Michael Colon Portfolio

Library Phase II – Windows Business & Data Access TiersIntroduction:For this project, I was responsible for developing the Windows Forms, Business Layer, and Data Access Layer for this n-tier library application. The Data Access tier utilizes stored T-SQL procedures to query and update SQL Server database tables. Within each stored procedure, I implemented data validation and proper error handling techniques. Created a custom exceptions class to catch Sql Exceptions and give the user a more detailed message, while avoiding an Exception error. The business tier acts as a middle tier between the Windows Application tier and the Data Access tier, passing data as objects to separate Data Access from Presentation Layer completely and ensuring that no SQL Code is in the application to prevent SQL Injection Attacks.Audience:This project is designed for library personnel to carry out typical library functions, such as adding members and checking in/out library books. The forms were designed to be easy to use, adhering to windows forms best-practices and multiple document interface usage. Project Goals:Design the Presentation, Business and Data Access tiers.Develop code that is scalable and easily maintainable.Provide adequate error handling.Use database-programming techniques that provide maximum programming flexibility and control while minimizing resource utilization. Use of ADO.NET for Utilizing SQL Stored ProceduresGet Members/// ,[object Object], /// ,[object Object],The member's member number (ID). /// ,[object Object], public Member GetMember(short memberNumber) { Member member = null; //Establish the connection using (SqlConnection con = new SqlConnection(MC.DataAccess.Properties.Settings.Default.LibraryConnectionString)) { //Instantiate a command with the connection for stored procedure //dbo.Adult_Member_Sel using (SqlCommand cmd = new SqlCommand(
dbo.Member_Sel
, con)) { cmd.CommandType = CommandType.StoredProcedure; #region Add Parameters cmd.Parameters.AddWithValue(
@member_no
, memberNumber); SqlParameter param = new SqlParameter(
@lastname
, SqlDbType.VarChar, 15); param.Direction = ParameterDirection.Output; cmd.Parameters.Add(param); param = new SqlParameter(
@firstname
@middleinitial
, SqlDbType.Char, 1); param.Direction = ParameterDirection.Output; cmd.Parameters.Add(param); param = new SqlParameter(
@street
@city
@state
, SqlDbType.VarChar, 2); param.Direction = ParameterDirection.Output; cmd.Parameters.Add(param); Continued on next page… Get Members Continued… param = new SqlParameter(
@zip
@phone_no
@expr_date
, SqlDbType.DateTime, 8); param.Direction = ParameterDirection.Output; cmd.Parameters.Add(param); param = new SqlParameter(
@is_juvenile
, SqlDbType.Bit, 1); param.Direction = ParameterDirection.Output; cmd.Parameters.Add(param); param = new SqlParameter(
@adult_member_no
, SqlDbType.SmallInt, 2); param.Direction = ParameterDirection.Output; cmd.Parameters.Add(param); param = new SqlParameter(
@birth_date
, SqlDbType.DateTime, 8); param.Direction = ParameterDirection.Output; cmd.Parameters.Add(param); #endregion try { //Open our connection and execute our query con.Open(); int returnValue = cmd.ExecuteNonQuery(); //Check to see if we have a juvenile if ((bool)cmd.Parameters[
@is_juvenile
].Value) { JuvenileMember jm = new JuvenileMember(); //Fill member properties jm.MemberID = (short)cmd.Parameters[
@member_no
].Value; jm.LastName = cmd.Parameters[
@lastname
].Value.ToString(); jm.FirstName = cmd.Parameters[
@firstname
].Value.ToString(); jm.MiddleInitial = cmd.Parameters[
@middleinitial
].Value.ToString(); jm.Street = cmd.Parameters[
@street
].Value.ToString(); jm.City = cmd.Parameters[
@city
].Value.ToString(); jm.State = cmd.Parameters[
@state
].Value.ToString(); jm.ZipCode = cmd.Parameters[
