vb.net—SQLHelper类的使用

SqlHelper用于简化你重复的去写那些数据库连接SqlConnection,SqlCommand,SqlDataReader等等。SqlHelper 封装过后通常是只需要给方法传入一些参数如数据库连接字符串，SQL参数等，就可以访问数据库了，很方便。

在应用之前的配置文件设置数据库连接字符串，增加程序可移植性和代码的简洁。

</connectionStrings>
<appSettings>
<add key="ConnStr" value="Data Source=*;Initial Catalog=Charge;User ID=sa;Pwd=*"/>
</appSettings>

SQLHelper类

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration  '必须要在管理器中添加引用
''' <summary>
''' SqlHelper类是专门提供给广大用户用于高性能、可升级和最佳练习的sql数据操作
''' </summary>
''' <remarks></remarks>
Public Class SqlHelper
'定义变量
'获得数据库的连接字符串
Private ReadOnly strConnection As String = ConfigurationManager.AppSettings("ConnStr")
'设置连接
Dim conn As SqlConnection = New SqlConnection(strConnection)
'定义cmd命令
Dim cmd As New SqlCommand

''' <summary>
''' 执行增删改三个操作,(有参)返回值为Boolean类型,确认是否执行成功
''' </summary>
''' <param name="cmdText">需要执行语句,一般是Sql语句,也有存储过程</param>
''' <param name="cmdType">判断Sql语句的类型,一般都不是存储过程</param>
''' <param name="paras">参数数组,无法确认有多少参数</param>
''' <returns></returns>
''' <remarks></remarks>
Public Function ExecAddDelUpdate(ByVal cmdText As String, ByVal cmdType As CommandType, ByVal paras As SqlParameter()) As Integer
'将传入的值,分别为cmd的属性赋值
cmd.Parameters.AddRange(paras)   '将参数传入
cmd.CommandType = cmdType            '设置一个值,解释cmdText
cmd.Connection = conn                '设置连接,全局变量
cmd.CommandText = cmdText            '设置查询的语句

Try
conn.Open()                      '打开连接
Return cmd.ExecuteNonQuery()     '执行增删改操作
cmd.Parameters.Clear()           '清除参数
Catch ex As Exception
Return 0                         '如果出错,返回0
Finally
Call CloseConn(conn)
Call CloseCmd(cmd)
End Try
End Function
''' <summary>
''' 执行增删改三个操作,(无参)
''' </summary>
''' <param name="cmdText">需要执行语句,一般是Sql语句,也有存储过程</param>
''' <param name="cmdType">判断Sql语句的类型,一般都不是存储过程</param>
''' <returns>Interger,受影响的行数</returns>
''' <remarks>2013年2月2日8:19:59</remarks>
Public Function ExecAddDelUpdateNo(ByVal cmdText As String, ByVal cmdType As CommandType) As Integer
'为要执行的命令cmd赋值
cmd.CommandText = cmdText       '先是查询的sql语句
cmd.CommandType = cmdType       '设置Sql语句如何解释
cmd.Connection = conn           '设置连接

'执行操作
Try
conn.Open()
Return cmd.ExecuteNonQuery()
Catch ex As Exception
Return 0
Finally
Call CloseConn(conn)
Call CloseCmd(cmd)
End Try
End Function

''' <summary>
''' 执行查询的操作,(有参),参数不限
''' </summary>
''' <param name="cmdText">需要执行语句,一般是Sql语句,也有存储过程</param>
''' <param name="cmdType">判断Sql语句的类型,一般都不是存储过程</param>
''' <param name="paras">传入的参数</param>
''' <returns></returns>
''' <remarks></remarks>
Public Function ExecSelect(ByVal cmdText As String, ByVal cmdType As CommandType, ByVal paras As SqlParameter()) As DataTable

Dim sqlAdapter As SqlDataAdapter
Dim dt As New DataTable
Dim ds As New DataSet
'还是给cmd赋值
cmd.CommandText = cmdText
cmd.CommandType = cmdType
cmd.Connection = conn
cmd.Parameters.AddRange(paras)  '参数添加
sqlAdapter = New SqlDataAdapter(cmd)  '实例化adapter
Try
sqlAdapter.Fill(ds)           '用adapter将dataSet填充
dt = ds.Tables(0)             'datatable为dataSet的第一个表
cmd.Parameters.Clear()        '清除参数
Catch ex As Exception
MsgBox("查询失败", CType(vbOKOnly + MsgBoxStyle.Exclamation, MsgBoxStyle), "警告")
Finally                            '最后一定要销毁cmd
Call CloseCmd(cmd)
End Try
Return dt
End Function

''' <summary>
''' 执行查询的操作,(无参)
''' </summary>
''' <param name="cmdText">需要执行语句,一般是Sql语句,也有存储过程</param>
''' <param name="cmdType">判断Sql语句的类型,一般都不是存储过程</param>
''' <returns>dataTable,查询到的表格</returns>
''' <remarks></remarks>
Public Function ExecSelectNo(ByVal cmdText As String, ByVal cmdType As CommandType) As DataTable
Dim sqlAdapter As SqlDataAdapter
Dim ds As New DataSet
'还是给cmd赋值
cmd.CommandText = cmdText
cmd.CommandType = cmdType
cmd.Connection = conn
sqlAdapter = New SqlDataAdapter(cmd)  '实例化adapter
Try
sqlAdapter.Fill(ds)           '用adapter将dataSet填充
Return ds.Tables(0)             'datatable为dataSet的第一个表
Catch ex As Exception
Return Nothing
Finally                            '最后一定要销毁cmd
Call CloseCmd(cmd)
End Try
End Function

''' <summary>
''' 关闭连接
''' </summary>
''' <param name="conn">需要关闭的连接</param>
''' <remarks></remarks>
Public Sub CloseConn(ByVal conn As SqlConnection)
If (conn.State <> ConnectionState.Closed) Then  '如果没有关闭
conn.Close()                    '关闭连接
conn = Nothing                  '不指向原对象
End If

End Sub
''' <summary>
''' 关闭命令
''' </summary>
''' <param name="cmd">需要关闭的命令</param>
''' <remarks></remarks>
Public Sub CloseCmd(ByVal cmd As SqlCommand)

If Not IsNothing(cmd) Then          '如果cmd命令存在
cmd.Dispose()                   '销毁
cmd = Nothing
End If
End Sub
End Class