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How to get current ApplicationContext instance at run time

, 3 Aug 2004
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Step by step instruction how to get current ApplicationContext instance at run time

Introduction

While I was working on one of my projects, I got into a situation where I needed to get the current ApplicationContext instance from one part of my software. I started my research on MSDN, then on the Internet. As some of you probably already know by reading this article, I did not find the results I was looking for. I cannot understand why there is no easy way to get the current ApplicationContext instance with regular MS defined properties or methods. I have, however, created a simple solution.

  1. Create a new class inherited from ApplicationContext.
    public class CurrentAppContext : ApplicationContext
    {
        CurrentAppContext()
        {
        }
    }

    If you need to set the Main-Form for ApplicationContext while initializing, you can add the constructor like that as well.

    CurrentAppContext(Form AppMainForm)
    {
        this.MainForm = AppMainForm;
    }
  2. Create a public static field pointed to our CurrentAppContext form inside the class.
    public class CurrentAppContext : ApplicationContext
    {
      public static CurrentAppContext CurrentContext;
    
      CurrentAppContext()
      {
      }
    
      CurrentAppContext(Form AppMainForm)
      {
          this.MainForm = AppMainForm;
      }
    }
  3. Because static class fields exist only once and are not created again, when we create a new class instance, we can initialize our field from the constructor.
    public class CurrentAppContext : ApplicationContext
    {
      public static CurrentAppContext CurrentContext;
    
      CurrentAppContext()
      {
        CurrentContext = this;
      }
    
      CurrentAppContext(Form AppMainForm) : this()
      {
        this.MainForm = AppMainForm;
      }
    }
  4. If you need to get the ApplicationContext at run time, we will create a new instance of CurrentAppContext and get CurrentContext, which is exactly what we need. (See below.)
    CurrentAppContext _curContext = (new CurrentAppContext()).CurrentContext;

OOPS!  Because we initialize CurrentAppContext() again and point CurrentContext to new CurrentAppContext instance, CurrentContext will be referring to new instance, but not to our current ApplicationContext. We have to add If statement to the constructor and make sure that if the CurrentContext is not null we do not make a new assignment. Also, let’s convert public field to Read Only property.

Final class will look something like this: (See below)

public class CurrentAppContext : ApplicationContext
{
  private static CurrentAppContext _currContext;

  CurrentAppContext()
  {
    if (_currContext == null)
    {
      _currContext = this;
    }
  }

  CurrentAppContext(Form AppMainForm) : this()
  {
    this.MainForm = AppMainForm;
  }

  public CurrentAppContext  CurrentContext
  {
    get
    {
      return currContext;
    }
  }
}

Now you can create it inside Main() as usual and get it from any part of your software. If necessary, you can extend it with new fields and methods.

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About the Author

alphacon

United States United States
No Biography provided

Comments and Discussions

 
GeneralThank you! Pinmembervoiger25-Jul-08 2:23 
QuestionBut why? PinmemberLabrat0024-Aug-04 13:37 

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