Variable to be Accessed throughout code [modified] - C# Discussion Boards

12-Feb-11 16:37

Hi All,

I would like to assign a value to a variable in the Default.aspx.cs section of my code. This value will never change. To prevent having to capture this value throughout the code I want this variable to be accessable throughout the Web Application.

The code looks like this:

public partial Class _Default : System.Web.UI.Page
{
    public static int timeout;    //variable to access

    protected void Page_Load(object sender, EventArgs e)
    {
        //...Get timeout from web.config file here
        timeout = toVal;
    }
}

One of the classes I want to access the static "timeout" variable:

public partial class FormPage : System.Web.UI.Page
{
    protected void Page_PreInit(object sender, EventArgs e)
    {

       // How do I access timeout variable here?
    }
}

I had another idea to make a seperate class file out of the code that gets the timeout value from the web.config file. Each time the timeout value is needed call the class and return the timeout. I just feel this would be a waste being that the timeout value will always be the same.

Any help would be really appreciated.
I'm also open to suggestions.
Thank you

modified on Saturday, February 12, 2011 10:51 PM

OriginalGriff12-Feb-11 21:21

OriginalGriff

12-Feb-11 21:21

Put it in the web.config file or in a session variable.

Static variables are for the life of the class, not globally applied - they will be removed when the instance of the application terminates.

When does the app terminate? For ASP.NET, it terminates when the page load is finished.

I.e. The page request arrives at the server. The app is started, returns the page and is terminated. Any postback, or new page request starts a new instance of the app.

Putting it in a static variable won't work: the static variable would have to be set up anew every time the page is loaded!

MWRivera13-Feb-11 4:07

13-Feb-11 4:07

Thank you for your reply.
The timeout is stored in the web.config file, this is where the value is being retrieved from. I need to use this value in my code on multiple pages within the web application.

I am trying to add the value to a session variable within the default.aspx.cs file and then trying to retrieve it from the session variable in another but keep getting the error:

"Object reference not set to an instance of an object."

This indicates to me that the session variable is null, but how can this be when I previously populated it in the default page?

Here is some basic code I put together to make it simpler for testing:

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Session.Add("Test", "Testing session pass");
    }
}

public partial class FormPage : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {        
        Response.Write(Session["Test"].ToString());            //<-- Get error on this line
    }
}

Do you know what the problem is?

Thank you

OriginalGriff13-Feb-11 5:42

OriginalGriff

13-Feb-11 5:42

I just tried it locally to be on the safe side, and the only way I could duplicate your problem was by closing the browser and starting a new run, but going directly to a page rather than via the default page. Are you sure you loaded the default page first?

MWRivera14-Feb-11 15:31

14-Feb-11 15:31

Thank you. That was the problem, I wasn't running the code from the default.aspx file when testing it out of VS.
Thank you for taking the time to help me out with this. I appreciate it.

RichardGrimmer15-Feb-11 3:55

RichardGrimmer

15-Feb-11 3:55

I understand that you don't want to "capture" this value, but isn't this an application setting? If so, add it to the web.config and access it using

ConfigurationManager.AppSettings["MySettingName"]

If it's a per-user setting, then put it into session (which is per-user) and access using

Session["MySettingName"]

.....App settings and Session are provided for precisely this kind of thing, so it seems a little redundant to "re-invent the wheel" to store it in another way....

Admittedly, both AppSettings and Session (and Application state for that matter) are dictionaries, so there is a small overhead in the lookups.

C# has already designed away most of the tedium of C++.

MWRivera15-Feb-11 4:03

15-Feb-11 4:03

Hi Richard,

Thank you for your reply. The timeout value is stored in the web.config file and after reviving OrigionalGriff's post I went and stored the value, taken from the web.config file and stored it in a session variable.
It appears to be the same solution you propose, which I'm happy to hear as it seems to be the best way to go about it.

Thank you again,
Mel

Simple calculator

nstk12-Feb-11 7:28

12-Feb-11 7:28

Hallo everyone,

I want to make a Simple calculator, as an exercise to get familiar with GUI and C#

I can easily drag 10 buttons, name them btn1, btn2... btn0 and then create the appropriate functions like

private void btn1_Click(object sender, EventArgs e)

and let a member variable have the appropriate value.

But...

isn't there a better way to deal with that? Something like having an array[9], where every field is a button, or sort of it?

I find it ugly and really annoying having 10 functions who do quite the same thing.

Thanks...

Luc Pattyn12-Feb-11 7:37

12-Feb-11 7:37

several Controls can share some handler, and Controls have a nice Tag property where you can store whatever you like. So it could be:

AnyDigitButton_Clicked(object sender, EventArgs e) {
    Button btn=sender as Button;
    number=10*number+(int)btn.Tag;
}

PS: there are lots of articles on calculators around, search CodeProject or Google, and see how they do it.

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

nstk12-Feb-11 11:07

12-Feb-11 11:07

Thanks for replying.

