转：SQLHelper类，泛型+反射
自己一直都是学习使用asp.net mvc框架+linQ的，所以对于ado.net基本上一无所知，最近接了个小项目，所以打算学习+用ado.net来完成。
首先就想到了，写一个通用点SQLHelper类来辅助完成数据库的操作。
1.定义一个类：public class SQLHelper<T> where T : class, new()
说明：SQLHelper有一个T的泛型类型，T属于class,new()，否则T就不能T t =new T()这样使用new关键字了！
2.之后就是数据库的链接和关闭等操作：
1 /// <summary>
2 /// 链接数据库字符串
3 /// </summary>
4 public static string strConnectionString = ConfigurationManager.ConnectionStrings["DataConnectionString"].ToString();
5
6 /// <summary>
7 /// 数据库连接
8 /// </summary>
9 public SqlConnection Connection = null;
10
11 public SQLHelper()
12 {
13 OpenConnect();
14 }
15
16 /// <summary>
17 /// 打开数据库连接
18 /// </summary>
19 public void OpenConnect()
20 {
21 if (Connection == null || Connection.State != System.Data.ConnectionState.Open)
22 {
23 Connection = new SqlConnection(strConnectionString);
24
25 Connection.Open();
26 }
27 }
28
29 /// <summary>
30 /// 关闭数据库连接
31 /// </summary>
32 public void CloseConnect()
33 {
34 if (Connection != null && Connection.State != System.Data.ConnectionState.Closed)
35 {
36 Connection.Close();
37 }
38 }
3.对数据库进行读写操作。
1
2 /// <summary>
3 /// 执行查询语句
4 /// </summary>
5 /// <param name="strSQL">SQL语句</param>
6 /// <param name="obQuery">SQL参数的值</param>
7 /// <returns></returns>
8 public SqlDataReader ExecReader(string strSQL, object obQuery)
9 {
10 SqlCommand command = new SqlCommand(strSQL, Connection);
11
12 if (obQuery != null)
13 {
14 PropertyInfo[] pis = obQuery.GetType().GetProperties();
15
16 foreach (var p in pis)
17 {
18 command.Parameters.Add(new SqlParameter(p.Name, p.GetValue(obQuery, null)));
19 }
20 }
21
22 SqlDataReader reader = command.ExecuteReader();
23
24 return reader;
25 }
26
27 /// <summary>
28 /// 执行返回单值的查询语句
29 /// </summary>
30 /// <param name="strSQL">SQL语句</param>
31 /// <param name="obQuery">SQL参数的值</param>
32 /// <returns></returns>
33 public object ExecSingleValue(string strSQL, object obQuery)
34 {
35 SqlCommand command = new SqlCommand(strSQL, Connection);
36
37
38 if (obQuery != null)
39 {
40 PropertyInfo[] pis = obQuery.GetType().GetProperties();
41
42 foreach (var p in pis)
43 {
44 command.Parameters.Add(new SqlParameter(p.Name, p.GetValue(obQuery, null)));
45 }
46 }
47
48 return command.ExecuteScalar();
49 }
50
51 /// <summary>
52 /// 执行非查询语句
53 /// </summary>
54 /// <param name="strSQL">SQL语句</param>
55 /// <param name="obQuery">SQL参数的值</param>
56 /// <returns></returns>
57 public int ExecNoQuery(string strSQL, object obQuery)
58 {
59 SqlCommand command = new SqlCommand(strSQL, Connection);
60
61 if (obQuery != null)
62 {
63 PropertyInfo[] pis = obQuery.GetType().GetProperties();
64
65 foreach (var p in pis)
66 {
67 command.Parameters.Add(new SqlParameter(p.Name, p.GetValue(obQuery, null)));
68 }
69 }
70
71 return command.ExecuteNonQuery();
72 }
解释:
//判断是SQL语句中参数的值对象是否为空
//例如：new{Id=1,Name="Test"}
if (obQuery != null)
{
//获取SQL语句中参数的值对象中的属性类型和值
