Parameter is not valid

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C#

SQL-Server

i have save image in ms sql database with datatype Image but when i try to fetch image from database it show me error parameter is not valid
Code Is:

string str = "Select * from Document where CustId=" + cmbCustomerName.SelectedValue.ToString() + "";
                  con.Open();
                SqlCommand cmd = new SqlCommand(str,con);
                SqlDataReader dr = null;
                dr = cmd.ExecuteReader();
                if (dr.HasRows)
                {
                    while (dr.Read())
                    {
                        byte[] picarr = (byte[])dr["Photo"];
                        MemoryStream ms = new MemoryStream(picarr);
                        ms.Seek(0, SeekOrigin.Begin);
                        picPhoto.Image = Image.FromStream(ms);
                        
                    }
                }
                con.Close();