Unable to invoke method during reflection

I am trying to load the assembly from GAC(third party tool), because i need to load the assembly only if it is particular version , and i am trying to invoke a method in it, but it is throwing TargetInvocationException

PFC below

a = Assembly.LoadFrom("C:\\WINDOWS\\assembly\\GAC\\ESRI.ArcGIS.AxReaderControl\\9.1.0.722__8fc3cc631e44ad86\\ESRI.ArcGIS.AxReaderControl.dll");

AppDomain.CurrentDomain.Load(a.GetName());
Type myType = a.GetTypes()[0];
MethodInfo myMethod = myType.GetMethod("CheckDocument");
object obj = a.CreateInstance(myType.FullName);
object[] objparam2 = new object[1];

foreach (ParameterInfo param in myMethod.GetParameters())
{
objparam2[0] = "testr";
}
try
{
object x = (bool)myMethod.Invoke(obj, objparam2);
}
catch (TargetInvocationException tie)
{
if (tie.InnerException is NotImplementedException)
{
//I am getting the inner exception as System.Windows.Forms.AxHost+InvalidActiveXStateException
}
}


kindly help me in resolving th same . thanks