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#1 Malcolmpordes  Icon User is offline

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The name 'InitVariables' does not exist in the current context

Posted 13 December 2010 - 10:09 AM

I'm a C# newbie. I'm getting this error in the section of code below:

namespace SSTW
{
    public partial class FormGameType : Form
    {
        public FormGameType()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            InitVariables.GameType = 1; //Regular game
 
        }
    }
}



The other relevant code snippets are:

namespace SSTW
{
    class InitVars
    {
        public int GameType{ get; set; }
    }
}

namespace SSTW
{
    public partial class Form1 : Form
    {

        public Form1()
        {
            InitializeComponent();
            InitVars InitVariables = new InitVars();


Any help would be appreciated.

MOD EDIT: When posting code...USE CODE TAGS!!!

:code:

This post has been edited by JackOfAllTrades: 13 December 2010 - 10:14 AM


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Replies To: The name 'InitVariables' does not exist in the current context

#2 JackOfAllTrades  Icon User is offline

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Re: The name 'InitVariables' does not exist in the current context

Posted 13 December 2010 - 10:18 AM

You've created an object of InitVars type called InitializeVars within the scope of the Form1 method. It is not visible outside of that function and "disappears" once you leave that function. If you want your other class to be able to access that variable, you probably want to create a constructor for the FormGameType class that takes an InitVars object as a parameter and pass the one you create in your Form1 class's constructor to it.
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#3 tlhIn`toq  Icon User is offline

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Re: The name 'InitVariables' does not exist in the current context

Posted 13 December 2010 - 01:32 PM

Short and easy understanding of "Scope":
The scope of an object is the object's lifespan. An introductory way of looking at is that an object's lifespan is the space between matching braces.

In your code:
namespace SSTW
{
    public partial class Form1 : Form
    {

        public Form1()
        { // <== Start of scope
            InitializeComponent();
            InitVars InitVariables = new InitVars(); // <-- Only exists within the constructor
        } // <== End of scope


InitVars was made between the braces that surround the Form1 constructor. So InitVars is alive only within Form1 constructor method. Nothing outside of those braces is aware of it. When the constructor method is done executing, anything made within goes 'out of scope' and will be disposed of.

If you were to move it up one level to be within the braces than surround all of the Form1 class, then it would be alive as long as Form1 is alive, and it would be visible to anything else within the Form1 braces.

namespace SSTW
{
    public partial class Form1 : Form
    { // <== Start of scope
        InitVars InitVariables = new InitVars(); // <-- Now exists within the entire class of Form1

        public Form1()
        { 
            InitializeComponent();
        }
     } // <== End of scope
}


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#4 tlhIn`toq  Icon User is offline

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Re: The name 'InitVariables' does not exist in the current context

Posted 13 December 2010 - 02:04 PM

So there seems to be at least two more threads about scope and why can't a variable in one method be seen by another.

Let me be coarse for a second and suggest two things:
Pay attention in your class. I'm sure that scope was covered.
Buy an intro to C# book.


I am going to guess that you are trying to teach yourself C# without much guidance, a decent book or without knowing where to look. Sometimes just knowing where to look can make all the difference. Google is your friend.
Search with either "C#" or "MSDN" as the first word: "MSDN Picturebox", "C# Custom Events", "MSDN timer" etc.

But honestly, just typing away and seeing what pops up in Intellisense is going to make your self-education take 20 years. You can learn by trying to reverse engineer the language through banging on the keyboard - or you can learn by doing the tutorials and following a good "How to learn C#" book.

May I suggest picking up a basic C# introductory book? It's not that people here don't want to be helpful, but there is a certain amount of basic learning work that one should really take upon themselves before asking for help. There are so many great "How do I build my first application" tutorials on the web... There are dozens of "Learn C# in 21 days", "My first C# program" books at your local book seller or even public library... Asking a forum, any forum, to hand-hold you through it is just redundant. In many ways it disrespects the people who have invested dozens of hours in the on-line tutorials and those that spent thousands of hours in authoring books.

Build a Program Now! in Visual C# by Microsoft Press, ISBN 0-7356-2542-5
is a terrific book that has you build a Windows Forms application, a WPF app, a database application, your own web browser.

C# Cookbooks
Are a great place to get good code, broken down by need, written by coding professionals. You can use the code as-is, but take the time to actually study it. These professionals write in a certain style for a reason developed by years of experience and heartache.

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.

