C# static Dbhelper 

 1  public class SQLHelper {
 2         private static string connString = "";
 3         public static int Update(string sql) {
 4             SqlConnection conn = new SqlConnection(connString);
 5             SqlCommand cmd = new SqlCommand(sql, conn);
 6             try {
 7                 conn.Open();
 8                 int i = cmd.ExecuteNonQuery();
 9                 conn.Close();
10                 return i;
11             }
12             catch (Exception ex) {
13                 throw new Exception(ex.Message);
14             }
15             finally {
16                 conn.Close();
17             }
18         }
19         public static object GetSingleResult(string sql) {
20             SqlConnection conn = new SqlConnection(connString);
21             SqlCommand cmd = new SqlCommand(sql, conn);
22             try {
23                 conn.Open();
24                 object result = cmd.ExecuteScalar();
25                 conn.Close();
26                 return result;
27             }
28             catch (Exception ex) {
29                 throw ex;
30             }
31             finally {
32                 conn.Close();
33             }
34 
35         }
36         public static SqlDataReader GetReader(string sql) {
37             SqlConnection conn = new SqlConnection(connString);
38             SqlCommand cmd = new SqlCommand(sql, conn);
39             SqlDataReader objReader = null;
40             try {
41                 conn.Open();
42                 objReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
43                 return objReader;
44             }
45             catch (Exception ex) {
46                 conn.Close();
47                 throw ex;
48             }
49         }
50     }
View Code

在使用static中不可以使用Using来关闭数据库连接，因为static是静态的，只可以初始化一次，如果使用using释放，之后它为空，会出现未将对象初始化

posted @ 2019-07-03 17:47  学海无涯，天道酬勤  阅读(234)  评论(0)  编辑  收藏  举报