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POHow can I pass an instance of a .NET COM object from Delphi to another .NET COM object?
 

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  1. POHow can I pass an instance of a .NET COM object from Delphi to another .NET COM object?
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    <p>I have a legacy app written in Delphi 7. We are adding new modules to the app. The modules are written in Visual Studio 2010, .NET 4, C#, and exposed to the app through COM.</p> <p>I have successfully defined a class, registered the assembly, exported the type library, imported the type library into Delphi, created the COM client in Delphi and executed the module. Now comes the tricky part: I want to pass <em>another</em> object (that has been defined-registered-exported-blah-blah-blah as above) as a parameter to a method on the first module.</p> <p><strong>.NET</strong></p> <pre><code>[ComVisible(true)] [InterfaceType(ComInterfaceType.InterfaceIsDual)] [Guid("11111111-1111-1111-1111-AAAAAAAAAAAA")] public interface IUserMaintenance { bool AssignUser(IUserInfo); } [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] [Guid("11111111-1111-1111-1111-BBBBBBBBBBBB")] public class UserMaintenance: IUserMaintenance { private IUserInfo _UserInfo; public bool AssignUser(IUserInfo userInfo) { _UserInfo = userInfo; LoadUser(); } private void LoadUser() { //load user data from database using _UserInfo.UserName } } [ComVisible(true)] [InterfaceType(ComInterfaceType.InterfaceIsDual)] [Guid("22222222-2222-2222-2222-AAAAAAAAAAAA")] public interface IUserInfo { void Initialize(string userName); string UserName { get; } } [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] [Guid("22222222-2222-2222-2222-BBBBBBBBBBBB")] public class UserInfo: IUserInfo { public string UserName { get; private set }; public void Initialize(string userName) { UserName = userName; } } </code></pre> <p>Assuming that I have separate classes implementing each interface, and the assemblies containing those classes compile and register successfully, I import the type libraries into Delphi creating UserMaintenance_TLB.pas and UserInfo_TLB.pas. However, I see something unexptected: while the interfaces that I defined in .NET exist (the ones beginning with "I"), Delphi has generated another set of interfaces (the ones beginning with "_"). Delphi does <em>not</em> use the I-interfaces that I declared in .NET at all.</p> <p><strong>Delphi</strong></p> <pre><code>UserMaintenance_TLB.pas // *********************************************************************// // Forward declaration of types defined in TypeLibrary // *********************************************************************// IUserMaintenance = interface; IUserMaintenanceDisp = dispinterface; _UserMaintenance = interface; _UserMaintenanceDisp = dispinterface; UserInfo_TLB.pas // *********************************************************************// // Forward declaration of types defined in TypeLibrary // *********************************************************************// IUserInfo = interface; IUserInfoDisp = dispinterface; _UserInfo = interface; _UserInfoDisp = dispinterface; </code></pre> <p>Delphi has also created the corresponding Delphi types:</p> <pre><code>// *********************************************************************// // OLE Server Proxy class declaration // Server Object : TUserMaintenance // Help String : // Default Interface: _UserMaintenance // Def. Intf. DISP? : No // Event Interface: // TypeFlags : (2) CanCreate // *********************************************************************// TUserMaintenance = class(TOleServer) private FIntf: _UserMaintenance; function GetDefaultInterface: _UserMaintenance; protected procedure InitServerData; override; function Get_ToString: WideString; public constructor Create(AOwner: TComponent); override; destructor Destroy; override; procedure Connect; override; procedure ConnectTo(svrIntf: _UserMaintenance); procedure Disconnect; override; function Equals(obj: OleVariant): WordBool; function GetHashCode: Integer; function GetType: _Type; WordBool AssignUser(IUserInfo userInfo); property DefaultInterface: _UserMaintenance read GetDefaultInterface; property ToString: WideString read Get_ToString; published end; </code></pre> <p>What I would like to do is create an instance of TUserMaintenance, and then pass an instance of TUserInfo to it. However, two things are immediately obvious: The Delphi class TUserInfo does NOT implement IUserInfo, and the DefaultInterface is the new interface that Delphi generated, _UserInfo. I cannot declare my UserInfo variable as type IUserInfo because TUserInfo does not implement the interface. Nor can I declare it as type _UserInfo because UserMaintenance.LoadUser expects an IUserInfo instance.</p> <p>Admittedly, this is a much simplified example of my actual issue, but I think that it sufficiently illustrates the problem.</p> <p>So my question is this: is there any way for me to force the interface type in Delphi to remain consistent with the interface that is declared in .NET? Or is there <em>another</em> way that I can pass an instance of UserInfo to UserMaintenance?</p>
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    1. USMason Wheeler
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