Trimend() issues

I am tring to trim an string from a string builder but it is not trimming the character

 StringBuilder sb = new StringBuilder();
            if (emailSent == 1)
            {
                ListViewSelectedItemCollection col = radlvEmp.SelectedItems;

                
                foreach (ListViewDataItem item in col)
                {
                    sb.Append(Convert.ToString(item.Value) + ", ");
                }
                
            }
            string s = sb.ToString();
            s = s.ToString().Trim();
            s.TrimEnd(',');

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the value is still me.me@yahoo.com,