Cannot create/invoke delegate

TcpClient.cs

Code:

---

namespace TCP_Communication
{
        class TcpClient
        {
                // ...
                public delegate void OnDataAvailable(char[] data);
                // ...
        }
}

---

Program.cs

Code:

---

using System;
using System.Collections.Generic;
using System.Text;

namespace TCP_Communication
{
        class Program
        {
                static void Main(string[] args)
                {
                        // ...
                        Client.OnDataAvailable = DataArrived;
                        // ...
                }
                public void DataArrived(char[] newdata)
                {
                        // empty for now
                }
        }
}

---

Error:

Quote:

---

'OnDataAvailable': cannot reference a type through an expression; try 'TCP_Communication.TcpClient.OnDataAvailable' instead

---

Yes, I tried 'TCP_Communication.TcpClient.OnDataAvailable' instead even though it is obviously wrong:

Program.cs

Code:

---

using System;
using System.Collections.Generic;
using System.Text;

namespace TCP_Communication
{
        class Program
        {
                static void Main(string[] args)
                {
                        // ...
                        TCP_Communication.TcpClient.OnDataAvailable = DataArrived;
                        // ...
                }
                public void DataArrived(char[] newdata)
                {
                        // empty for now
                }
        }
}

---

This time it gives this error message:

Quote:

---

'TCP_Communication.TcpClient.OnDataAvailable' is a 'type', which is not valid in the given context

---

I read the article in MSDN about C# delegates, but still I can't find what I'm missing.

Please help me guys, how can I fix this code?

Your TcpClient class should be public.

Code:

---

        public class TcpClient
        {
                // ...
                public delegate void OnDataAvailable(char[] data);
                // ...
        }

---

Quote:

---

Originally Posted by dannystommen

Your TcpClient class should be public.

Code:

---

        public class TcpClient
        {
                // ...
                public delegate void OnDataAvailable(char[] data);
                // ...
        }

---

---

Adding "public" keyword did not change anything.

As the error message says in the second case, the line

public delegate void OnDataAvailable(char[] data);

declares a type, not a member field.

You can think of it as a class that represents a collection of methods with a specific signature - but in this case, the C# language provides a special mechanism and a special keyword ("delegate") used for such declarations.

As with nested classes, you can nest a delegate within a class, but you don't have to - you can declare it within the namespace.

For example:

Code:

---

namespace Test
{
    // declares a TYPE VoidMethod...
    public delegate void VoidMethod();

    public class MyClass
    {
        // declares a nested TYPE MyClass.WorkerMethod...
        public delegate void WorkerMethod(object obj);
    }
}

---

But these are just type declarations, they don't really do anything.

Once you've defined the delegate types, you can have member fields of those types.

Code:

---

namespace Test
{
    // declares a TYPE VoidMethod...
    public delegate void VoidMethod();

    public class MyClass
    {
        // declares a nested TYPE MyClass.WorkerMethod...
        public delegate void WorkerMethod(object obj);

        // fields
        private VoidMethod voidMethodDelegate = null;  // this one will, for example, be used internally, so I won't expose it
        private WorkerMethod workerDelegate = null;

        // A property to expose the workerDelegate field.
        public WorkerMethod Worker
        {
            get { return workerDelegate; }
            set { workerDelegate = value; }
        }
    }
}

---

To access this delegate from another class you would write:

Code:

---

MyClass temp = new MyClass();
temp.Worker += new SomeMethodName;

//...

// later on, invoke the delegate...
temp.Worker(someParameter);

---

Note that the "+=" is generally used to add methods, and "-=" is used to remove them. The invocation runs all the associated methods. You can initialize/modify the delegates in the constructor, or in some other convenient place.