Compiling new classes at run-time that inherit from a pre-defined interface

Question

Hi All I am using the code below to compile code at run-time to allow the user to create their own classes within the app. The problem I am having is that I would like the classes to inherit from an existing interface so that I can more easily handle them throughout the app. My existing code succesfully creates the code for and compiles the user-defiined classes and I can then create instances of the classes using Assembly CreateInstance(). What I am not able to do ithus far is get the user-defined classes to succesfully inherit from my interface. I have tried adding the namepsace name of my app to the code being compiled and declaring the class with public class UserClass : MyNameSpace.MyInterface or with public class UserClass : MyInterface but the run-time compiler always raises an error. I have tried reproducing the code for the interface and placing it in user-defined class code which will allow it to compile. While this seems to work when I create an instance of the user-defined class it cannot be cast to the type of the interface and has clearly not inherited from it. Any suggestions or help would be greatly appreciated! Following is my code for compiling at run-time in case that helps. Thank you JP Code for compiling user-defined classes at run-time: ICodeCompiler comp = (new CSharpCodeProvider().CreateCompiler()); CompilerParameters cp = new CompilerParameters(); cp.ReferencedAssemblies.Add(system.dll); cp.GenerateExecutable = false; cp.GenerateInMemory = true; CompilerResults cr = comp.CompileAssemblyFromSource(cp code); if (cr.Errors.HasErrors) { StringBuilder error = new StringBuilder(); error.Append(Error Compiling Expression: ); foreach (CompilerError err in cr.Errors) { error.AppendFormat({0}
 err.ErrorText); } throw new Exception(Error Compiling Expression:  + error.ToString()); }

shimtanny · Answer

Hi I post my example maybe you can see some differences to your code: Main app: using System; using System.IO; using System.Text; using System.Reflection; using Microsoft.CSharp; using System.CodeDom.Compiler; using System.Diagnostics; namespace Test { class Class1 { /// /// The main entry point for the application. /// [STAThread] static void Main(string[] args) { ICodeCompiler comp = (new CSharpCodeProvider().CreateCompiler()); CompilerParameters cp = new CompilerParameters(); cp.ReferencedAssemblies.Add(system.dll); cp.ReferencedAssemblies.Add(Test.exe); cp.GenerateExecutable = false; cp.GenerateInMemory = true; // FileInfo file = new FileInfo(@..\..\Person.cs); // StreamReader sr = file.OpenText(); // string code = sr.ReadToEnd(); // sr.Close(); // CompilerResults cr = comp.CompileAssemblyFromSource(cp code); CompilerResults cr = comp.CompileAssemblyFromFile(cp @..\..\Person.cs); if (cr.Errors.HasErrors) { foreach (CompilerError err in cr.Errors) { Debug.WriteLine(err.ErrorText); } } else { object o = cr.CompiledAssembly.CreateInstance(Test.Person); Type t = o.GetType(); Type[] interfaces = t.GetInterfaces(); IPerson p = (Test.IPerson) o; } } } public interface IPerson { string Name { get; set; } } } Seperate source file containing class Person: using System; namespace Test { public class Person : IPerson { private string name; public Person() : this(string.Empty) { } public Person(string name) { this.name = name; } public string Name { get { return this.name; } set { this.name = value; } } } } Simon

jppollak · Answer

Thanks Simon Adding a reference to my applications assembly did help in that I didn't need to add the interface code to the user-defined code that I am compiling. However the problem still exists that after I have generated the class and created an instance of it my application code does not recognize that it inherits from the desired interface. In the simplified code below IsInstanceIfType() always returns false and the type casting always raises an error. object o = Activator.CreateInstance(MyNewTypeInheritsFromMyInterface); bool b = typeof(MyInterface).IsInstanceOfType(o); MyInterface myInterfaceObject = (MyInterface)o; Thanks JP

shimtanny · Answer

Hi I assume that you defined MyInterface twice one time to compile it with UserClass and another time to have access in your main application. But those interfaces are not the same because they are in different assemblies (in the main appl. and in the runtime generated assembly). So just add the assembly to the compiler options that contains the MyInterface. cp.ReferencedAssemblies.Add(AssemblyThatContainsMyInterface.exe); Maybe this helps. Simon