防SQL注入：生成参数化的通用分页查询语句

      前些时间看了玉开兄的“如此高效通用的分页存储过程是带有sql注入漏洞的”这篇文章，才突然想起某个项目也是使用了累似的通用分页存储过程。使用这种通用的存储过程进行分页查询，想要防SQL注入，只能对输入的参数进行过滤，例如将一个单引号“'”转换成两个单引号“''”，但这种做法是不安全的，厉害的黑客可以通过编码的方式绕过单引号的过滤，要想有效防SQL注入，只有参数化查询才是最终的解决方案。但问题就出在这种通用分页存储过程是在存储过程内部进行SQL语句拼接，根本无法修改为参数化的查询语句，因此这种通用分页存储过程是不可取的。但是如果不用通用的分页存储过程，则意味着必须为每个具体的分页查询写一个分页存储过程，这会增加不少的工作量。

      经过几天的时间考虑之后，想到了一个用代码来生成参数化的通用分页查询语句的解决方案。代码如下：

    public class PagerQuery
    {
        private int _pageIndex;
        private int _pageSize = 20;
        private string _pk;
        private string _fromClause;
        private string _groupClause;
        private string _selectClause;
        private string _sortClause;
        private StringBuilder _whereClause;
        public DateTime DateFilter = DateTime.MinValue;

        protected QueryBase()
        {
            _whereClause = new StringBuilder();
        }

        /**//// <summary>
        /// 主键
        /// </summary>
        public string PK
        {
            get { return _pk; }
            set { _pk = value; }
        }

        public string SelectClause
        {
            get { return _selectClause; }
            set { _selectClause = value; }
        }

        public string FromClause
        {
            get { return _fromClause; }
            set { _fromClause = value; }
        }

        public StringBuilder WhereClause
        {
            get { return _whereClause; }
            set { _whereClause = value; }
        }

        public string GroupClause
        {
            get { return _groupClause; }
            set { _groupClause = value; }
        }

        public string SortClause
        {
            get { return _sortClause; }
            set { _sortClause = value; }
        }

        /**//// <summary>
        /// 当前页数
        /// </summary>
        public int PageIndex
        {
            get { return _pageIndex; }
            set { _pageIndex = value; }
        }

        /**//// <summary>
        /// 分页大小
        /// </summary>
        public int PageSize
        {
            get { return _pageSize; }
            set { _pageSize = value; }
        }

        /**//// <summary>
        /// 生成缓存Key
        /// </summary>
        /// <returns></returns>
        public override string GetCacheKey()
        {
            const string keyFormat = "Pager-SC:{0}-FC:{1}-WC:{2}-GC:{3}-SC:{4}";
            return string.Format(keyFormat, SelectClause, FromClause, WhereClause, GroupClause, SortClause);
        }

        /**//// <summary>
        /// 生成查询记录总数的SQL语句
        /// </summary>
        /// <returns></returns>
        public string GenerateCountSql()
        {
            StringBuilder sb = new StringBuilder();

            sb.AppendFormat(" from {0}", FromClause);
            if (WhereClause.Length > 0)
                sb.AppendFormat(" where 1=1 {0}", WhereClause);

            if (!string.IsNullOrEmpty(GroupClause))
                sb.AppendFormat(" group by {0}", GroupClause);

            return string.Format("Select count(0) {0}", sb);
        }

        /**//// <summary>
        /// 生成分页查询语句，包含记录总数
        /// </summary>
        /// <returns></returns>
        public string GenerateSqlIncludeTotalRecords()
        {
            StringBuilder sb = new StringBuilder();
            if (string.IsNullOrEmpty(SelectClause))
                SelectClause = "*";

            if (string.IsNullOrEmpty(SortClause))
                SortClause = PK;

            int start_row_num = (PageIndex - 1)*PageSize + 1;

            sb.AppendFormat(" from {0}", FromClause);
            if (WhereClause.Length > 0)
                sb.AppendFormat(" where 1=1 {0}", WhereClause);

            if (!string.IsNullOrEmpty(GroupClause))
                sb.AppendFormat(" group by {0}", GroupClause);

            string countSql = string.Format("Select count(0) {0};", sb);
            string tempSql =
                string.Format(
                    "WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY {0}) as row_number,{1}{2}) Select * from t where row_number BETWEEN {3} and {4};",
                    SortClause, SelectClause, sb, start_row_num, (start_row_num + PageSize - 1));

            return tempSql + countSql;
        }

        /**//// <summary>
        /// 生成分页查询语句
        /// </summary>
        /// <returns></returns>
        public override string GenerateSql()
        {
            StringBuilder sb = new StringBuilder();
            if (string.IsNullOrEmpty(SelectClause))
                SelectClause = "*";

            if (string.IsNullOrEmpty(SortClause))
                SortClause = PK;

            int start_row_num = (PageIndex - 1)*PageSize + 1;

            sb.AppendFormat(" from {0}", FromClause);
            if (WhereClause.Length > 0)
                sb.AppendFormat(" where 1=1 {0}", WhereClause);

            if (!string.IsNullOrEmpty(GroupClause))
                sb.AppendFormat(" group by {0}", GroupClause);

            return
                string.Format(
                    "WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY {0}) as row_number,{1}{2}) Select * from t where row_number BETWEEN {3} and {4}",
                    SortClause, SelectClause, sb, start_row_num, (start_row_num + PageSize - 1));
        }
    }

使用方法：

PagerQuery query = new PagerQuery();
query.PageIndex = 1;
    query.PageSize = 20;
    query.PK = "ID";
    query.SelectClause = "*";
    query.FromClause = "TestTable";
    query.SortClause = "ID DESC";

    if (!string.IsNullOrEmpty(code))
    {
     query.WhereClause.Append(" and ID= @ID");
    }

a) GenerateCountSql ()方法生成的语句为：
Select count(0) from TestTable Where 1=1 and ID= @ID

b) GenerateSql()方法生成的语句为：
WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY ECID DESC) as row_number, * from TestTable where 1=1 and ID= @ID) Select * from t where row_number BETWEEN 1 and 20

c) GenerateSqlIncludetTotalRecords()方法生成的语句为：
WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY E.ECID DESC) as row_number,* from TestTable where 1=1 and ID= @ID) Select * from t where row_number BETWEEN 1 and 20;Select count(0) from ECBasicInfo where 1=1 and ID= @ID;

注意：以上代码生成的SQL语句是曾对SQL SERVER 2005以上版本的，希望这些代码对大家有用