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    <p>Everything behaves exactly as it should :)</p> <p>In your C++ project, you are allowed to access all the methods declared on your <code>IEntity</code> interface, which there are none.</p> <p>Your implementation, i.e. <code>AQSEntity</code> class, should implement all the <code>IEntity</code> members. The methods which are now declared in that class are member of the class, they are not related to <code>IEntity</code> in any way.</p> <p>This means you need to declare all the required methods inside <code>IEntity</code> interface and then implement them in <code>AQSEntity</code>. Notice that you are also exposing the fields of the class, not the methods. You will have to define methods (or properties, which will get converted to methods on C++ side) and then implement them. Something like:</p> <pre><code>public interface IEntity { public string RecoveryDBName { get; } } </code></pre> <p>You also have to specify <code>[MarshalAs]</code> attributes in the interface, although <code>UnmanagedType.BStr</code> is default for strings, so you can omit them.</p> <p>EDIT:</p> <p>based on comments, it seems that <code>IEntity</code> is just a marker interface, not intended to be exposed as an API (attributes might be better option here, as <code>IEntity</code> won't be used on client side anyway).</p> <p>In this case there are two options:</p> <p>1) better approach, although it requires more work: derive <code>IAQSEntity</code> interface from <code>IEntity</code>, declare methods on it, and implement that on <code>AQSEntity</code> class</p> <p>2) less work, but more brittle: Mark <code>AQSEntity</code> as <code>ClassInterfaceType.AutoDual</code> instead of <code>ClassInterfaceType.None</code> - this will expose the members to COM clients, but will be much harder to version and it will also expose the base type members.</p> <p>Here's what I would choose:</p> <pre><code>[ClassInterface(ClassInterfaceType.None)] ... [Entity] // instead of IEntity marker interface public class AQSEntity : IAQSEntity { public string RecoveryDbName { get; } } [Guid("...")] [InterfaceType(ComInterfaceType.InterfaceIsDual)] public interface IAQSEntity // no base interface IEntity! { string RecoveryDbName { get; } } </code></pre> <p>The only drawback of using <code>Entity</code> attribute instead of <code>IEntity</code> marker interface is if you want to use the interface as constraint for generics</p>
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    1. USZdeslav Vojkovic
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    1. COThere are other classes implementing IEntity. If I add properties and methods to IEntity, those classes cannot inherit from IEntity.
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    2. COThen you need `IAQS` interface derived from entity. COM aside, how would you access `AQSEntity` members via `IEntity` in C#? no way - it seems to be a marker interface in your case. Another option is using `ClassInterfaceType.AutoDual` instead of `ClassInterfaceType.None`, but it is considered a bad practice.
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    3. COI am changing my design as per the suggestions in this post. Thanks
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