Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

Class Library Delegate and Event Issues?

Posted on 2012-12-27
6
Medium Priority
?
276 Views
Last Modified: 2012-12-27
I usually built a Class Libary within a Windows Forms project. I can test the class by using buttons and textboxes. I send the 'Status' messages to Form1 using a Delegate and Event as illustrated in the code example below. The problem arises when deploying the Class Libarary to be used with another executable. The unused Delegate causes an 'Object Reference' error if it's not instanctiated in the new executable. I want the option for class library status message returns if needed, but don't want to demand the delegate instanciation.

   [class library (.dll)]
   public delegate void JobManagerStatusEventHandler(string statusMessage);

    public static class JobSetup
    {
        public static event JobManagerStatusEventHandler StatusMessage;
    }
0
Comment
Question by:pointeman
  • 2
  • 2
  • 2
6 Comments
 
LVL 8

Expert Comment

by:Crashman
ID: 38723887
then, you must initialice the object in your dll
0
 
LVL 75

Assisted Solution

by:käµfm³d 👽
käµfm³d   👽 earned 2000 total points
ID: 38723952
I'm not sure I fully understand your question, but in C# you should be checking to see if any event handlers have been attached to your event by comparing the event to null prior to invoking it.

e.g.

public static void SomeMethod()
{
    if (StatusMessage != null)
    {
        StatusMessage("Hello World!");
    }
}

Open in new window

0
 
LVL 8

Expert Comment

by:Crashman
ID: 38723986
you must create the object, because the class is static is created in memory and you must create one instance for related objects

http://msdn.microsoft.com/en-us/library/79b3xss3%28v=vs.80%29.aspx
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:pointeman
ID: 38724060
Q, Anyway to use a cool ?? operator instead?

        StatusMessage(??  : "Hello World!");
0
 
LVL 75

Accepted Solution

by:
käµfm³d   👽 earned 2000 total points
ID: 38724161
What would you use it for? The coalesce operator ( ?? ) returns the first non-null argument in its parameter list. You haven't really shown something that can be null (outside of the event). If you had something like:

public delegate void JobManagerStatusEventHandler(string statusMessage);
private static string message = null;

public static class JobSetup
{
    public static event JobManagerStatusEventHandler StatusMessage;
}

public static void SomeMethod()
{
    if (StatusMessage != null)
    {
        StatusMessage(message ?? "Hello World!");
    }
}

Open in new window


...then sure.
0
 

Author Closing Comment

by:pointeman
ID: 38724219
Cool, thanks again
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Entity Framework is a powerful tool to help you interact with the DataBase but still doesn't help much when we have a Stored Procedure that returns more than one resultset. The solution takes some of out-of-the-box thinking; read on!
The article shows the basic steps of integrating an HTML theme template into an ASP.NET MVC project
Is your data getting by on basic protection measures? In today’s climate of debilitating malware and ransomware—like WannaCry—that may not be enough. You need to establish more than basics, like a recovery plan that protects both data and endpoints.…
Despite its rising prevalence in the business world, "the cloud" is still misunderstood. Some companies still believe common misconceptions about lack of security in cloud solutions and many misuses of cloud storage options still occur every day. …
Suggested Courses

772 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question