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Help clarifying a textbook example project

Posted on 2006-07-11
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Last Modified: 2010-04-23
I have been studying creating custom user controls, and am about to start the "Hands-on" programming example.
However, it's as if it's introducing a new feature that wasn't explained in the text.  Could someone clarify what is meant by changing the root namespace in the following:

"Create a Windows user control that ... <blah> <blah> <blah>
This control must make the data ... available to the form...
To share a Person structure between the control and the form, each project must be declared in the same namespace.  By default, each project is created in its own root namespace.  The easiest and best way to change this is to display the Project Properties dialog box and change the root namespace before building the project."

So - why exactly is changing the namespace necessary?  
And what exactly would one change it to?
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Question by:sirbounty
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4 Comments
 
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Expert Comment

by:Carl Tawn
ID: 17082353
They're basically saying that your UserControl and your Test Harness project should both be in the same namespace, presumably to simplify the example.

You can change it to whatever you want, just so long as they are the same. So, for example, you might have a line like:

    Namespace MyProject.UserControlSample

At the top of your UserControl class and the form in your test harness project.
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by:sirbounty
ID: 17082383
Hmm - maybe my ignorance stems from the usage of 'namespace'.  What is it and how's it used in my project(s)?

Why would they need to share the same namespace and/or what would be the limitation(s) if they did not?
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Carl Tawn earned 250 total points
ID: 17082496
Namespaces are simply a way of grouping related objects, they are also used to avoid clashes in object names.

So, if you have two classes both called "Person", if they were in the same namespace then if you used something like:

    Dim p As New Person()

Then the compiler wouldn't know which Person class you meant. However, if you seperate them into seperate namespaces:

    Namespace Customers
        Class Person
        End Class
    End Namespace

    Namespace Contacts
        Class Person
        End Class
    End Namespace

Then you could use:

    Dim p As New Customers.Person()         '// Explicitly state the namespace

Or:

    Imports Customers

    ....

    Dim p As new Person()          '// No need to explictly state namespace because we have "Imported" it


If they are in different namespaces then it just means that you have to Import the namespace in which the UserControl lives, whereas, if they are in the same namespace then you don't need to.
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by:sirbounty
ID: 17082526
Thanx! :^)
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