I have question relating to my list and switch statement in my code

I want to thank in advance anyone who's able to help me here. Hi my question is relating to my code for my list and Case . The method that i've used RemoveRange only removes the numbers that i have added to my list at certain indexes. Do i need to use a different method or how do i remove it at randomly without removing it at certain indexes. meaning currently if i curently generate a random index and a random number to remove. current if i generate a random index of 2 and random number to remove of 3. it will remove index 3, 4, 5. how do i randomly say. randomly remove at any position. For exampl.. i have numbers 1,2,3,4,5,6. i have a random count of 3 i want to randomly remove 1, 4, 6 instead of removing at certain index. The next question deals with my case statement. currently i have my switch statement related to the count on my list. If the count is equal to 2 i send it to one of my case statement. What i want to do is have the count related to multiple Case statements. Meaning if I return a count of 2 have my application randomly choose one the multiple case statement that i have set for that count. I don't know how to set this case statment properly or if i should be using some other statement such as if or if my doing my switch statemtent all wrong.. ..

Here is my code for my question..

Code:

                List firstlist = new List();
                Random listRand = new Random();

              //  Predicate mypred = new Predicate();
               
                //We add these number from the textbox to a list
                firstlist.Add(numTxt1);
                firstlist.Add(numTxt2);
                firstlist.Add(numTxt3);
                firstlist.Add(numTxt4);
                firstlist.Add(numTxt5);
                firstlist.Add(numTxt6);

                int size = listRand.Next(0,2);
                int item = listRand.Next(3,5);
                firstlist.RemoveRange(size,item);
                //int size = firstlist.Count;
                //while (size > 0)
                //{

                //    size--;
                //    int index = (new Random()).Next(0, size);
                //    int elem = firstlist[index];
                //    firstlist[index] = firstlist[size];

                //    MessageBox.Show(elem.ToString());
                
                
                //}
                //listRand.Next(1, 3);

                //(4 & (1 + mynumb.Next())) - 1
                int listint01 = 1,
                    listint02 = 2,
                    listint03 = 3;
                listint01 = firstlist.Count;
                listint02 = firstlist.Count;
                listint03 = firstlist.Count;
                

                switch (firstlist.Count)
                {
                    case 1: 
                        firstlist[0] = firstlist[0] + 1; 
                        break;
                       
                    //case 1:
                    //    firstlist[0] = firstlist[0] - 1;
                    //    break;

                    //case 1:
                    //    firstlist[0] = firstlist[0];
                    //    break;

                    case 2:
                        // Add one
                        firstlist[0] = firstlist[0] + 1;
                        firstlist[1] = firstlist[1] - 1;
                        break;

                    //case 2:
                    //    // Add one
                    //    firstlist[0] = firstlist[0] - 1;
                    //    firstlist[1] = firstlist[1] + 1;
                    //    break;

                    //case 2:
                    //    // Add one
                    //    firstlist[0] = firstlist[0] - 1;
                    //    firstlist[1] = firstlist[1];
                    //    break;

                    //case 2:
                    //    // Add one
                    //    firstlist[0] = firstlist[0] + 1;
                    //    firstlist[1] = firstlist[1];
                    //    break;

                    case 3:
                        // Add one
                        firstlist[0] = firstlist[0] + 1;
                        firstlist[1] = firstlist[1] - 1;
                        firstlist[2] = firstlist[2];                               
                        break;

                    //case 3:
                    //    // Subtract one
                    //    firstlist[0] = firstlist[0] - 1;
                    //    firstlist[1] = firstlist[1] + 1;
                    //    firstlist[2] = firstlist[2];
                    //    break;

                    //case 3:
                    //    // Leave as is
                    //    firstlist[0] = firstlist[0];
                    //    firstlist[1] = firstlist[1];
                    //    firstlist[2] = firstlist[2] - 1;
                        
                    //    break;      
                    //case 3:
                    //    firstlist[0] = firstlist[0];
                    //    firstlist[1] = firstlist[1];
                    //    firstlist[2] = firstlist[2] + 1;
                    //    break;

                }