if string item is not in string array

Question

I have a string array. I need to display buttons based on if the selected item is in the array. I need to know how to tell the program if "(array.NOT Contains("string"))". Please can anybody help me?? Thanks in advance

My code:

    List<string> activationids = new List<string>();
    foreach (ModuleActivation moduleactivation in activationid)
         activationids.Add(moduleactivation.ActivationID);

    string gvselectActID = GridView1.SelectedRow.Cells[1].Text;

    if (activationids.Contains(gvselectActID))
    {
      activateInsert.Visible = true;
      activateUpdate.Visible = false;
      deactivate.Visible = true;
    }
    else if (activationids."NOT" Contains(gvselectActID))
    {
      activateInsert.Visible = false;
      activateUpdate.Visible = true;
      deactivate.Visible = false;
    }
    else
    {
     activateInsert.Visible = false;
     activateUpdate.Visible = false;
     deactivate.Visible = false;
    }
  } 

Answer 1

Change:

else if (activationids."NOT" Contains(gvselectActID)) 

to

else if (!activationids.Contains(gvselectActID))