Need help with this GUI

Question

I keep getting error when I try to remove students , etc.

Vulpes · Answer

I've just been having a look at it and I'm not surprised you're having problems as there are some serious flaws in the PersistantData class which you're not allowed to alter! I've done the best I can with it but notice that if you try to expand the membership to more than 10 the program will error out because of an error in the RetreiveStudents() method. Another problem is that there's only 5 students in the initial database but the aforementioned method returns an array of 10 student objects, the last 5 being null. The nulls need to be removed to avoid various problems arising: namespace Student_Viewer { public partial class Form1 : Form { private PersistantData data = new PersistantData(); private int corn = 0; private List ready; public Form1() { InitializeComponent(); ready = new List (data.RetreiveStudents()); // remove nulls for (int i = ready.Count - 1; i >= 0; --i) { if (ready[i] == null) ready.RemoveAt(i); } if (ready.Count > 0) DisplayStudent(ready[0]); else DisplayStudent(null); } private void DisplayStudent(Student stu) { //shows a student if (stu != null) { textBox6.Text = stu.FirstName; textBox5.Text = stu.LastName; dateTimePicker2.Value = stu.DateOfBirth; textBox7.Text = stu.Age.ToString(); textBox4.Text = stu.IdNumber.ToString(); } else { textBox6.Text = ""; textBox5.Text = ""; dateTimePicker2.Value = new DateTime(1990, 1, 1); textBox7.Text = ""; textBox4.Text = ""; } } private void button1_Click(object sender, EventArgs e) { //adds student to storage Student temp = new Student(this.textBox1.Text, this.textBox2.Text, this.dateTimePicker1.Value, Convert.ToInt32(this.textBox3.Text)); data.AddStudent(temp); ready.Add(temp); corn = ready.Count - 1; // display the student just added DisplayStudent(ready[corn]); // clear Add fields for next add textBox1.Text = ""; textBox2.Text = ""; textBox3.Text = ""; dateTimePicker1.Value = new DateTime(1990, 1, 1); } private void button7_Click(object sender, EventArgs e) { //remove this student if (ready.Count == 0) return; data.RemoveStudent(ready[corn]); ready.RemoveAt(corn); // display the student before the one removed if there is one, otherwise display first student if (corn > 0) --corn; else corn = 0; if (ready.Count > 0) DisplayStudent(ready[corn]); else DisplayStudent(null); } private void button2_Click(object sender, EventArgs e) { //shows the next student if (ready.Count == 0) return; if (corn DisplayStudent(ready[++corn]); } private void button5_Click(object sender, EventArgs e) { //shows the prev student if (corn > 0) DisplayStudent(ready[--corn]); } private void button4_Click(object sender, EventArgs e) { //shows the first student if (ready.Count == 0) return; corn = 0; DisplayStudent(ready[corn]); } private void button3_Click(object sender, EventArgs e) { //shows the last student if (ready.Count == 0) return; corn = ready.Count - 1; DisplayStudent(ready[corn]); } private void button6_Click(object sender, EventArgs e) { //make it so the student can be changed if (ready.Count == 0) return; if (button6.Text == "Edit") { button6.Text = "Save"; textBox6.ReadOnly = false; textBox5.ReadOnly = false; textBox4.ReadOnly = false; textBox7.ReadOnly = false; dateTimePicker2.Enabled = true; } else { ready[corn].FirstName = textBox6.Text; ready[corn].LastName = textBox5.Text; data.EditStudent(ready[corn]); button6.Text = "Edit"; textBox6.ReadOnly = true; textBox5.ReadOnly = true; textBox4.ReadOnly = true; textBox7.ReadOnly = true; dateTimePicker2.Enabled = false; } } } }

Prime b · Answer

ah ok, will do , ty!

Vulpes · Answer

Visual Studio is not able to rename its eventhandlers automatically when you change the name of a control - you have to do this yourself. The easiest way to do this is to right click on the name of the eventhandler in the code window, select Refactor -> Rename, enter the new name of the handler in the textbox and OK it. This should change it everywhere it's used including the InitializeComponent method.

Prime b · Answer

Vulpes why the names of the events didn't change? for example in the form1 button1_click remained the same even after i changed the names in form?

Prime b · Answer

Oh yeah you did say that. Thank you Vulpes, for all that trouble you had to go through.

