两个数组比较，得到不变，新增，删除的数据。

private void btnCompare_Click(object sender, EventArgs e)
{
    string[] orgList = this.textBox1.Text.Trim().Split(',');
    string[] lastList = this.textBox2.Text.Trim().Split(',');

    string lastStr = "";
    //没变的
    var noChangeList = orgList.Intersect(lastList);
    if (noChangeList != null)
    {
        lastStr += "没变的：\t" + string.Join(",", noChangeList);
    }

    //新增的
    var addList = lastList.Except(orgList);
    if (addList != null)
    {
        lastStr += "\r\n新增的：\t" + string.Join(",", addList);
    }

    //删除的
    var delList = orgList.Except(lastList);
    if (delList != null)
    {
        lastStr += "\r\n删除的：\t" + string.Join(",", delList);
    }

    this.textBox3.Text = lastStr;
}