Problems with an Indexer using a class as the type.

Bill, in the first line of SetVars_Click did you remember to remove the initial 'Hv' ?

Hv hv = new Hv();  // original

hv = new Hv(); // should now be

If you didn't, then a new local variable will still be created which will hide the field and so the latter will still be null when you try to access it in the other method.

Alan, the private Hv hv = null; didn't work.  Should the instances of the new Hv and V2 be defined outside of the two routines that will use them?

When executing the "if" statement you added in ReadVars_Click, it cause the same exception I had before, so hv is not visible in that routine.  The get and set both work in the first routine.

To enable your 'hv' variable to be accessible to all methods in the class, you need to make it into a private field rather than a local variable:

private Hv hv = null ; // now private field, initial value null

public void SetVars_Click(object sender, EventArgs e) {

hv = new Hv();

hv[0] = new V2();

hv[0].TS = "Test";

hv[0].TI = 1;

}

public void ReadVars_Click(object sender, EventArgs e) {

if (hv[0] != null) { // make sure not null

       Var1.Text = hv[0].TS; // hv and its indexer now accessible from ReadVars_Click

       Var2.Text = Convert.ToString(hv[0].TI);

}

}

Alan, that fixed the problem.  That really helped, thanks.  I can now set and get values in the single SetVars_Click routine. 

How would I now increase the scope so that values set in the SetVars_Click routine can be read in a similar ReadVars_Click routine?  The two routines are now as below these loose the contents because of the second instance in the second routine.  I have tried to make them static, with no luck.

public void SetVars_Click(object sender, EventArgs e) {

Hv hv = new Hv();

hv[0] = new V2();

hv[0].TS = "Test";

hv[0].TI = 1;

}

public void ReadVars_Click(object sender, EventArgs e) {

Hv hv = new Hv();

hv[0] = new V2();

Var1.Text = hv[0].TS;

Var2.Text = Convert.ToString(hv[0].TI);

}

Actually, Dave, I think the problem here is that hv[0] is null because, whilst Bill has initialized the hvv array, he hasn't assigned any V2 objects to its elements and so they are all null.

This should fix it:

Hv hv = new Hv();

hv[0] = new V2();

hv[0].TS = "Test";

Try changing it to:

         hv.hvv[0].TS = "Test";