[RESOLVED] How to write a generic contact List to a file that's inside a List(of contacs)

[jumper77]

Hi everyone. I've been working on things with this type code for a little but, and I only just now wondered how to write out the generic list of contacts inside the List(of contacts). I hope that makes sense. Maybe it will when you see some code. I tried searching on the net, but it doesn't understand what I'm searching for.

So, here's the declarations.

Public newContact As New Contact()
Public contacts As New List(Of Contact)()

I've had a number of people look at my post, but no one has said anything. Maybe it's because I'm not being clear. Here's more code that will hopefully let you see what I am trying to do.

 With newContact
            .FirstName = firstName.Text
            .LastName = lastName.Text
            .PhoneNumber = PhoneNumber.Text
            .Birthday = Birthday.Value
            Using sw
                sw = AppendText(theFilename)
                sw.Write(.FirstName & "," & .LastName & "," & .PhoneNumber & "," & .Birthday)
                sw.WriteLine()
            End Using
        End With

So, newContact is a single class that contains the information associated with the class.
Contacts is a List of newContact that contains all information for all instances of newContact.

Disclaimer: I'm NEW at this stuff, so if the above explanation is not correct, I hope you know from the code what's going on cause.... I did my best guys...

I want to make sure my approach to getting the information is sound, and looks half way good <smile>

Since I can't get a search on the net to work, I will have to write my own code. Problem is, it would look like such a hack. It would work... just wouldn't want to show it to my friends. I'm pretty sure the logic will be centered around the Contacts count (with the "S" on the end of Contact)

I'm not exactly looking for someone to give me some pretty code. But if you can let me know a better way to search to find the answers or a link to some site, that would be great.

Thanks for any help. I do appreciate any help.

If you need more info, just ask.

edit: writing to a file is no problem... don't need help there <smile>

[jmcilhinney]

So, you're saying that you know how to write one Contact to a file but you want to know how to write all items in a List(Of Contact) to the file, correct? Just like walking is just taking one step multiple times, so writing a List(Of Contact) is just writing one Contact multiple times. You would write a For Each loop to enumerate the List and then, inside the loop, you would write the one current Contact to the file.

[jumper77]

Hi jmc, thanks from writing. I was thought that the "For each" loop would be the way to go. And I think that using "count" would be part of then loop as well.

Give me some time to wake up (coffee is still making) and I'll start looking at the code. Once I have something that seems to work, I'll post it to see what you think.

Thanks a bunch

[jmcilhinney]

And I think that using "count" would be part of then loop as well.

Nope. You just perform the desired action once For Each item in the list. The number of items is irrelevant. That only matters when using a For loop because that means getting items by index so you have to know what the upper bound of that index is.

[jumper77]

Ok, thanks for the information. Glad I don't have to use count. Makes it easier on me. I going to work on it some more and when I get something together I will post it and maybe you can tell if I'm doing it right or not.

thanks a bunch

[jumper77]

Starting to wake up a little... couple of dumb questions (I was never good a for loops). I'm thinking that the loop should be a nested loop. Is that true? Also, "count" of the outer loop seems to be stuck and does not increase to the next value.

The reason I say this is because I was watching in the debugger.

[Inferrd]

I can't think why you need nested loops for this. You really need to show the code you are using.

It should be as simple as:

Private Sub btnSave_Click(sender As System.Object, e As System.EventArgs) Handles btnSave.Click

    For Each someContact As Contact In contacts
        'Write the someContact.Info to file
    Next

End Sub

or similar.

[jumper77]

Hi inferred Nice to see you. Guess I'm making this harder than it should be. I took out the nested part and the code below is what I lave left. Do you think this will work?

        For Each person As Contact In contacts
            Write to file
        Next

thanks to everyone for putting up with my thick (or dumb) head

[Inferrd]

Should work. You're in the best position to know, though.....just try it

If it doesn't work as expected, post back with the code you are using, and say what is happening that shouldn't be happening.

[jumper77]

Here's the new code. And guess what? It works! yea!! I sure thought it would be harder than that. My problem is that even though I have used VB for a few years, I didn't know OOP. But I have some friends from here who are helping me get better at it. But because it seems to be more complicated to me, I don't expect solutions to be easy.

Anyway.. here's the new code.

