[ACCEPTED]-Activator.CreateInstance - How to create instances of classes that have parameterized constructors-.net-3.5

Accepted answer
Score: 51

There is an overload that accepts arguments 2 as a params object[]:

object obj = Activator.CreateInstance(typeof(StringBuilder), "abc");

Would this do? Alternative, you can 1 use reflection to find the correct constructor:

Type[] argTypes = new Type[] {typeof(string)};
object[] argValues = new object[] {"abc"};
ConstructorInfo ctor = typeof(StringBuilder).GetConstructor(argTypes);
object obj = ctor.Invoke(argValues);
Score: 8

I eventually ended up doing something like 7 this - some of the commentors hinted towards 6 this solution anyway.

I basically iterated 5 through all available constructors and chose 4 the simplest. I then created null data 3 to pass into the ctor (for what Im using 2 it for this approach is fine)

Part of the 1 code looks a little like this

// If we have a ctor that requires parameters then pass null values
if (requiresParameters)
    List<object> parameters = new List<object>();
    ParameterInfo[] pInfos = constructorInfos[0].GetParameters();

    foreach (ParameterInfo pi in pInfos)

    return constructorInfos[0].Invoke(parameters.ToArray());
Score: 2

I'm using this method to get around an issue I ran into, and 1 it seems to be working exactly as I hoped. :)

object instance = Activator.CreateInstance(
    BindingFlags.NonPublic | BindingFlags.Instance,
    new object[] { stringname, pop, push, operand, type, size, s1, s2, ctrl, endsjmpblk, stack },
Score: 0

Activator.CreateInstance also has a whole 8 bunch of overloads, one you might want to 7 check out is ( Type type, params object[] args 6 ). Simply supply the required constructor 5 arguments to the second parameter of this 4 call.

Make sure you handle exceptions here 3 though, as it's easy to pass incorrect parameters 2 in or for something to change in the type's 1 constructors later on that breaks it..

Score: 0

As an alternative to Activator.CreateInstance, FastObjectFactory 9 in the linked url preforms better than Activator 8 (as of .NET 4.0 and significantly better 7 than .NET 3.5. No tests/stats done with 6 .NET 4.5). See StackOverflow post for stats, info 5 and code. Note that some modifications may 4 need to be done based upon the number of 3 ctor params. The code provided only allows 2 1 ctor param but can be modified to have 1 more than 1. See comments in code.

How to pass ctor args in Activator.CreateInstance or use IL?

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