[Elliotd123]

Creating a windows forms application using .net 3.5. It communicates with a digital projector via a serial port. I created a Settings class to create objects that essentially keep track of the users proposed changes to the settings.

Here are the objects:

public partial class projectorForm : Form
    {

        private static string comPort = "COM1";
        private SerialPort sp = new SerialPort(comPort, 115200);

        public static Settings defaultSettings = new Settings();
        public static Settings proposedSettings = new Settings();
        public static Settings currentSettings = new Settings();
...
}

Each Settings object keeps track of various settings, such as brightness. If I change the value of brightness in the "proposedSettings" object, for some reason the "currentSettings" brightness value changes as well. This doesn't happen to the "defaultSettings" object.

        private void brightnessSlider_Scroll(object sender, EventArgs e)
        {
            brightnessAmount.Text = "" + brightnessSlider.Value;
            proposedSettings.brightness.value = brightnessSlider.Value; 
          //As soon as the previous line executes, both proposedSettings.brightness.value and currentSettings.brightness.value get changed.
        }

What is going on???

[tlhIn`toq]

Why are are making these instances static?

Have you done the same thing with the property inside your Settings class?

That would cause this type of behavior.

Static means there is only one value of that 'thing' shared across instances.

See FAQ #5 for debugging tutorials
See FAQ #6 for Serialization and use of properties.

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[Curtis Rutland]

It's because static means "shared", as in, there's only one copy of a static property across all instances of a class.

Don't use static unless you know you need it.

[Elliotd123]

Thanks for the reply, however I don't believe it's a problem with them being static. They are static because several other classes change their values. Here's my Settings class:

public class Settings
    {
        public Entry brightness;
        public Entry contrast;

        public Entry colorGainRed;
        public Entry colorGainGreen;
        public Entry colorGainBlue;

        public Entry colorOffsetRed;
        public Entry colorOffsetGreen;
        public Entry colorOffsetBlue;

        public Settings()
        {
            brightness = new Entry("BRT", 50);
            contrast = new Entry("CON", 47);

            colorGainRed = new Entry("RCG", 50);
            colorGainGreen = new Entry("GCG", 50);
            colorGainBlue = new Entry("BCG", 50);

            colorOffsetRed = new Entry("RCO", 50);
            colorOffsetGreen = new Entry("GCO", 50);
            colorOffsetBlue = new Entry("BCO", 50);
        }

    }
    public class Entry
    {
        public string code = "";
        public int value = 0;

        public Entry(string Code, int Value)
        {
            code = Code;
            value = Value;
        }
    }

So each instance should have its own set of properties. I *did* run a debug on it. See original post. That exact line is where both values change. That line does not call another method.

We could get into whether or not the properties should be public or private with getter/setter methods, which is how I realize it probably should be done, but I don't *think* that's causing the problem at the moment.

This post has been edited by Elliotd123: 01 August 2011 - 10:53 AM

[tlhIn`toq]

Elliotd123, on 01 August 2011 - 11:52 AM, said:

They are static because several other classes change their values.

That is in NO WAY a valid reason for them to be static, nor the right way to allow access to them from other classes.

The tutorials below walk through making an application including inheritance, custom events and custom controls, object serialization and more.
Bulding an application - Part 1
Building an application - Part 2
Quick and easy custom events
Separating data from GUI - PLUS - serializing the data to XML
Passing values between forms/classes

[Elliotd123]

Ok, they're not static anymore. Same problem. Instead of having them be static, I passed the Settings to the other classes as a parameter. No change in how the program works though.

This post has been edited by Elliotd123: 01 August 2011 - 11:38 AM

[tlhIn`toq]

I'm building a simple test project to confirm something. So bear with me.

But I'm going to guess that since you ahve several other classes reading and writting here that you have some loop you are unware of reacting to a change and setting the other values.

Back in a sec

[Elliotd123]

If that were the case, wouldn't the debugger step into said loop?

[Elliotd123]

Ok I may be getting somewhere here. It's probably because I don't understand how C# compares objects...I have a statement that goes:

proposedSettings = currentSettings;

I'm guessing that in C# this does weird things with the two. If I comment this out, the problem goes away, so I'm assuming that C# doesn't make a copy, and instead assigns the same memory address to both objects? If that were the case then after this statement they would be the same thing.

[tlhIn`toq]

Ya know how you can know something, yet doubt it anyway? I had one of those moments. I just had to make sure that your 3 static classes weren't in some way acting as one.

So I ran up a quick test app that makes a class, then makes 3 static instances just like you've done but simplified.

Spoiler

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace StaticTest
{
    public partial class Form1 : Form
    {
        private static One Yogi = new One {PortName = "One", PortValue = 1};
        private static One Bear = new One {PortName = "Two", PortValue = 2};
        private static One BooBoo = new One {PortName = "Three", PortValue = 3};

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            textBox1.Text = Yogi.PortName;
            textBox2.Text = Yogi.PortValue.ToString();
            UpdateOtherBoxes();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            Yogi.PortName = textBox1.Text;
            UpdateOtherBoxes();
        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {
            Yogi.PortValue = Convert.ToInt32(textBox2.Text);
            UpdateOtherBoxes();
        }

        void UpdateOtherBoxes()
        {
            textBox4.Text = Bear.PortName;
            textBox6.Text = BooBoo.PortName;

            textBox3.Text = Bear.PortValue.ToString();
            textBox5.Text = BooBoo.PortValue.ToString();
        }
    }

    public class One
    {
        public One()
        {
            
        }
        public string PortName
        {
            get; set;
        }
        public int PortValue
        {
            get; set;
        }
    }
}

When run this confirmed what we all knew: That the three static classes were indeed separate from each other and do not cause each other to interact. If they had, we would have seen the lower textboxes here change to match the values of the two upper ones. That didn't happen.



