Programming a Programming Computer Game – .Net Run Time Type Creator

 public static T CreateType(string source,
IEnumerable<string> assemblies,
out List compilationErrors)
where T : class

It will attempt to create an instance of the type T from the source passed in. The source will be compiled with references to all the assemblies in the assemblies parameter. So for example you could do this with it.

namespace RunTimeTypeCreator.Tests 
{ 
public class RunTimeTypeCreatorTests 
{ 
public static bool TestVariable = false; 
public void Example() 
{ 
const string source = @" 
using RunTimeTypeCreator.Tests; 
public class TestTypeClass : RunTimeTypeCreatorTests.ITestType 
{ 
public bool Success { get { return RunTimeTypeCreatorTests.TestVariable; } } 
}"; 
List<string> compilationErrors; 
var type = RunTimeTypeCreator.CreateType<ITestType>(source, 
new[] { "RunTimeTypeCreator.Tests.dll" }, //the name of this assembly
out compilationErrors); 
TestVariable = false; 
//will print false 
Console.WriteLine(type.Success) 
TestVariable = true; 
//will print true 
Console.WriteLine(type.Success) 
} 
public interface ITestType 
{ 
bool Success { get; } 
} 
} 
} 

Which is kind a cool I think. Here's a quick run through of how it works, this just shows the code minus bits of validation and error reporting, so if you want the full thing I would recommend getting it from github

var csc = new CSharpCodeProvider(); 
var parameters = new CompilerParameters 
{ 
//we don't want a physical executable in this case 
GenerateExecutable = false, 
//this is what allows it to access variables in our domain 
GenerateInMemory = true 
}; 
//add all the assmeblies we care about 
foreach (var assembly in assemblies) 
parameters.ReferencedAssemblies.Add(assembly); 
//compile away, will load the class into memory 
var result = csc.CompileAssemblyFromSource(parameters, source); 

//we compiled succesfully so now just use reflection to get the type we want 
var types = result.CompiledAssembly.GetTypes() 
.Where(x => typeof(T).IsAssignableFrom(x)).ToList(); 
var parameterlessConstructor = types.First().GetConstructor(new Type[] { }); 

//create the type and return 
return (T)Activator.CreateInstance(types.First());

Full code is available here on github. I also had some other code around validating what the user was doing, Making sure they weren't trying to access the file system, open ports or creating memory leaks/recursive loops. I'll try and clean this up and post it at a future date.