        Dim writeFile As String = "tmpfile.txt"
        sw = AppendText(writeFile)
        For Each person As Contact In contacts
            Using sw
                sw.Write("Hello")
            End Using
        Next

Thank you Inferrd, and everyone who helped. You all took me to the answer without just handing me the code that was the solution. I like that. When you learn that way, you'll remember what you did more

[Inferrd]

[jumper77]

just found an Oops in the code. I kept getting one of my favorite errors for files. It's about not being able to do anything with the file because it was in use by another process. And as I'm sure you all know, the other process is us. I always managed to fix it, but never understood how or why.

I guess code first:

        Dim writeFile As String = "tmpfile.txt"
        'sw = AppendText(writeFile)
        For Each person As Contact In contacts
            Using sw
                sw = AppendText(writeFile)
                sw.WriteLine("Hello")
            End Using
        Next

You'll see that I have commented out the first "AppendText" line. This was the offending code. With that code being there, I had to close the file before I could write to it. Didn't make "any" sense to me. So I commented out that line and everything worked perfectly (before I was getting that exception). So if anyone reads this who is as dumb as me, this would be a good lesson. It really taught me a good one

thanks again everyone

[jmcilhinney]

Don't put the Using statement inside the loop. The whole point of a Using block is to dispose the object at the end of the block. Why would you want to dispose a StreamWriter every iteration of the loop? Think about it: open the file, loop through the list and write each item, close the file. The loop goes inside the Using block, not the other way around.

[jumper77]

I think you're right. When I first found "using" I thought it was really great. And I read where it took care of a lot of things like "flush" and "close", but as you said, doesn't make much sense in a loop. That would be the "start" of my issue about "is in use by another process". Let me rearrange my code, then I'll come back.

thanks a lot!

[jumper77]

That didn't take too long. here's the code

        Dim writeFile As String = "tmpfile.txt"
        sw = AppendText(writeFile)
        For Each person As Contact In contacts
            sw.WriteLine(firstName.Text & "," & lastName.Text & "," & PhoneNumber.Text & "," & Birthday.Value)
        Next
        sw.Flush()
        sw.Close()

I had to move the "AppendText" out of the loop because I started getting my favorite error again. Once I did that, everything's working great. I think I have it now. I think I have found all the gotcha's. I don't think I should put it in a try catch block, but not sure. What would you do?

[jumper77]

Update to my write to file section. There was a point that I wasn't getting. I changed textbox.filename to person.filename.
so here is that one line.

 sw.WriteLine(person.FirstName & "," & person.LastName & "," & person.PhoneNumber & "," & person.Birthday)

I think that is MUCH better than the ugly code I was doing before. Plus, it should work because I'm connecting directly to the object I need.

[jumper77]

If anyone is still listening to this thread... HELP!... I just now started paying attention to what was being written to the file inside the "for each" loop, and the behavior is odd. Let me explain:

When you enter the first name (record) you want to save, it writes it to the file once.
When you enter the second name you want to save, it writes it to the file twice.
And when you enter the third name you want to save, it writes it to the file three times.

And I'm sure that this would go on and on.

If makes me feel like I should be removing a contact after I write it to the file. I think that would do it, but I don't know it that's the right thing to do.

So if there is anyone out there listening (and you give a damn)<smile> let me know what you think.

thanks a bunch

edit: forgot code:

 For Each person As Contact In contacts
            sw.WriteLine(person.FirstName & "," & person.LastName & "," & person.PhoneNumber & "," & person.Birthday)
        Next

Another thing, person.count goes up every time you add a record. I'm guessing this has something to do with it???

[techgnome]

How did you open the file? Odds are, you're opening the file for appending... so when you save, the first time, there's only one element. Then you add a second... since you append to the file, it writes the first item again, followed by the second... and so on... try just opening the file for write, not append, and see if you get the results you're looking for.

-tg

[jumper77]

OOOOOOOOOOOOOHhhhhhhhhhhhhhh that just might be it. I've been doing append now for so long. give me a minute and I'll give it a try

thanks tg!

[jumper77]

Ok, I'm having a problem finding something quick. can you tell me what to use instead of append?

[techgnome]

Instead of AppendText, try CreateText

-tg

[jumper77]

CreateText sounds like it would overwrite the file, but I'll try it. be back in a sec

[jumper77]

Nope... I think it's the count going up. and OF COURSE count is read only.

*edit* CreateText works the same as append

[techgnome]

Don't know... the only other possibility is that what's in your list is in there multiple times...

-tg

[jumper77]

I "think" I might have found something. If I put my own count in the loop and only let go through once that would work. But that's not a good solution because it could cost you in a big project. Still looking into what I can do.

