Summit Software

How to create instance of interface in host in VSTA Add-in

I have an interface in host application. I want create an instance in Add-in [Visual Basic]. Is there any way?

I tried

Dim obj As New IMyInterface

but it requires two argument

global::System.AddIn.Contract.IContract

and 

global::Microsoft.VisualStudio.Tools.Applications.TypeInfrastructureManager

 

How to get these instances in Add-in vb file?

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Nitin Umap
Software Professional

nitinumap,
There are two issues here:

1) 
>Dim obj As New IMyInterface
You cannot create an instance of an interface, instead you can declare a variable of the interface's type and set it to an instance of a class that implements the interface.

Dim obj As IMyInterface = New ClassThatImplementsTheInterface

2)
Vsta add-ins should use a factory method to get a host object instead of creating an instance.  This is so that all objects are created on the host side and marshaled across through the proxy layer instead of relying on the add-in to provide management for the object. 

Below is some code that shows how to do this on the host and add-in side.  For more information on this, you may want to check out our EventSample which demonstrates how to implement this. 

I hope this helps, please let me know if you have any questions.
Thanks,
-Melody

'Host (Application class)
Public Function getIMyInterface() As IMyInterface
   Dim obj As IMyInterface = New ClassThatImplementsTheInterface
   Return obj
End Function

Public Class ClassThatImplementsTheInterface
  Implements IMyInterface
End Class

Public Interface IMyInterface
End Interface

'Add-in
Private Sub AppAddIn_Startup(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Startup

    'create a new object using the factory method
    Dim iObj As IMyInterface = Application.getIMyInterface("hello")

End Sub