C#生成sql分页语句

/// <summary>
/// 生成分页语句
/// </summary>
/// <param name="tableName">数据表名</param>
/// <param name="whereString">Where后面的条件</param>
/// <returns></returns>
public String GetPageString(string field, string tableName, int _pagerIndex, int _pagerSize, string WhereString, string _orderString)
{
StringBuilder sql = new StringBuilder();
if (string.IsNullOrEmpty(_orderString))//排序不能为空
{

_orderString = " id desc";
}
sql.Append("(select row_number() over (order by " + _orderString + ") as rowId," + field + "from " + tableName);//查询语句
if (!string.IsNullOrEmpty(WhereString))
{
sql.Append(" where " + WhereString);
}
if (_pagerIndex > 0)
{
_pagerIndex = _pagerIndex - 1;
}
int StartRecord = (_pagerIndex) * _pagerSize + 1;
int EndRecord = StartRecord + _pagerSize - 1;
string dd = sql.ToString();
sql.Clear();
sql.Append(" select * from " + dd + ") as t where rowId between " + StartRecord + " and " + EndRecord);
//if (!string.IsNullOrEmpty(_orderString))
//{
// sql.Append(" ORDER BY " + _orderString);
//}
return sql.ToString();
}