PropertyInfo[] pis = obQuery.GetType().GetProperties();
//循环遍历对象中的属性
foreach (var p in pis)
{
//利用反射将Id,Name等值填充到SQL语句中的参数中
command.Parameters.Add(new SqlParameter(p.Name, p.GetValue(obQuery, null)));
}
}
查询操作中，返回的是SQLDataReader对象，如何获取我们所需要的列表，分页，单个实体呢？
4.返回列表List<T>，还是利用泛型+反射
1 /// <summary>
2 /// 获取列表
3 /// </summary>
4 /// <param name="strSQL">SQL语句</param>
5 /// <param name="obQuery">SQL参数的值</param>
6 /// <returns></returns>
7 public List<T> GetList(string strSQL, object obQuery)
8 {
9 //调用执行查询语句函数，返回SqlDataReader
10 SqlDataReader reader = ExecReader(strSQL, obQuery);
11 //定义返回的列表
12 List<T> list = new List<T>();
13 //定义T类型的实体
14 T model = new T();
15 //获取T类型实体的属性类型和值
16 PropertyInfo[] pis = model.GetType().GetProperties();
17 //获取数据库返回的列数
18 int intColCount = reader.FieldCount;
19 //遍历SqlDataReader
20 while (reader.Read())
21 {
22 //定义
23 int value_number = 0;
24 //重新实例化T
25 model = new T();
26 //从数据库拿出一条数据后，循环遍历T类型的属性类型和值
27 for (int i = 0; i < intColCount; i++)
28 {
29 //判断第一列是否为row_number，此为分页使用
30 if (reader.GetName(i) == "row_number") value_number++;
31 //设置T对应属性的值
32 pis[i].SetValue(model, reader.GetValue(value_number), null);
33 value_number++;
34 }
35 //将T添加到列表中
36 list.Add(model);
37 }
38
39 return list;
40 }
5.返回分页，获取PagesList<T>
5.1。分页实体类：
1 public class PagedList<T> : List<T>
2 {
3 /// <summary>
4 /// 分页编号
5 /// </summary>
6 public int intPageIndex { get; set; }
7
8 /// <summary>
9 /// 分页大小
10 /// </summary>
11 public int intPageSize { get; set; }
12
13 /// <summary>
14 /// 分页数
15 /// </summary>
16 public int intPages { get; set; }
17
18 /// <summary>
19 /// 总元素的个数
20 /// </summary>
21 public int intTotalCount { get; set; }
22
23 /// <summary>
24 /// 此分页元素的个数
25 /// </summary>
26 public int intCount { get; set; }
27
28 /// <summary>
29 /// 是否有下一页
30 /// </summary>
31 public bool HasNextPage { get; set; }
32
33 /// <summary>
34 /// 是否有上一页
35 /// </summary>
36 public bool HasPrPage { get; set; }
37
38 public PagedList(int intPageIndex, int intPageSize)
39 {
40 this.intPageIndex = intPageIndex;
41 this.intPageSize = intPageSize;
42 }
43 }
5.2。实现分页，返回PagesList<T>
1 /// <summary>
2 /// 获取分页
3 /// </summary>
4 /// <param name="strTotalSQL">总共个数的SQL</param>
5 /// <param name="obTotalQuery">总共个数的SQL参数的值</param>
6 /// <param name="strSQL">分页的SQL</param>
7 /// <param name="obQuery">分页SQL参数的值</param>
8 /// <param name="intPageIndex">分页编号</param>
9 /// <param name="intPageSize">分页大小</param>
10 /// <returns></returns>
11 public PagedList<T> GetPageList(string strTotalSQL, object obTotalQuery, string strSQL, object obQuery, int intPageIndex, int intPageSize)
12 {
13 //定义分页对象的编号和大小
14 PagedList<T> pageList = new PagedList<T>(intPageIndex, intPageSize);
15 //执行获取单个值的函数，设置分页对象的总元素
16 pageList.intTotalCount = (int)ExecSingleValue(strTotalSQL, obTotalQuery);
17 //设置分页对象的分页数
18 if (pageList.intTotalCount % intPageSize == 0) pageList.intPages = pageList.intTotalCount / intPageSize;
