Function from .cs file calling function from a different .cs file

What I am trying to do (in brief terms):
I have a function in a .cs file (A) that needs to access a function in a different .cs file (B). Based on certain calculations, (B) will alter (A) variables.

The problem:
I keep getting the following WARNINGs:
warning CS0649: Field 'programX.MainWindow.tCodes' is never assigned to, and will always have its default value null
warning CS0649: Field 'programX.TriggerCodes.function_MainWindow' is never assigned to, and will always have its default value null

Possibly needed details:
OS: Windows 7 64-bit
Compiler: MS Visual Studio 2010 Ultimate
Language: C# (WPF)
Framework: 4.0

And finally, a sample piece of code:

In "MainWindow.xaml.cs":

Code:

---

namespace programX
{
        public partial class MainWindow : Window
        {
                public TriggerCodes tCodes;
               
                public MainWindow()
                {
                        InitializeComponent();
                }
               
                protected internal void doSomething()
                {
                        if (tCodes.triggerCodeFound("Hello World"))
                                return;
                       
                        Console.WriteLine("Didn't find it");
                }               
               
                public void sayHello(string message)
                {
                        StringBuilder msg = new StringBuilder();
                        msg.Append("Hello ");
                        msg.Append(message);
                       
                        // *should* write "Hello Silly Person!"
                        Console.WriteLine(msg.ToString());
                }
        }
}

---

In "TriggerCodes.cs":

Code:

---

namespace programX
{
        public partial class TriggerCodes
        {
                public MainWindow function_MainWindow;
               
                public bool triggerCodeFound(String theData)
                {
                        if ((theData.IndexOf("World") > (-1)))
                        {
                                this.function_MainWindow.sayHello("Silly Person!");
                                return (true);
                        }
                        return (false);
                }
        }
}

---

I am a C/C++ coder by trade, and just learning C#. In C/C++, this is a rather simple concept for me to grasp, however, C# is kicking my arse and laughing all the way.

Any help to avenge this temporary nemesis would be awesome.

Thanks!

In line 5 of your first block of code you create an instance variable tCodes. Where is the code that assigns an object to this instance variable?
In line 5 of your second block of code you create an instance variable function_MainWindow. Where is the code that assigns an object to this instance variable?

This is basic OO stuff, applies to C++, C#, etc.

I think that I figured it out. Well, it *seems* to be working, although I'm not sure if I could/should have done it a better way.

Here's what I have now:

In "MainWindow.xaml.cs":

Code:

---

namespace programX
{
        public partial class MainWindow : Window
        {
                public MainWindow()
                {
                        InitializeComponent();
                }
               
                protected internal void doSomething()
                {
                        triggerDerivedClass tCodes = new triggerDerivedClass();
                       
                        if (tCodes.triggerCodeFound(this, "Hello World"))
                                return;
                       
                        Console.WriteLine("Didn't find it");
                }               
               
                public void sayHello(string message)
                {
                        StringBuilder msg = new StringBuilder();
                        msg.Append("Hello ");
                        msg.Append(message);
                       
                        // *should* write "Hello Silly Person!"
                        Console.WriteLine(msg.ToString());
                }
        }
}

---

In "TriggerCodes.cs":

Code:

---

namespace programX
{
        public abstract class triggerBaseClass
        {
                public abstract bool triggerCodeFound(MainWindow sender, String theData);
        }
        public class triggerDerivedClass : triggerBaseClass
        {               
                public override bool triggerCodeFound(MainWindow sender, String theData)
                {
                        if ((theData.IndexOf("World") > (-1)))
                        {
                                sender.sayHello("Silly Person!");
                                return (true);
                        }
                        return (false);
                }
        }
}

---