Deleting a document using ContentService API doesn't refresh cache

Question

In Umbraco 7, I used ContentService API to insert, update or delete documents. After inserting or updating a document, the correct content shows immediately, but after deleting, removed data can be viewed because of the cache. To clear cache, I delete DistCache folder's data from App_data.

How can I refresh the cache programmatically?

Here is my code:

public string DeleteStudent(int studentID)
{
    IContentService service = ApplicationContext.Current.Services.ContentService;
    if (studentID != 0)
    {
        IContent student = service.GetById(studentID);

        if (student != null && student.ContentType.Alias == "dtStudent")
        {
            service.Delete(student);
            return "Done!";
        }
    }
    return "Error!";
}

Answer 1

As @Harvey said in the comment, using service.MoveToRecycleBin works fine. That method will unpublish the content, then move it to the recycle bin.

Final code:

public string DeleteStudent(int studentID)
{
    IContentService service = ApplicationContext.Current.Services.ContentService;
    if (studentID != 0)
    {
        IContent student = service.GetById(studentID);

        if (student != null && student.ContentType.Alias == "dtStudent")
        {
            service.MoveToRecycleBin(student);
            return "Done!";
        }
    }
    return "Error!";
}