用于SqlServer数据库的SqlServerHelper.cs类，及其调用例子

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Configuration;
using System.Data;
using System.Data.SqlClient;

namespace demo
{
    public abstract class SqlServerHelper
    {
        public static string ConnString = string.Empty;

        public static string Conn_Config_Str_Name = string.Empty;

        public static string Conn_Server = string.Empty;
        public static string Conn_DBName = string.Empty;
        public static string Conn_Uid = string.Empty;
        public static string Conn_Pwd = string.Empty;

        private static string _ConnString
        {
            get
            {
                if (!string.IsNullOrEmpty(ConnString))
                    return ConnString;

                object oConn = ConfigurationManager.ConnectionStrings[Conn_Config_Str_Name];
                if (oConn != null && oConn.ToString() != "")
                    return oConn.ToString();

                return string.Format(@"server={0};database={1};uid={2};password={3}", Conn_Server, Conn_DBName, Conn_Uid, Conn_Pwd);
            }
        }

        // 测试连接
        public static bool TestConn()
        {
            SqlConnection myConn = null;
            bool bResult = false;
            try
            {
                myConn = new SqlConnection(_ConnString);
                myConn.Open();
            }
            catch (Exception ex)
            {
            }
            finally
            {
                if (myConn != null && myConn.State.ToString() == "Open")
                    bResult = true;
            }

            myConn.Close();

            return bResult;
        }

        // 取datatable
        public static DataTable GetDataTable(out string sError, string sSQL)
        {
            DataTable dt = null;
            sError = string.Empty;

            try
            {
                SqlConnection conn = new SqlConnection(_ConnString);
                SqlCommand comm = new SqlCommand();
                comm.Connection = conn;
                comm.CommandText = sSQL;
                SqlDataAdapter dapter = new SqlDataAdapter(comm);
                dt = new DataTable();
                dapter.Fill(dt);
            }
            catch (Exception ex)
            {
                sError = ex.Message;
            }

            return dt;
        }

        // 取dataset
        public static DataSet GetDataSet(out string sError, string sSQL)
        {
            DataSet ds = null;
            sError = string.Empty;

            try
            {
                SqlConnection conn = new SqlConnection(_ConnString);
                SqlCommand comm = new SqlCommand();
                comm.Connection = conn;
                comm.CommandText = sSQL;
                SqlDataAdapter dapter = new SqlDataAdapter(comm);
                ds = new DataSet();
                dapter.Fill(ds);
            }
            catch (Exception ex)
            {
                sError = ex.Message;
            }

            return ds;
        }

        // 取某个单一的元素
        public static object GetSingle(out string sError, string sSQL)
        {
            DataTable dt = GetDataTable(out sError, sSQL);
            if (dt != null && dt.Rows.Count > 0)
            {
                return dt.Rows[0][0];
            }

            return null;
        }

        // 取最大的ID
        public static Int32 GetMaxID(out string sError, string sKeyField, string sTableName)
        {
            DataTable dt = GetDataTable(out sError, "select isnull(max([" + sKeyField + "]),0) as MaxID from [" + sTableName + "]");
            if (dt != null && dt.Rows.Count > 0)
            {
                return Convert.ToInt32(dt.Rows[0][0].ToString());
            }

            return 0;
        }

        // 执行 insert,update,delete 动作，也可以使用事务
        public static bool UpdateData(out string sError, string sSQL, bool bUseTransaction = false)
        {
            int iResult = 0;
            sError = string.Empty;

            if (!bUseTransaction)
            {
                try
                {
                    SqlConnection conn = new SqlConnection(_ConnString);
                    if (conn.State != ConnectionState.Open)
                        conn.Open();
                    SqlCommand comm = new SqlCommand();
                    comm.Connection = conn;
                    comm.CommandText = sSQL;
                    iResult = comm.ExecuteNonQuery();
                }
                catch (Exception ex)
                {
                    sError = ex.Message;
                    iResult = -1;
                }
            }
            else // 使用事务
            {
                SqlTransaction trans = null;
                try
                {
                    SqlConnection conn = new SqlConnection(_ConnString);
                    if (conn.State != ConnectionState.Open)
                        conn.Open();
                    trans = conn.BeginTransaction();
                    SqlCommand cmd = new SqlCommand();
                    cmd.Connection = conn;
                    cmd.CommandText = sSQL;
                    cmd.Transaction = trans;
                    iResult = cmd.ExecuteNonQuery();
                    trans.Commit();
                }
                catch (Exception ex)
                {
                    sError = ex.Message;
                    iResult = -1;
                    trans.Rollback();
                }
            }

            return iResult > 0;
        }

    }
}