Vulpes · Answer

As I said in my previous post, you'll have to change the DateOfBirth property in the Student class to read/write (yeah, I know you're not supposed to change it), otherwise you're not going to be able to edit it: public DateTime DateOfBirth { get { return dateOfBirth; } set { dateOfBirth = value; } } It will then build OK but won't run properly as some code in form1.cs hasn't yet been updated in line with my previous post - button2_Click for instance. So, I'd go through each method in turn, in the light of the changed names, to make sure you've picked up all the changes as it's quite intricate. Incidentally, the lines I originally had - checking that there were actually some students remaining in the database before doing anything - are no longer needed as all the navigation buttons will be disabled in this event.

Prime b · Answer

Vulpes, I did it all, but I get a single error! I re-uploaded the file so its easier for you to see , i changed all the names http://www.4shared.com/rar/dUztIHti/Student_Viewer.html Once you open it , you will the error.

Prime b · Answer

Oh thank you Vulpes!

Vulpes · Answer

The tendency in .NET is not to use cryptic abbreviations but to write out words in full. So, I'd use viewStudentFirstName rather than viewStudFName. The following is a bit rushed (as it's almost time for bed here) but should answer most of your other questions. I've had to change the Student class so that DateOfBirth is now a read/write property rather than read only: namespace Student_Viewer { public partial class Form1 : Form { private PersistantData data = new PersistantData(); private int corn = 0; private List ready; public Form1() { InitializeComponent(); ready = new List (data.RetreiveStudents()); // remove nulls for (int i = ready.Count - 1; i >= 0; --i) { if (ready[i] == null) ready.RemoveAt(i); } if (ready.Count > 0) DisplayStudent(ready[0]); else { DisplayStudent(null); button6.Enabled = false; button7.Enabled = false; } button4.Enabled = false; button5.Enabled = false; if (ready.Count { button2.Enabled = false; button3.Enabled = false; } } private void DisplayStudent(Student stu) { //shows a student if (stu != null) { textBox6.Text = stu.FirstName; textBox5.Text = stu.LastName; dateTimePicker2.Value = stu.DateOfBirth; textBox7.Text = stu.Age.ToString(); textBox4.Text = stu.IdNumber.ToString(); } else { textBox6.Text = ""; textBox5.Text = ""; dateTimePicker2.Value = new DateTime(1990, 1, 1); textBox7.Text = ""; textBox4.Text = ""; } } private void button1_Click(object sender, EventArgs e) { button7.Enabled = false; if (textBox1.Text.Trim() == "" || textBox2.Text.Trim() == "" || textBox3.Text.Trim() == "") { MessageBox.Show("All fields need to be completed", "Add Student Error"); textBox1.Focus(); return; } int id = Convert.ToInt32(this.textBox3.Text); foreach (Student s in ready) { if (s.IdNumber == id) { MessageBox.Show("There is already a student with the same ID number", "Add Student Error"); textBox3.Focus(); return; } } //adds student to storage Student temp = new Student(this.textBox1.Text, this.textBox2.Text, this.dateTimePicker1.Value, Convert.ToInt32(this.textBox3.Text)); data.AddStudent(temp); ready.Add(temp); corn = ready.Count - 1; // display the student just added DisplayStudent(ready[corn]); // clear Add fields for next add button2.Enabled = false; button3.Enabled = false; if (ready.Count == 1) { button6.Enabled = true; button7.Enabled = true; } textBox1.Text = ""; textBox2.Text = ""; textBox3.Text = ""; dateTimePicker1.Value = new DateTime(1990, 1, 1); button7.Enabled = true; } private void button7_Click(object sender, EventArgs e) { //remove this student DialogResult dr = MessageBox.Show("Are you sure you want to remove this student?", "Remove Student Confirmation", MessageBoxButtons.YesNo); if (dr == DialogResult.No) return; data.RemoveStudent(ready[corn]); ready.RemoveAt(corn); // display the student before the one removed if there is one, otherwise display first student if (corn > 0) --corn; else corn = 0; if (ready.Count > 0) DisplayStudent(ready[corn]); else { DisplayStudent(null); button6.Enabled = false; button7.Enabled = false; } if (corn == 0) { button4.Enabled = false; button5.Enabled = false; } if (ready.Count { button2.Enabled = false; button3.Enabled = false; } } private void button2_Click(object sender, EventArgs e) { //shows the next student DisplayStudent(ready[++corn]); if (corn == 1) { button4.Enabled = true; button5.Enabled = true; } if (corn == ready.Count - 1) { button2.Enabled = false; button3.Enabled = false; } } private void button5_Click(object sender, EventArgs e) { //shows the prev student DisplayStudent(ready[--corn]); if (corn == 0) { button4.Enabled = false; button5.Enabled = false; } if (corn == ready.Count - 2) { button2.Enabled = true; button3.Enabled = true; } } private void button4_Click(object sender, EventArgs e) { //shows the first student if (corn == 0) return; corn = 0; DisplayStudent(ready[corn]); button4.Enabled = false; button5.Enabled = false; button2.Enabled = true; button3.Enabled = true; } private void button3_Click(object sender, EventArgs e) { //shows the last student if (corn == ready.Count - 1) return; corn = ready.Count - 1; DisplayStudent(ready[corn]); button2.Enabled = false; button3.Enabled = false; button4.Enabled = true; button5.Enabled = true; } private void button6_Click(object sender, EventArgs e) { //make it so the student can be changed if (button6.Text == "Edit") { button6.Text = "Save"; button4.Enabled = false; button5.Enabled = false; button2.Enabled = false; button3.Enabled = false; button7.Enabled = false; textBox6.ReadOnly = false; textBox5.ReadOnly = false; textBox4.ReadOnly = true; // don't allow ID to be changed textBox7.ReadOnly = false; dateTimePicker2.Enabled = true; } else { DialogResult dr = MessageBox.Show("Are you sure you want to save the changes?", "Edit Student Confirmation", MessageBoxButtons.YesNo); if (dr == DialogResult.Yes) { ready[corn].FirstName = textBox6.Text; ready[corn].LastName = textBox5.Text; ready[corn].DateOfBirth = dateTimePicker2.Value; data.EditStudent(ready[corn]); } button6.Text = "Edit"; button4.Enabled = true; button5.Enabled = true; button2.Enabled = true; button3.Enabled = true; button7.Enabled = true; textBox6.ReadOnly = true; textBox5.ReadOnly = true; textBox4.ReadOnly = true; textBox7.ReadOnly = true; dateTimePicker2.Enabled = false; } } } }

