BASIC OOP question

[cheezy]

Hi everyone;

 

I'm new at this and am pretty frustrated at what I'm missing here; hopefully somebody can enlighten me.

 

I have a class called DataStore that basically has a 2D Array in it:

 

public class DataStore  
{
public string[,] X;
public DataStore()
{
     InitializeString();
}
public void InitializeString()
{
 
}
public void StringMaker()
{
   string[,] X = new string[2,2];
               }
}

And I have a class Form1 (actually a Windows Form) that creates an instance of DataStore (called DS1):

public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Label label1;
public DataStore DS1;
private System.Windows.Forms.Button button1;
private System.ComponentModel.Container components = null;

public Form1()
{					InitializeComponent();
}

protected override void Dispose( bool disposing )
{
	if( disposing )
	{
		if (components != null) 
		{
		   components.Dispose();
		}
	}
	base.Dispose( disposing );
}


			
[sTAThread]
static void Main() 
{			
                               Form1 main_form = new Form1();
	main_form.Show();
	Application.Run();

}

private void Form1_Load(object sender, System.EventArgs e)
{
	DataStore DS1 = new DataStore();
 }

private void button1_Click(object sender, System.EventArgs e)
{
		
if (DS1  ==  null)
{
	MessageBox.Show("X is null already");
                         	}
else
{
	if(DS1.X == null)
	{
	               DS1.StringMaker();
		DS1.X[0,0] = "Foo";
		label1.Text = DS1.X[0,0].ToString();
	}
}

private void button2_Click(object sender, System.EventArgs e)
{
	 DataStore DS1 = new DataStore();
}
 }

 

 

Button 1 basically checks the 'health' of the object DS1.

 

The first time I click button1, DS1 is confirmed to be null, but I instantiated it on Form1 load. Button2 is just being ornery on my part, but it STILL doesn't instantiate. And if I EVER attempt to put something in the DS1.X[] string, I get "Object reference not set to an instance of an object." (of course I do; DS1 doesn't exist!!!)

 

Can someone enlighten me here; I've been scratching my head on this type problem for a while now and I'm at wits' end.

 

Thanks!!

[edit]Added the [cs] [/cs] tags - Orb[/edit]

Edited July 30, 2003 by John

[PlausiblyDamp]

change your form load to

  private void Form1_Load(object sender, System.EventArgs e)
   {
       DS1 = new DataStore();
    }

and all should be well.

 

Your current form load is declaring and instantiating a new variable called DS1 rather than referencing the form level one.

 

if you want button2 to work the same change will be needed.

[cheezy]

OK, Thanks; that probably solved (hopefully) half of the problem; now I get an "Object reference not set to an instance of an object." issue on the line below "DS1.StringMaker();" statement in the button1 click event.

 

Why isn't my DataStore StringMaker method instantiating my string? Should it have to, since I already created an instance of DS1?

 

Thanks!

[PlausiblyDamp]

same thing really

change the StringMaker method to

 

public void StringMaker()
   {
    X = new string[2,2];
   }

[cheezy]

That did it. Thank you very much. Now I can proceed instead of spin wheels!

 

Thanks again!!