@zip
].Value.ToString(); jm.PhoneNumber = cmd.Parameters[
@phone_no
].Value.ToString(); jm.ExpirationDate = Convert.ToDateTime(cmd.Parameters[
@expr_date
].Value); jm.AdultMemberID = (short)cmd.Parameters[
@adult_member_no
].Value;Continued on next page… Get Members Continued…jm.BirthDate = Convert.ToDateTime(cmd.Parameters[
@birth_date
].Value); //Cast the juvenile member to a member member = (Member)jm; } else { member = new Member(); //Fill member properties member.MemberID = (short)cmd.Parameters[
@member_no
].Value; member.LastName = cmd.Parameters[
@lastname
].Value.ToString(); member.FirstName = cmd.Parameters[
@firstname
].Value.ToString(); member.MiddleInitial = cmd.Parameters[
@middleinitial
].Value.ToString(); member.Street = cmd.Parameters[
@street
].Value.ToString(); member.City = cmd.Parameters[
@city
].Value.ToString(); member.State = cmd.Parameters[
@state
].Value.ToString(); member.ZipCode = cmd.Parameters[
@zip
].Value.ToString(); member.PhoneNumber = cmd.Parameters[
@phone_no
].Value.ToString(); member.ExpirationDate = Convert.ToDateTime(cmd.Parameters[
@expr_date
].Value.ToString()); } } catch (SqlException sqlex) { switch (sqlex.State) { case 2: throw new LibraryException(ErrorCode.NoSuchMember); break; default: throw new LibraryException(ErrorCode.GenericException, sqlex.Message); break; } } catch (Exception ex) { throw new LibraryException(ErrorCode.GenericException, ex.Message); } } } return member; } #endregion }}This method is located in the Data Access class, which handles all calls to the database by use of stored procedures. The SQLCommand object is populated with input and output parameters, as well as calling a Custom Exceptions class. The catch blocks handle any SQLExceptions and throw a new custom Library Exception back to the presentation layer. Custom Exception Handlingpublic class LibraryException : Exception { private ErrorCode libraryErrorCode; public ErrorCode LibraryErrorCode { get { return libraryErrorCode; } } /// ,[object Object], /// ,[object Object], public LibraryException(string msg) : base(msg) { libraryErrorCode = ErrorCode.None; } /// ,[object Object], /// ,[object Object],The error code that indicates the reason for the exception. public LibraryException(ErrorCode errorCode) { libraryErrorCode = errorCode; } /// ,[object Object], /// ,[object Object],The error code that indicates the reason for the exception. /// ,[object Object],The error message that explains the reason for the exception. public LibraryException(ErrorCode errorCode, string msg) : base(msg) { libraryErrorCode = errorCode; } #endregion }This is a partial representation of a custom exceptions class I created for catching SQL Exceptions and rethrowing the exception as a Library Exception with a more detailed error message from the ErrorCode enumeration. Custom Exception Handlingpublic class ExceptionMessages { /// ,[object Object], /// ,[object Object],Library Exception /// ,[object Object], public static string HandleExceptions(LibraryException le) { string s; switch (le.LibraryErrorCode) { case ErrorCode.AddAdultFailed: s =
Add Adult Failed.
; break; case ErrorCode.AddJuvenileFailed: s =
Add Juvenile Failed.
; break; case ErrorCode.CheckInFailed: s =
Check In Failed.
; break; case ErrorCode.CheckOutFailed: s =
Check Out Failed.
; break; case ErrorCode.GenericException: s = le.Message; break; case ErrorCode.ItemAlreadyOnLoan: s =
Item is Already On Loan.
; break; case ErrorCode.ItemNotFound: s =
The Item was Not Found.
; break; case ErrorCode.ItemNotOnLoan: s =
The Item is Not Currently On Loan.
; break; case ErrorCode.MissingAdultMember: s =
Missing Adult Member.
; break; case ErrorCode.NoSuchMember: s =
Member not found.
; break; case ErrorCode.None: s =
No Error.
; break; default: s =
Exception Occurred.