[techgnome]

Whaaaaa?

you should be doing the steps in this order:
1) open the file
2) for each contact in contactlist
3) write out the contact info
4) -next-
5) close file

that's it and nothing more... do you have a loop in a loop of some kind?

-tg

[jumper77]

tg, the reason I said that is because that the number of times a record is written to the file is always Contacts.Count
If count is 3, it writes the contact three times. And it just keeps going up as the count does.

I don't really understand. Someone either gave me the "for each" loop or showed me some pseudo code.

Here's the loop.

        For Each person As Contact In contacts
            sw.WriteLine(person.FirstName & "," & person.LastName & "," & person.PhoneNumber & "," & person.Birthday)
        Next

At the top of the file there's this.

    Public newContact As New Contact()
    Public contacts As New List(Of Contact)()

if you see anything wrong with all of this, PLEASE let me know. I can't figure it out.

[jmcilhinney]

tg, the reason I said that is because that the number of times a record is written to the file is always Contacts.Count
If count is 3, it writes the contact three times. And it just keeps going up as the count does.

I don't really understand. Someone either gave me the "for each" loop or showed me some pseudo code.

Here's the loop.

        For Each person As Contact In contacts
            sw.WriteLine(person.FirstName & "," & person.LastName & "," & person.PhoneNumber & "," & person.Birthday)
        Next

At the top of the file there's this.

    Public newContact As New Contact()
    Public contacts As New List(Of Contact)()

if you see anything wrong with all of this, PLEASE let me know. I can't figure it out.

You're adding the same Contact object to the List multiple times instead of adding multiple distinct Contact objects. Get rid of that 'newContact' field. When you want to create a new Contact, declare a local variable there and then and create the object with the New keyword there and then. If you only use New once then you only have one object.

[jumper77]

Sorry... had to go to the store:
That kind of makes my brain twizzle. So dim a local object and it will be added to the list. That way it won't interfere with the list as a whole. I'm going to try that right now and see how it works. Thanks. I believe that you have found what I was doing wrong. Will let you know in a few minutes..

[jmcilhinney]

So dim a local object and it will be added to the list.

No. There's no local object. Your poor terminology is indicative of the issue. You declare a local VARIABLE and then you create multiple OBJECTS and assign them each to that variable in turn. The distinction between an object and a variable is critical. A variable is a place to put an object. A single variable can only refer to one object at a time but it can refer to different objects at different times. A single object can be referred to by multiple variables at the same time. It's just like real life. I am just one person but I can be referred to in many ways, e.g. myself, my sister's brother, my father's son, etc. Each of those references can be considered a variable while I am the object.

Here's an example that demonstrates what you're currently doing:

Dim myThing As New Thing
Dim things As New List(Of Thing)
 
For i = 1 To 3
    myThing.Name = "Thing " & i
    things.Add(myThing)
Next
 
For Each theThing In things
    Console.WriteLine(theThing.Name)
Next

In that case, there is only one Thing object. That same object gets added to the List three times. The last value that was assigned to that Thing object's Name property is "Thing 3" so that is what will be output three times at the end. This demonstrates what you should be doing:

Dim myThing As Thing
Dim things As New List(Of Thing)
 
For i = 1 To 3
    myThing = New Thing
    myThing.Name = "Thing " & i
    things.Add(myThing)
Next
 
For Each theThing In things
    Console.WriteLine(theThing.Name)
Next

In that case, a new Thing object is created on each iteration of the first loop so three distinct Thing objects are added to the to the List. Each object has its Name set to a different value so you will see three different outputs at the end. That code could also, and should also, be written like this:

Dim things As New List(Of Thing)
 
For i = 1 To 3
    Dim myThing As New Thing
 
    myThing.Name = "Thing " & i
    things.Add(myThing)
Next
 
For Each theThing In things
    Console.WriteLine(theThing.Name)
Next

By declaring the 'myThing' variable at the narrowest scope possible, you ensure that you can't make the mistake of creating too few objects.

