Programming Forums > Application Development > C#

BstrucT · Jun 10th, 2008, 7:16 AM

Hi guys.

One of the biggest hick - ups for me was trying to access data between forms using getters and setters

I also had a bit of trouble with MessageBoxes and certain file streaming IO functions.

I wrote a little application last night so that if I forget about one of these little issues, I can just go back and look again.

It may also prove handy for some newcomers out there who would like to know more about these things, maybe it won't.
The coding is definetely not top-notch, and the design sux, but here it is.

Description:

Application gets user information for a membership of some sort.
It then istantiates that info to another form, where the user can save the data.
(file will be written to default Debug folder.)
The file can then be opened or deleted or edited and saved again.

Probably not be a very practical example of where to use this type of stuff, but all comments will be appreciated. (That includes negative feedback, as that creates room for improvement)

>BstrucT

xavier · Jun 10th, 2008, 8:38 AM

2 issues :

 csharp Syntax (Toggle Plain Text) 
public string _txtBoxAge2
        {
            set
            {
                lblAge.Text = value;
            }
        }
public string _txtBoxAge2
        {
            set
            {
                lblAge.Text = value;
            }
        }

Why do you name properties starting with a _ and a lower case letter. The norm is to start with an uppercase letter. - UpperCamelCase -

and the seccond :

 csharp Syntax (Toggle Plain Text) 
try
            {
                StreamWriter writeMember = new StreamWriter(
                    lblName.Text);
 
                //Specify strings needed to be written
                writeMember.WriteLine(lblName.Text);
                writeMember.WriteLine(lblAge.Text);
                writeMember.WriteLine(lblAddress.Text);
                writeMember.WriteLine(lblContact.Text);
                writeMember.WriteLine(lblMembership.Text);
 
                //Close the stream
                writeMember.Close(); //[b]if an error appears before this you are not disposing of the writer[/b]
            }
            catch
            {
                MessageBox.Show(
                    "Make sure all fields have been populated.",
                    "Error",
                    MessageBoxButtons.OK,
                    MessageBoxIcon.Warning);
            }
            [b]finally{
                    writeMember.Close(); // this should be here.
             } [/b]
try
            {
                StreamWriter writeMember = new StreamWriter(
                    lblName.Text);

                //Specify strings needed to be written
                writeMember.WriteLine(lblName.Text);
                writeMember.WriteLine(lblAge.Text);
                writeMember.WriteLine(lblAddress.Text);
                writeMember.WriteLine(lblContact.Text);
                writeMember.WriteLine(lblMembership.Text);

                //Close the stream
                writeMember.Close(); //[b]if an error appears before this you are not disposing of the writer[/b]
            }
            catch
            {
                MessageBox.Show(
                    "Make sure all fields have been populated.",
                    "Error",
                    MessageBoxButtons.OK,
                    MessageBoxIcon.Warning);
            }
            [b]finally{
                    writeMember.Close(); // this should be here.
             } [/b]

OpenLoop · Jun 10th, 2008, 11:34 AM

Issue #1 is not an issue, it's a preference.

xavier · Jun 10th, 2008, 1:30 PM

Actually it's more about convention. If most of the people use a certain style - it's best to use that style.

For example - when I look at something like : _someName - I instantly assume it's a private variable. And so will most of .net programmers.

lectricpharaoh · Jun 10th, 2008, 5:51 PM

Quote:

Originally Posted by xavier

Actually it's more about convention. If most of the people use a certain style - it's best to use that style.

For example - when I look at something like : _someName - I instantly assume it's a private variable. And so will most of .net programmers.

QFT. This is exactly what I do in my code, as a) it's completely unambiguous, and b) it's less typing (and less ugly) than the ubiquituous 'm_' prefix that some prepend.

BstrucT · Jun 11th, 2008, 12:36 AM

Thanks for the tip xavier, I had a feeling the "_" wasn't a good idea, but wasn't sure how to write it. Much appreciated.

Oh my, I didn't even know there had to be a finally{} after the exception.
So I understand that if the error is catched, the execution will jump to the finally{} statement? I see now that I am disposing of the writer incorrectly.

@lectricpharaoh:
I have to agree, looks kinda ugly and out of place.

hehe, will refrain from doing that again.

>BstrucT

xavier · Jun 11th, 2008, 4:59 AM

Quote:

Oh my, I didn't even know there had to be a finally{} after the exception.
So I understand that if the error is catched, the execution will jump to the finally{} statement? I see now that I am disposing of the writer incorrectly.

No

.
http://www.csharpfriends.com/Article...?articleID=128 here's an article .. you can go from there with help from google.

lectricpharaoh · Jun 13th, 2008, 3:27 AM

Quote:

Originally Posted by BstrucT

Oh my, I didn't even know there had to be a finally{} after the exception.
So I understand that if the error is catched, the execution will jump to the finally{} statement? I see now that I am disposing of the writer incorrectly.

Nope. A finally block is usually to do cleanup. For example, say you want to open a file, read something, and then close the file. Loading configuration data at program start is a good example. Now, you wrap the read operation in a try block in case there's an I/O error or something, but whether or not an exception gets thrown, you still want to close the file, so you put that in the finally block.

