好处：
防止sql注入；占用内存更少
例子：
传参有业务查询条件startDate,endDate,A,每页数据个数pageSize,当前查询页码pageIndex
string sql = @"select A,B,C
FROM sc with(nolock)
WHERE IsDelete!=1 {0}
ORDER BY A DESC
OFFSET @pageSize*(@pageIndex-1) ROWS FETCH NEXT @pageSize ROWS ONLY";
StringBuilder sb = new StringBuilder();
List<SqlParameter> parameters = new List<SqlParameter>();
DateTime now = DateTime.Now;
parameters.Add(new SqlParameter("@startDate", startDate==null?new DateTime(now.Year,now.Month,now.Day):startDate));
parameters.Add(new SqlParameter("@endDate", endDate == null ? new DateTime(now.Year, now.Month, now.Day).AddDays(1) : DateTime.Parse(endDate.ToString()).AddDays(1)));
parameters.Add(new SqlParameter("@A", A));
parameters.Add(new SqlParameter("@pageSize", pageSize));
parameters.Add(new SqlParameter("@pageIndex", pageIndex));
if (startDate != null)
sb.Append(" and sc.Date>=@startDate ");
if (endDate != null)
sb.Append(" and sc.Date<@endDate ");
if (!string.IsNullOrEmpty(A))
sb.Append(" and sc.A=@A ");
sql = string.Format(sql, sb);
//查询数据库
