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POWriting COM object in C# and using it from C#
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  1. POWriting COM object in C# and using it from C#
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    copied!<p>I would like to implement a COM object in C# and also use it in C# (besides C++ and others).</p> <p>Here is the code of the DLL implementing the COM object :</p> <pre><code>namespace TestComServer { [ComVisible(true), Guid("565D8202-6C0F-4AAB-B0F6-49719CD13045"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown) ] public interface ITestObject { void DoSomething(); } [ ComVisible(true), GuidAttribute("21293767-A713-49E2-968E-7DDE0B0DAB94"), ClassInterface(ClassInterfaceType.None) ] public class TestObject : ITestObject { public TestObject() { } public void DoSomething() { } } } </code></pre> <p>I've used gacutil at add the DLL to the global assembly cache.</p> <p>The EXE uses the COM object in the following way (like I successfully did with some COM objects implemented in C++):</p> <pre><code>[ ComImport(), Guid("565D8202-6C0F-4AAB-B0F6-49719CD13045"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown) ] public interface ITestObject { [PreserveSig ] void DoSomething(); } [ComImport, Guid("21293767-A713-49E2-968E-7DDE0B0DAB94")] public class TestObject { } private void button1_Click(object sender, EventArgs e) { object o = new TestObject(); ITestObject t = (ITestObject)o; t.DoSomething(); } </code></pre> <p>When executing the line <em>object o = new TestObject();</em>, I get an InvalidCastException. What is wrong with this code?</p> <blockquote> <p>An unhandled exception of type 'System.InvalidCastException' occurred in Test.exe Additional information: Das Objekt des Typs "TestComServer.TestObject" kann nicht in Typ "TestObject" umgewandelt werden.</p> </blockquote>
 

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