Prime b · Answer

~

Prime b · Answer

I am trying to rename all the objects in this GUI, and I am having trouble to figure out what would be the best most descriptive name. For example( you have to have GUI running) if you click View Students tab you will see First Name label, the textbox next to it named textbox1, well I renamed that textbox1 to viewStudFName. viewStud stands for the tab name and FName is first name, is it good ? or should i rename to to something different?

Prime b · Answer

Yeah, did you see the the 2nd link in my first post? My teacher is Java programmer, and also we just getting in to the Chapter called Using Classes and Objects, so pretty much the chapter about how to create classes , etc. We actually just begin to learn OOP

Vulpes · Answer

Just for the record, if you make the highlighted changes to the RetreiveStudents() method, then it should work properly: public Student[] RetreiveStudents() { Student[] list = new Student[10]; students.Clear(); // clear list FileStream inFile = new FileStream(FILE_NAME, FileMode.Open, FileAccess.Read); BinaryFormatter binFormatter = new BinaryFormatter(); int index = 0; while (inFile.Position { if (index >= list.Length) { list = Expand(list); // need to assign result back to list } list[index++] = (Student)binFormatter.Deserialize(inFile); students.Add(list[index - 1]); } inFile.Close(); return list; } It's a bit rich asking you to begin method names with a lower case letter when they all begin with capital letters in the PersistantData class. That's the recommended practice for .NET anyway - how many methods have you seen in the framework that begin with lower case letters?. What they're asking you to do is the Java naming standard.

Prime b · Answer

yeah... did you like variable names ?lol I'll have to go through all of them and rename it, also I have to rename all the objects in the form it self, since they are default names if i wont change it then my teacher will give me bad grade(maybe C). And this is my last semester in this college so I need to get all A's in all four classes that I am currently taking otherwise I wont be accepted to a four college due to my GPA being below the limit.... I had fun during few semesters in community college and it killed my GPA so now I am trying to fix all the mistakes I did..... Also the reason I am telling you all this is so you wont think I am stupid or something.. I am good student , just met wrong people at college and it cost me a lot.

Prime b · Answer

Vulpes, anyone?

Need help with this GUI

Answers (15)