So I have to go back to my recent comment that your multiple classes are interacting in a way you didn't intend, and bouncing the new value into the other instances.

You should be able to see this happening if you put a breakpoint within the set method of a property then look at the call to see which methods were called to get to that point.

[tlhIn`toq]

Quote

Ok I may be getting somewhere here. It's probably because I don't understand how C# compares objects...I have a statement that goes:

proposedSettings = currentSettings;

I'm guessing that in C# this does weird things with the two. If I comment this out, the problem goes away, so I'm assuming that C# doesn't make a copy, and instead assigns the same memory address to both objects? If that were the case then after this statement they would be the same thing.

That's not a comparrison. You are setting the left hand object to be the right hand object. Nothing weird about this.

int a = 1;
string Yogi = "Bear";
Settings propsosedSettings = currentSettings;

This post has been edited by tlhIn`toq: 01 August 2011 - 12:10 PM

[Elliotd123]

Yeah that was the problem. Since I'm not a huge C# programmer (Although I like the language), I didn't realize that C# doesn't make a COPY of an object when you do that, it just sets them both to the same memory location. As a result, changing one will thereafter change the other one. I fixed this problem by creating a copy constructor in the Settings class, and then invoking that constructor when assigning the new settings.

proposedSettings = new Settings(currentSettings);

Now it works like a charm. Thanks guys. And thank you also for the advice on static modifiers.

[tlhIn`toq]

If you aren't sure how C# does these sorts of things then I can only assume C# is new to you. ??

Let me make the same suggestion I make 20 times a week here: Don't try to make a project from scratch for a useful purpose, as your learning project. You're still learning the language and syntax. You don't yet know enough to design and architect a solution if you don't understand how basics like classes and assignments work.

If you come from a different language then you should be able to easily breeze through a few introductory tutorials because you only need to learn the differences in the coding languages and not the entire concept behind them.

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Writing a text file tutorial.
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Intermediate:
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Quick and easy custom events
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Everyone:
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I urge you to work through the C# learning series here on DIC, and to work a self-teaching book from cover to cover before you even think about designing your own applications.


Microsoft Visual Studio Tips, 251 ways to improve your productivity, Microsoft press, ISBN 0-7356-2640-5
Has many, many great, real-world tips that I use all the time.

These are just good every-day references to put in your bookmarks.
MSDN C# Developers Center with tutorials
Welcome to Visual Studio
Free editions of Visual Studio 2010

Let me also throw in a couple tips:

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  btnSave(object sender, eventargs e)
  {
      SavePreferences();
  }
  
  SaveMenuItem(object sender, eventargs e)
  {
      SavePreferences();
  }
  
  SaveContextMenu(object sender, eventargs e)
  {
      SavePreferences();
  }
  
  FormMain_Closing(object sender, eventargs e)
  {
      if (IsDirty) SavePreferences();
  }
  

  
  
  
• This can't be stressed enough in today's world of cell phone messaging:
  Don't use txt/sms/leet/T9 speak like: u no, u r, dnt, wut i m do-n, coz, al gud, b4, ny1, and so on. like this guy:
  
  dis not b d'hood dawg... You are sitting at a real keyboard with a real monitor, not a cell phone. You are not here texting your high school posse to come to your kegger after their shift at Taco Bell. You are here asking for help from senior coding professionals who graciously donate their valuable time to helping the next generation of coders with their chosen craft. Please try to show them, yourself and the industry some respect by writing at least at an eighth grade level. (IE: English not ebonics or SMS, real words, punctuation and so on). If you can't take your own problem/question seriously enough to write like an adult, then why would you expect anyone else to take it seriously?
  
  
• I strongly suggest installing VMware or some other virtualization technology on your development PC so you can create a couple virtual computers for testing. This would allow you to debug and test inside: WinXP32, XP64, Vista, Win7x32, Win7x64... etc. without having to actually have 5 physical PC's. Visual Studio will let you send the debug directly into one of these virtual machines so you can watch it operate, check its variables, see the crashes and so on just as if it were debugging on your real machine.

[Sergio Tapia]

Good thread all around, make it rain karma in this one.

[tlhIn`toq]

Elliotd123, on 01 August 2011 - 01:11 PM, said:

Yeah that was the problem. Since I'm not a huge C# programmer (Although I like the language), I didn't realize that C# doesn't make a COPY of an object when you do that, it just sets them both to the same memory location. As a result, changing one will thereafter change the other one. I fixed this problem by creating a copy constructor in the Settings class, and then invoking that constructor when assigning the new settings.

proposedSettings = new Settings(currentSettings);

Now it works like a charm. Thanks guys. And thank you also for the advice on static modifiers.

Glad we could help. And welcome to C#. I hope to be seeing a lot more of you in this topic area. It's nice to see someone new that makes an effort and seems to have a grasp on it.

Don't forget, we're all volunteers. So if anyone in any question gives you helpful advice, that little green + is a great way to say "Thanks"