Cast received object to a List<object> or IEnumerable<object>

Answer 1

C# 4 will have covariant and contravariant template parameters, but until then you have to do something nongeneric like

IList collection = (IList)myObject;

Answer 2

You need to type cast using as operator like this.

private void MyMethod(object myObject)  
{  
if(myObject is IEnumerable)  
{
    List<object> collection = myObject as(List<object>); 
    ... do something   
}  
else  
{  
    ... do something  
}  
}