[jumper77]

Well... it didn't work, but I may have not understood you well (actually that's quite possible). Here's the whole sub so you can see it. I just now put the top "New" in there

    Private Sub addRecord()
        'msg.ShowMsg(Reflection.MethodBase.GetCurrentMethod().ToString)

        Dim newContact As New Contact()
        With newContact
            .FirstName = firstName.Text
            .LastName = lastName.Text
            .PhoneNumber = PhoneNumber.Text
            .Birthday = Birthday.Value
        End With
        contacts.Add(newContact)

        Dim sw As IO.StreamWriter
        sw = IO.File.AppendText("logfile.txt")
        Dim ex As Exception = Nothing
        sw.WriteLine(Reflection.MethodBase.GetCurrentMethod().ToString)
        sw.Flush() : sw.Close()

        Dim contactFile As String = "Contacts.txt"
        sw = IO.File.CreateText(contactFile)

        For Each person As Contact In contacts
            sw.WriteLine(person.FirstName & "," & person.LastName & "," & person.PhoneNumber & "," & person.Birthday)
        Next
        sw.Flush() : sw.Close()
        msg.ShowMsg(newContact.FirstName & " " & newContact.LastName & " Saved")
    End Sub

*edit* code hasn't been cleaned up so it has a lot of junk in there that I'm not using. mostly the exception part

[jumper77]

Hi jmc. good to hear from you. Just want to let you know that I believe you know the answer and I'm working on understanding it so I can apply it to my code. I'll talk more in just a bit. I'm sorry but I missed your post. I do wish I had noticed it sooner.

[jumper77]

jmc, back again. It's going to take me a bit to get this working because I have to learn the behavior of your code, and also learn how/where to apply it. Thank you so much. Your last post holds the key to solving this, I'm pretty sure. But won't know until tomorrow. Right now my blood pressure is too high

And it's normally 120/80

[jumper77]

YES!! The brain damage has subsided. I said I was going to leave it alone, but just couldn't. But the good news is.... It's now working. The answer came from 2 people helping where each other seemed to be filling me in on the parts the other person didn't mention. And it worked out great.

So thank you jmc and thank you inferrd for all your help. I cleaned up the code so I could post it, so here it is...

    Private Sub addRecord()

        Dim person As New Contact()
        Dim contacts As New List(Of Contact)()

        person.FirstName = firstName.Text
        person.LastName = lastName.Text
        person.PhoneNumber = PhoneNumber.Text
        person.Birthday = Birthday.Value
        contacts.Add(person)

        Dim contactFile As String = "Contacts.txt"
        sw = IO.File.AppendText(contactFile)

        For Each newPerson As Contact In contacts
            sw.WriteLine(newPerson.FirstName & "," & newPerson.LastName & "," & newPerson.PhoneNumber & "," & newPerson.Birthday)
        Next
        sw.Flush() : sw.Close()
        msg.ShowMsg(person.FirstName & " " & person.LastName & " Saved")
    End Sub

Now this code only goes through the "for each" function only once for each record. I know I'm thick headed and it takes a while to get something through my head, but when it does, I have more and more understanding of what's going on.

so thanks everyone. And I do mean EVERYONE

Good night all

[jumper77]

Not awake yet (4:30 AM), but I just thought of something. Now that the code is working and it only goes through the loop one time, I don't really need the loop. I should just be able to have the one writeline and that's it.

Going to try it and see what happens.

And good morning everyone. Hope you had a great night

[jumper77]

Yep, at least I was right about something. There is no need for a loop at all, now that only one record at a time is written to the file. Plus, now I can put into a "using" block. I love those things.

Now, something that needs to be said.... tg, I forgot to mention you for your part in helping me to understand. And everyone of you get a +1 for a rep

*edit* Oh, I forgot one other person. Thanks to inferrd for help. +1 for you as well

[jmcilhinney]

Oh, I forgot one other person. Thanks to inferrd for help. +1 for you as well

Hey! You thanked Inferrd in post #34 and now you've thanked them again. That's not fair. Now you have to thank the rest of us a second time too.

[jumper77]

Hey! You thanked Inferrd in post #34 and now you've thanked them again. That's not fair. Now you have to thank the rest of us a second time too.

Oh no!! Oops. Thank you again jmc and tg. Don't want to be unfair. All you have helped so much and I can't thank you enough.

[dbasnett]

Not awake yet (4:30 AM), but I just thought of something. Now that the code is working and it only goes through the loop one time, I don't really need the loop. I should just be able to have the one writeline and that's it.

Going to try it and see what happens.

And good morning everyone. Hope you had a great night

As long as you only have one contact that works. What if you have two?

[jumper77]

Hi db, I have tested it up to 4 contacts and it still works the same way.

*edit* I should have also said this: on the window where you enter the information. the information is not saved until you clicked the "save" button. So you are only allowed to enter a contact one at a time.