使用反射创建类型的实例

Question

I am trying to use reflection to create an instance of one of my classes. The interface for the class (IInstructions) has one variable shown below.

    string[] Operands { get; set; }

I am trying to create an instance of this class using reflection that has the operand variables set. The code I have got so far is shown below.

        Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
        Console.WriteLine(operands[0]);
        foreach (Assembly a in assemblies)
        {
            Type[] typeArray = a.GetTypes();
            foreach (Type type in typeArray)
            {
                if (opcode.Equals(type.Name, StringComparison.InvariantCultureIgnoreCase))
                {
                    Object dynamicObj = Activator.CreateInstance(type);
                    instruction = (IInstructionWithOperand)dynamicObj;

                }
            }
        }

This, so far searches through the loaded assemblies and retrieves the correct assembly and type for that assembly. However, I'm unsure how to set the variable for this type and correctly create an instance of it?

Answer 1

If the type is always IInstructionWithOperand then you could declare

IInstructionWithOperand instruction;

and then assign it exactly as you have:

instruction = (IInstructionWithOperand)dynamicObj;

Or, suppose all of the code above is within a function. You could make IInstructionWithOperand the return type of the function, like

IInstructionWithOperand GetInstruction(string opcode)
{
    Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
    Console.WriteLine(operands[0]);
    foreach (Assembly a in assemblies)
    {
        Type[] typeArray = a.GetTypes();
        foreach (Type type in typeArray)
        {
            if (opcode.Equals(type.Name, StringComparison.InvariantCultureIgnoreCase))
            {
                Object dynamicObj = Activator.CreateInstance(type);
                return (IInstructionWithOperand)dynamicObj;
            }
        }
    }
} 

You don't have to declare a variable within the function. When you call the function, it will look like this:

var instruction = GetInstruction(someOpCode);

and the declared type of instruction will be IInstructionWithOperand .

That's probably a good idea anyway because it will keep parts of your code separate. One function creates an instance of a class that implements IInstructionWithOperand , and another function (or class) uses it to do something.