The tutorials below walk through making an application including inheritance, custom events and custom controls.
Quick and easy custom events
Bulding an application - Part 1
Building an application - Part 2
Debugging tutorial
Working with environmental variables

Writing a text file is always one of the first things people want to do, in order to store data like high-scores, preferences and so on
Writing a text file tutorial.

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

Have you seen the MSDN Code Samples? They spent a lot of time creating samples and demos. It seems a shame to not use them.

  • Anonymous Delegates: Demonstrates the use of unnamed delegates to reduce application complexity.
  • Arrays: Shows how to use arrays.
  • Attributes: Shows how to create custom attribute classes, use them in code, and query them through reflection.
  • Collection Classes: Shows how to make non-generic collection classes that can be used with the foreach statement.
  • COM Interop Part I: Shows how to use C# to interoperate with COM objects.
  • COM Interop Part II: Shows how to a use a C# server together with a C++ COM client.
  • Commandline: Demonstrates simple command-line processing and array indexing.
  • Condiational Methods: Demonstrates conditional methods, which provide a powerful mechanism by which calls to methods can be included or omitted depending on whether a symbol is defined.
  • Delegates: Shows how delegates are declared, mapped to static and instance methods, and combined into multicast delegates.
  • Events: Shows how to declare, invoke, and configure events in C#.
  • Explicit Interface: Demonstrates how to explicitly implement interface members and how to access those members from interface instances.
  • Generics: Shows how to make generic collection classes that can be used with the foreach statement.
  • Hello World: A Hello World application.
  • Indexers Part I: Shows how C# classes can declare indexers to provide array-like access to objects.
  • Indexers Part II: Shows how to implement a class that uses indexed properties. Indexed properties enable you to use a class that represents an array-like collection.
  • Libraries: Shows how to use compiler options to create a DLL from multiple source files; also, how to use the library in other programs
  • Named and Optional (C# 4.0): Demonstrates Named and Optional parameters, an alternative to method overloads
  • Nullable: Demonstrates value types, such as double and bool, that can be set to null
  • Office Sample (C# 4.0): Demonstrates how Dynamic and COM Interop make it easy to call Microsoft Office in C# 4.0
  • OLEDB: Demonstrates how to use a Microsoft Access database from C# by creating a dataset and adding tables to it.
  • Operator Overloading: Shows how user-defined classes can overload operators
  • Partial Types: Demonstrates how classes and structures can be defined in multiple C# source-code files
  • PInvoke: Shows how to call exported DLL functions from C#
  • Properties: Shows how properties are declared and used; also demonstrates abstract properties
  • Python Sample (C# 4.0): Learn how to call a Python script by using the Dynamic feature in C# 4.0
  • Security: Discusses .NET Framework security and shows how to modify security permissions in C# by using permission classes and permission attributes
  • Simple Variance (C# 4.0): See how Covariance and Contravariance are supported in generic interfaces and delegates
  • Structs: Shows how to use structs in C#.
  • Threading: Demonstrates various thread activities such as creating and executing a thread, synchronizing threads, interacting between threads, and using a thread pool
  • Unsafe: Shows how to use unmanaged code (code that uses pointers) in C#
  • User Conversions: Shows how to define conversions to and from user-defined types
  • Versioning: Demonstrates versioning in C# by using the override and new keywords
  • XML Documents: Shows how to document code by using XML
  • Yield: Demonstrates how to use the yield keyword to filter items in a collection

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#5 Malcolmpordes  Icon User is offline

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Re: The name 'InitVariables' does not exist in the current context

Posted 13 December 2010 - 03:02 PM

Thanks, that makes sense.
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#6 Malcolmpordes  Icon User is offline

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Re: The name 'InitVariables' does not exist in the current context

Posted 13 December 2010 - 04:14 PM

Hi Jackofalltrades,

I did what you suggested, I still get the same error message, probably because the InitVariables object is only visible within the FormGameType constructor, and not the button1_Click method. Is that right?

How do I pass an object to button1_Click?

Also how do I return an object from button1_Click?

Thanks.
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#7 JackOfAllTrades  Icon User is offline

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Re: The name 'InitVariables' does not exist in the current context

Posted 13 December 2010 - 04:22 PM

Read this older post of mine, as it applies here as well. It really sounds like you need to read your book on how classes work.

As far as returning something from an event handler like button1_Click, you cannot return data from an event handler. You can, of course, set the value of a member variable of your class (hint, hint).
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