在上篇文章写到我们为什么要分层.有很多读者提出来很多宝贵的意见.让我受益匪浅,深深的感觉到自己的水平"还有很大的提升空间".首先感谢这些朋友们,我会进一步总结完善自己的想法.
截取了部分朋友的留言,感谢他们:
这次我用对比的方式描述一下,分层到底分出了什么.俗话说:有分必有合,那么它是把什么合到了一起.
首先写出两个没有分层的demo:
<1>查询信息demo
1: Imports System.Data.SqlClient
2: Public Class Form2
3: Private sqlCon As String = "Data Source=LSH;Initial Catalog=ComputerLab;User ID=sa;Password=123456"
4: '查询数据库信息信息
5: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
6:
7: Dim conStr As New SqlConnection '数据库连接对象
8: Dim sqlCom As SqlCommand '数据库执行对象
9: Dim Res As DialogResult '消息提示框返回类型
10: Dim dr As SqlDataReader 'dataReader对象
11: Dim dt As New DataTable 'Datatable对象
12:
13: Dim sql As String = "select * from TableName where Name=@name" 'sql查询语句
14: conStr.ConnectionString = sqlCon '给数据库连接对象赋值
15: sqlCom = New SqlCommand(sql, conStr) '给数据库执行对象赋值
16: sqlCom.Parameters.Add("@name", SqlDbType.VarChar, TextBox1.Text) '给sql语句参数赋值
17:
18: Res = MessageBox.Show("是否查询", "提示", MessageBoxButtons.OKCancel)
19: '判断是否查询
20: If Res = DialogResult.Yes Then
21: Try
22: conStr.Open()
23: dr = sqlCom.ExecuteReader '执行查询语句
24: dt.Load(dr)
25: Catch ex As Exception
26: Throw ex
27: Finally
28: If Not IsNothing(conStr) Then '如果数据库打开,则关闭数据库
29: conStr.Close()
30: End If
31: End Try
32: End If
33:
34: MsgBox(dt.Rows.Count) '显示查询到的行数
35: End Sub
<2>添加信息demo
1: Imports System.Data.SqlClient
2:
3: Public Class Form1
4: Private sqlCon As String = "Data Source=LSH;Initial Catalog=ComputerLab;User ID=sa;Password=123456"
5: '向数据库添加信息
6: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
7: Dim bln As Boolean = False '存储返回值
8: Dim conStr As New SqlConnection '数据库连接对象
9: Dim sqlCom As SqlCommand '数据库执行对象
10: Dim Res As DialogResult '消息提示框返回类型
11:
12: Dim sql As String = "insert into TableName(Name) value(@Name)" 'sql插入语句
13: conStr.ConnectionString = sqlCon '给数据库连接对象赋值
14: sqlCom = New SqlCommand(sql, conStr) '给数据库执行对象赋值
15: sqlCom.Parameters.Add("@Name", SqlDbType.VarChar, TextBox1.Text) '给sql语句参数赋值
16:
17: Res = MessageBox.Show("是否添加", "提示", MessageBoxButtons.OKCancel)
18: '判断是否同意插入
19: If Res = DialogResult.Yes Then
20: Try
21: conStr.Open()
22: bln = sqlCom.ExecuteNonQuery '执行插入语句
23: Catch ex As Exception
24: bln = False
25: Finally
26: If Not IsNothing(conStr) Then '如果数据库打开,则关闭数据库
27: conStr.Close()
28: End If
29: End Try
30: End If
31:
32: MsgBox(bln) '提示返回信息
33: End Sub
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