In other words, whenever you have code that grabs/allocates a resource, uses it, and then releases/deallocates that resource, you might want to use a finally statement. It depends on the situation, but this is the most common case.

As for your original problem, yeah, just use properties. We don't call them 'getters' and 'setters' in C# most of the time, though (that's a term from languages like C++ and Java that don't support properties, so you need a method to do this if you want to maintain proper OO data hiding). What you can do is have one or more status properties on your secondary form(s) that you can check to determine whether other properties are valid. If you're opening a 'modal' dialog box- this is one that must be closed before you can interact with the main form, and is invoked with the ShowDialog() method- you can use the method's return value to determine status.

As an example, take the OpenFileDialog class. You instantiate it, call the ShowDialog() method, and after it returns, you can check the result to determine if the user selected a file, or instead clicked 'cancel' or hit 'esc'. If the user did not cancel the dialog box, then you can check the FileName or FileNames property to determine what file(s) they want to open. Basically, the idea here is to ensure the 'data' property actually contains something valid. If you try to open the file when they didn't select one, you've got a problem, so check the status first. This holds true in dialog boxes you create too.

BstrucT · Jun 17th, 2008, 1:57 AM

Wow thanks man.

Quote:

What you can do is have one or more status properties on your secondary form(s) that you can check to determine whether other properties are valid. If you're opening a 'modal' dialog box- this is one that must be closed before you can interact with the main form, and is invoked with the ShowDialog() method- you can use the method's return value to determine status.

As an example, take the OpenFileDialog class. You instantiate it, call the ShowDialog() method, and after it returns, you can check the result to determine if the user selected a file, or instead clicked 'cancel' or hit 'esc'. If the user did not cancel the dialog box, then you can check the FileName or FileNames property to determine what file(s) they want to open.

This will help me alot, thanks for showing me, also I read up alot on Exeption handling this weekend and think I'va got it covered more or less.

Thanks for the good advice.

>BstrucT

Jun 10th, 2008, 8:38 AM	#2
xavier Professional Programmer Join Date: Oct 2004 Location: .ro Posts: 379 Rep Power: 4	Re: Data between Forms 2 issues : csharp Syntax (Toggle Plain Text) public string _txtBoxAge2 { set { lblAge.Text = value; } } public string _txtBoxAge2 { set { lblAge.Text = value; } } Why do you name properties starting with a _ and a lower case letter. The norm is to start with an uppercase letter. - UpperCamelCase - and the seccond : csharp Syntax (Toggle Plain Text) try { StreamWriter writeMember = new StreamWriter( lblName.Text); //Specify strings needed to be written writeMember.WriteLine(lblName.Text); writeMember.WriteLine(lblAge.Text); writeMember.WriteLine(lblAddress.Text); writeMember.WriteLine(lblContact.Text); writeMember.WriteLine(lblMembership.Text); //Close the stream writeMember.Close(); //[b]if an error appears before this you are not disposing of the writer[/b] } catch { MessageBox.Show( "Make sure all fields have been populated.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning); } [b]finally{ writeMember.Close(); // this should be here. } [/b] try { StreamWriter writeMember = new StreamWriter( lblName.Text); //Specify strings needed to be written writeMember.WriteLine(lblName.Text); writeMember.WriteLine(lblAge.Text); writeMember.WriteLine(lblAddress.Text); writeMember.WriteLine(lblContact.Text); writeMember.WriteLine(lblMembership.Text); //Close the stream writeMember.Close(); //[b]if an error appears before this you are not disposing of the writer[/b] } catch { MessageBox.Show( "Make sure all fields have been populated.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning); } [b]finally{ writeMember.Close(); // this should be here. } [/b] __________________ Don't take life too seriously, it's not permanent !

Jun 10th, 2008, 11:34 AM	#3
OpenLoop Expert Programmer Join Date: May 2005 Location: East Lansing, MI Posts: 663 Rep Power: 4	Re: Data between Forms Issue #1 is not an issue, it's a preference.

Jun 10th, 2008, 1:30 PM	#4
xavier Professional Programmer Join Date: Oct 2004 Location: .ro Posts: 379 Rep Power: 4	Re: Data between Forms Actually it's more about convention. If most of the people use a certain style - it's best to use that style. For example - when I look at something like : _someName - I instantly assume it's a private variable. And so will most of .net programmers. __________________ Don't take life too seriously, it's not permanent !

Jun 11th, 2008, 12:36 AM	#6
BstrucT Hobbyist Programmer Join Date: Dec 2007 Location: Durban, South-Africa Posts: 169 Rep Power: 1	Re: Data between Forms Thanks for the tip xavier, I had a feeling the "_" wasn't a good idea, but wasn't sure how to write it. Much appreciated. Oh my, I didn't even know there had to be a `finally{}` after the exception. So I understand that if the error is catched, the execution will jump to the `finally{}` statement? I see now that I am disposing of the writer incorrectly. @lectricpharaoh: I have to agree, looks kinda ugly and out of place. hehe, will refrain from doing that again. >BstrucT __________________ The more the human race tries to change everything, when not needed, the less will they be able to change themselves when they need to.

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Programming Forums > Application Development > C#

Data between Forms