			{
				if( transaction.Connection == null ) throw new ArgumentException( "The transaction was rollbacked or commited, please provide an open transaction.", "transaction" );
				command.Transaction = transaction;
			}

			// Set the command type
			command.CommandType = commandType;

			// Attach the command parameters if they are provided
			if (commandParameters != null)
			{
				AttachParameters(command, commandParameters);
			}
			return;
		}

        #endregion private utility methods & constructors

        #region ExecuteNonQuery

		/// <summary>
		/// Execute a SqlCommand (that returns no resultset and takes no parameters) against the database specified in 
		/// the connection string
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders");
		/// </remarks>
		/// <param name="connectionString">A valid connection string for a SqlConnection</param>
		/// <param name="commandType">The CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">The stored procedure name or T-SQL command</param>
		/// <returns>An int representing the number of rows affected by the command</returns>
		public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText)
		{
			// Pass through the call providing null for the set of SqlParameters
			return ExecuteNonQuery(connectionString, commandType, commandText, (SqlParameter[])null);
		}

		/// <summary>
		/// Execute a SqlCommand (that returns no resultset) against the database specified in the connection string 
		/// using the provided parameters
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>
		/// <param name="connectionString">A valid connection string for a SqlConnection</param>
		/// <param name="commandType">The CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">The stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">An array of SqlParamters used to execute the command</param>
		/// <returns>An int representing the number of rows affected by the command</returns>
		public static int ExecuteNonQuery(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
		{
			if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );

			// Create & open a SqlConnection, and dispose of it after we are done
			using (SqlConnection connection = new SqlConnection(connectionString))
			{
				connection.Open();

				// Call the overload that takes a connection in place of the connection string
				return ExecuteNonQuery(connection, commandType, commandText, commandParameters);
			}
		}

		/// <summary>
		/// Execute a stored procedure via a SqlCommand (that returns no resultset) against the database specified in 
		/// the connection string using the provided parameter values.  This method will query the database to discover the parameters for the 
		/// stored procedure (the first time each stored procedure is called), and assign the values based on parameter order.
		/// </summary>
		/// <remarks>
		/// This method provides no access to output parameters or the stored procedure's return value parameter.
		/// 
		/// e.g.:  
		///  int result = ExecuteNonQuery(connString, "PublishOrders", 24, 36);
		/// </remarks>
		/// <param name="connectionString">A valid connection string for a SqlConnection</param>
		/// <param name="spName">The name of the stored prcedure</param>
		/// <param name="parameterValues">An array of objects to be assigned as the input values of the stored procedure</param>
		/// <returns>An int representing the number of rows affected by the command</returns>
		public static int ExecuteNonQuery(string connectionString, string spName, params object[] parameterValues)
		{
			if( connectionString == null || connectionString.Length == 0 ) throw new ArgumentNullException( "connectionString" );
			if( spName == null || spName.Length == 0 ) throw new ArgumentNullException( "spName" );

			// If we receive parameter values, we need to figure out where they go
			if ((parameterValues != null) && (parameterValues.Length > 0)) 
			{
				// Pull the parameters for this stored procedure from the parameter cache (or discover them & populate the cache)
				SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connectionString, spName);

				// Assign the provided values to these parameters based on parameter order
				AssignParameterValues(commandParameters, parameterValues);

				// Call the overload that takes an array of SqlParameters
				return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName, commandParameters);
			}
			else 
			{
				// Otherwise we can just call the SP without params
				return ExecuteNonQuery(connectionString, CommandType.StoredProcedure, spName);
			}
		}

		/// <summary>
		/// Execute a SqlCommand (that returns no resultset and takes no parameters) against the provided SqlConnection. 
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders");
		/// </remarks>
		/// <param name="connection">A valid SqlConnection</param>
		/// <param name="commandType">The CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">The stored procedure name or T-SQL command</param>
		/// <returns>An int representing the number of rows affected by the command</returns>
		public static int ExecuteNonQuery(SqlConnection connection, CommandType commandType, string commandText)
		{
			// Pass through the call providing null for the set of SqlParameters
			return ExecuteNonQuery(connection, commandType, commandText, (SqlParameter[])null);
		}

		/// <summary>
		/// Execute a SqlCommand (that returns no resultset) against the specified SqlConnection 
		/// using the provided parameters.
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>