Extend a function to accept a list - C#

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C#

I have the following function that accepts an array of strings or an array object. I want to extend this function in such a way that it also accepts a list of objects and a list of strings.

Cannot find a way of how to implement it. Any help would be appreciated.

public override void Run()
        {
            log.Trace(this, String.Format(LoggingConstants.StartCustomStep, this.GetType().Name));

            object[] realList;
            object rawList = (object)GetInput("List", typeof(object));
            object item = (object)GetInput("Item", typeof(object));

            if (rawList is object[])
            {
                realList = (object[])rawList;
            }
            else if (rawList is string)
            {
                realList = (rawList as string).Split(";".ToCharArray());
            }
            else
                throw new ArgumentException("Invalid List argument supplied.  Must be an array or string.");

            string status = StatusConstants.Fail;;
            if (item != null)
            {
                foreach (object listItem in realList)
                {
                    if (item.Equals(listItem))
                    {
                        status = StatusConstants.Pass;
                        break;
                    }
                }
            }

            SetOutput("Status", status);

            log.Trace(this, String.Format(LoggingConstants.EndCustomStep, this.GetType().Name));
        }

What I have tried:

nothing that managed to work. However someone advised to start by checking the list then use else if to check the array