C# Reflection - Type error

Question

string assembly = "Ektron.Cms.ObjectFactory.dll";
string asspath = path + "bin\\" + assembly;
Assembly run_obj = Assembly.LoadFrom(@asspath);
paraObj[0] = run_obj.GetType(
    "Ektron.Cms.Search.SearchContentProperty",
    true,
    true
).GetProperty("Language");

string equalExp = "Ektron.Cms.Search.Expressions.EqualsExpression";
Type objclass = run_obj.GetType(equalExp, true, true);       
object objObj = Activator.CreateInstance(objclass, paraObj);

Activator.CreateInstance(objclass, paraObj) throws an error:

System.Reflection.RuntimeParameterInfo can't be implicitly convert into Ektron.Cms.Search.Expresions.PropertyExpression

Answer 1

The value stored in paraObj[0] is of type RuntimeParameterInfo, whereas the constructor for EqualsExpression expects an object of type PropertyExpression. You need to ensure that the types of the objects in paraObj can be bound to a suitable constructor for Activator to be able to instantiate a new object.

To resolve your problem you need to create an instance of PropertyExpression and use this as the first element in your paraObj array:

string assembly = "Ektron.Cms.ObjectFactory.dll";
string asspath = path + "bin\\" + assembly;
Assembly run_obj = Assembly.LoadFrom(@asspath);

PropertyInfo propertyInfo = run_obj.GetType("Ektron.Cms.Search.SearchContentProperty", true, true).GetProperty("Language");
PropertyExpression propertyExpression = new PropertyExpression(propertyInfo); // create the property expression here, I am unsure how to instantiate it.
paraObj[0] = propertyExpression;
paraObj[1] = longValue;

string equalExp = "Ektron.Cms.Search.Expressions.EqualsExpression";
Type objclass = run_obj.GetType(equalExp, true, true);       
object objObj = Activator.CreateInstance(objclass, paraObj);

Answer 2

You are not supplying the type the Constructor is expecting from your code, it's clear that you are passing PropertyInfo.

If you need a value from the property the PropertyInfo is pointing to you would have to use PropertyInfo.GetValue

I'm speculating (as I do not have the Ektron code) from your code snippet, you should do something similar to this -

var propInfo  = run_obj.GetType(
                  "Ektron.Cms.Search.SearchContentProperty",
                   true,true).GetProperty("Language");

paraObj[0] = propInfo.GetValue(null,null)  //depending on the requirement