19 else pageList.intPages = pageList.intTotalCount / intPageSize + 1;
20 //定义列表，调用获取列表的函数获取此分页的元素
21 List<T> list = GetList(strSQL, obQuery);
22 //将列表元素添加到分页对象当中
23 pageList.AddRange(list);
24 //设置分页对象是否有上一页和下一页
25 pageList.HasNextPage = pageList.intPageIndex < pageList.intPages ? true : false;
26 pageList.HasPrPage = pageList.intPageIndex > 1 ? true : false;
27
28 return pageList;
29 }
6.获取单个实体类：T
1 /// <summary>
2 /// 获取单个实体
3 /// </summary>
4 /// <param name="strSQL">SQL语句</param>
5 /// <param name="obQuery">SQL参数的值</param>
6 /// <returns></returns>
7 public T GetTM(string strSQL, object obQuery)
8 {
9 //调用执行查询语句，返回SqlDataReader
10 SqlDataReader reader = ExecReader(strSQL, obQuery);
11 //新建一个T类型
12 T model = new T();
13 //获取T类型的属性类型和值
14 PropertyInfo[] pis = model.GetType().GetProperties();
15 //获取数据库返回数据的列数
16 int intColCount = reader.FieldCount;
17 //读取数据，填充T
18 if (reader.Read())
19 {
20 int value_number = 0;
21 for (int i = 0; i < intColCount; i++)
22 {
23 pis[i].SetValue(model, reader.GetValue(value_number), null);
24 value_number++;
25 }
26 }
27
28 return model;
29 }
7.调用方法：ResumeTM为数据库表的实体类
1 public List<ResumeTM> GetResumeByJobInfoId(int intJobInfoId)
2 {
3 SQLHelper<ResumeTM> helper = new SQLHelper<ResumeTM>();
4
5 string strSQL = @"select * from Resume where FirstJobId=@JobInfoId or SecondJobId=@JobInfoId order by CreateTime desc";
6
7 object obQuery = new { JobInfoId=intJobInfoId};
8
9 List<ResumeTM> list = helper.GetList(strSQL, obQuery);
10
11 helper.CloseConnect();
12
13 return list;
14 }
15
16 public ResumeTM GetResumeById(int intId)
17 {
18 SQLHelper<ResumeTM> helper = new SQLHelper<ResumeTM>();
19
20 string strSQL = @"select * from Resume where Id=@Id";
21
22 object obQuery = new { Id=intId};
23
24 ResumeTM tm = helper.GetTM(strSQL, obQuery);
25
26 helper.CloseConnect();
27
28 return tm;
29 }
30
31 public PagedList<ResumeTM> GetResume(int intPageIndex, int intPaegSize)
32 {
33 SQLHelper<ResumeTM> helper = new SQLHelper<ResumeTM>();
34
35 string strTotalCount = @"select count(*) from Resume";
36
37 string strSQL = @"select * from
38 (
39 select row_number() over(order by CreateTime desc) as row_number,* from Resume
40 ) as t0
41 where t0.row_number between @intPageSize*(@intPageIndex-1)+1 and @ingPageSize*@intPageIndex";
42 object obQuery = new { intPageSize=intPaegSize,intPageIndex=intPageIndex};
43
44 PagedList<ResumeTM> list = helper.GetPageList(strTotalCount, null, strSQL, obQuery, intPageIndex, intPaegSize);
45
46 helper.CloseConnect();
47
48 return list;
49 }
50
51 public void Delete(int intId)
52 {
53 SQLHelper<ResumeTM> helper = new SQLHelper<ResumeTM>();
54
55 string strSQL = @"delete from Resume where Id=@Id";
56
57 object obQuery = new { Id=intId};
58
59 helper.ExecNoQuery(strSQL, obQuery);
60
61 helper.CloseConnect();
62 }
哈哈。。写好了。。。有什么写得不好的，希望大家多多指教。拍拍砖。。。