And how do you link all buttons in a handler? Maybe by putting them inside a groupBox? I tried it so but didn't work. Where does the Method 'AnyDigitButton_Clicked' come from?

Manfred Rudolf Bihy12-Feb-11 11:19

Manfred Rudolf Bihy

12-Feb-11 11:19

You add a handler to each of the buttons click event, but that handler can be created from the same function. That's it.

Luc Pattyn12-Feb-11 11:21

12-Feb-11 11:21

The details depend on the IDE you use. How do you usually tell your app to execute some event handler when some event occurs? you normally can choose the handler's name, choosing a pre-existing one should also be possible.

nstk wrote:
Maybe by putting them inside a groupBox?

Nope. GroupBoxes do have their use, especially with RadioButtons, here they most likely don't.

nstk wrote:
Where does the Method 'AnyDigitButton_Clicked' come from?

I wrote it; it should show you all it takes is just a few lines of code.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

nstk13-Feb-11 23:57

Re: Simple calculator [modified]

13-Feb-11 23:57

I did the above by adding the 'AnyDigitButton_Clicked' as a handler to the Click Event, but I get the following error:

When casting from a number, the value must be a number less than infinity
Frown | :(

A declaration of number as

int number = 0;

inside or outside the function didn't change anything...

nstk14-Feb-11 3:52

14-Feb-11 3:52

I think I found the solution, being

number = Convert.ToInt32(btn.Tag);

modified on Monday, February 14, 2011 10:08 AM

DaveyM6912-Feb-11 12:22

DaveyM69

12-Feb-11 12:22

If you're using Visual Studio, select the button then in the Properties window click the events icon.
In the dropdown next to the event (Click in this case) you can select any method with the correct signature. Selecting the same method for all button's click event will result in the same handler being called.

To get the value, as Luc said you can use the Tag property - although I would be tempted to add a more suitable property such as Value which would hold an int... something like this:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;

public class CalculatorDigitButton : Button
{
    public const int MaxValue = 9;
    public const int MinValue = 0;

    public CalculatorDigitButton()
    {
        base.Text = "0";
    }

    private int value;

    [Browsable(false)]
    public new string Text
    {
        get { return base.Text; }
        set { }
    }
    public int Value
    {
        get { return value; }
        set
        {
            if (value < MinValue || value > MaxValue)
                throw new ArgumentOutOfRangeException(
                    "value",
                    string.Format("Value must be between {0} and {1}",
                        MinValue, MaxValue));
            this.value = value;
            base.Text = value.ToString();
        }
    }
}

public enum CalculatorFunction
{
    Add,
    Subtract,
    Multiply,
    Divide
}

public class CalculatorFunctionButton : Button
{
    private static readonly List<string> FunctionText = new List<string>(4){
        "+", "-", "*", "/" };

    private CalculatorFunction function;

    public CalculatorFunctionButton()
    {
        base.Text = FunctionText[0];
    }

    public CalculatorFunction Function
    {
        get { return function; }
        set
        {
            if (!Enum.IsDefined(typeof(CalculatorFunction), value))
                throw new ArgumentException(
                    "Function must be a defined value", "Function");
            function = value;
            base.Text = FunctionText[(int)function];
        }
    }
    [Browsable(false)]
    public new string Text
    {
        get { return base.Text; }
        set { }
    }
}

Your event handlers for these may look something like this:

// Assign each digit button's click event to this handler
private void CalculatorDigitButtonClick(object sender, EventArgs e)
{
    CalculatorDigitButton calculatorDigitButton = sender as CalculatorDigitButton;
    if (calculatorDigitButton != null)
    {
        // Do your thing, value is in calculatorDigitButton.Value
    }
}
// Assign each function button's click event to this handler
private void CalculatorFunctionButtonClick(object sender, EventArgs e)
{
    CalculatorFunctionButton calculatorFunctionButton = sender as CalculatorFunctionButton;
    if (calculatorFunctionButton != null)
    {
        // Do your thing, function is in calculatorFunctionButton.Function
    }
}

Dave

Binging is like googling, it just feels dirtier.
Please take your VB.NET out of our nice case sensitive forum.
Astonish us. Be exceptional. (Pete O'Hanlon)

BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

Luc Pattyn12-Feb-11 18:04

12-Feb-11 18:04

That's a lot of code to avoid an (int) cast, as that is what the specialized button class is basically doing.

And I just realized, the digit buttons probably have a simple numeric Text property already, so maybe int.Parse(btn.Text) is the better approach. Keep in mind it will execute less than once per second as it is an input part of the GUI.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

DaveyM6913-Feb-11 2:48

DaveyM69

13-Feb-11 2:48

You're right of course, but I always try to take the approach, if it's a value it should be stored as a value. If I want to display a string representation, then I do it by calling ToString or whatever on the value.

Using the Text property as the value by calling Parse would just bug me!
Using Tag would be preferable to that as it's just simple boxing/unboxing, but when subclassing is so easy and the auto Text mechanism (plus any other functionality required) can then be built in, that's the way I would go.

Luc Pattyn13-Feb-11 3:01