; break; } return s; } } SQL Stored ProcedureCreate a Stored ProcedureCREATE PROCEDURE [dbo].[Member_Sel] -- Add the parameters for the stored procedure here@member_no SMALLINT = NULL,@lastname VARCHAR(15) = NULL OUTPUT, @firstname VARCHAR(15) = NULL OUTPUT, @middleinitial CHAR(1) = NULL OUTPUT,@street VARCHAR(15) = NULL OUTPUT,@city VARCHAR(15) = NULL OUTPUT,@state CHAR(2) = NULL OUTPUT,@zip CHAR(10) = NULL OUTPUT,@phone_no CHAR(13) = NULL OUTPUT,@expr_date DATETIME = NULL OUTPUT,@is_juvenile BIT = 0 OUTPUT,@adult_member_no SMALLINT = NULL OUTPUT,@birth_date DATETIME = NULL OUTPUTASBEGIN-- SET NOCOUNT ON added to prevent extra result sets from-- interfering with SELECT statements.SET NOCOUNT ON;--Check for nullsIF (@member_no IS NULL) OR (@member_no < 1) OR (@member_no > 32767)BEGINRAISERROR('Member ID is not valid.', 11, 1);RETURNEND--Check to see if member_no is in the juvenile tableIF (SELECT COUNT(*) FROM Juvenile WHERE member_no = @member_no) > 0BEGIN --Juvenile functionalitySET @is_juvenile = 1--Get juvenile informationSELECT @lastname = m.lastname, @firstname = m.firstname, @middleinitial = m.middleinitial,@birth_date = birth_date, @adult_member_no = adult_member_noFROM Juvenile AS jJOIN Member as mON j.member_no = @member_no AND m.member_no = @member_no--Get parent's information from @adult_member_noSELECT @street = street, @city = city, @state = state, @zip = zip, @expr_date = expr_date,@phone_no = phone_noFROM Adult WHERE member_no = @adult_member_noEND Stored Procedure Continued…ELSE IF (SELECT COUNT(*) FROM Adult WHERE member_no = @member_no) > 0BEGIN --Adult functionalitySET @is_juvenile = 0--Get adult informationSELECT @lastname = m.lastname, @firstname = m.firstname, @middleinitial = m.middleinitial,@street = a.street, @city = a.city, @state = a.state, @zip = a.zip, @expr_date = a.expr_date,@phone_no = a.phone_noFROM Adult AS a JOIN Member AS mON a.member_no = @member_no AND m.member_no = @member_noENDELSE BEGIN --Member does not exist errorRAISERROR('Member does not exist.', 11, 2);The following stored procedure is being called by an ADO.NET SqlCommand object. The stored proc returns all info into output parameters from either the Juvenile or Adult Table. If an error occurs, it raises it’s own SqlException with a specified State, which the Data Access Layer then bubbles up to the Presentation Layer for proper error handling and notification to the user. Business Layer public class BusinessLayer { /// ,[object Object], public BusinessLayer()… /// ,[object Object], /// ,[object Object],memberId to look up /// ,[object Object], public Member GetInformation(short memberId) { //Create a library data access object LibraryDataAccess lda = new LibraryDataAccess(); //Call the Get member method and pass in the memberId Member myMember = lda.GetMember(memberId); return myMember; } /// ,[object Object], /// ,[object Object],memberId /// ,[object Object], public ItemsDataSet GetBooks(short memberId) { //Create a library data access object LibraryDataAccess lda = new LibraryDataAccess(); //Call the GetItems method ItemsDataSet ids = lda.GetItems(memberId); return ids; } /// ,[object Object], /// ,[object Object],member who checked out book /// ,[object Object],ISBN of Book /// ,[object Object],copyNo of Book public void CheckOutBook(short memberId, int isbn, short copyNo) { //Create a library data access object LibraryDataAccess lda = new LibraryDataAccess(); //Call the CheckInItem Method lda.CheckOutItem(memberId, isbn, copyNo); } }The above class is partial and represents some of the methods within the business tier and communicates data between the presentation layer and the data access layer. Implementing Interfaces in Custom Classes [DeveloperInfo(
Mike Colon
, Date =
04/22/2009
, Title =
Products
)] [CustomDescription(
Products is a collection of Product: IList,[object Object]

Michael Colon Portfolio

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