Instancing a class with an internal constructor

An alternative would be to nominate the calling assembly as a "friend" assembly.

Simply add this to AssemblyInfo.cs file of the assembly containing the internal constructor:

[assembly: InternalsVisibleTo("Calling.Assembly")]

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If you don't have access to the assembly, you can also call the constructor directly (using Reflection):

MyClass obj = (MyClass) typeof(MyClass).GetConstructor(
                  BindingFlags.NonPublic | BindingFlags.Instance,
                  null, Type.EmptyTypes, null).Invoke(null);

A FormatterServices.GetUninitializedObject method exists (Namespace: System.Runtime.Serialization), it supposedly calls no constructors, if you really want to try out that approach.

This is a method derived from this answer:

public static T CreateInstance<T>(params object[] args)
{
    var type = typeof (T);
    var instance = type.Assembly.CreateInstance(
        type.FullName, false,
        BindingFlags.Instance | BindingFlags.NonPublic,
        null, args, null, null);
    return (T) instance;
}

Example usage (this is a Kinect SDK type that I needed to create for unit tests):

DiscreteGestureResult a = CreateInstance<DiscreteGestureResult>(false, false, 0.5f);