在做机房收费系统中SQLHelper类的封装是必不可少的。我们先来看看SQLHelper到底是个什么东西 ?
SqlHelper是一个基于·NET Framework的数据库操作组件。组件中包含数据库操作方法。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。SqlHelpe组件中包含数据库操作方法，SqlHelper有很多版本，主要以微软一开始发布的SqlHelper类，后面包含进了Enterprise Library开源包中了。还有一个主要版本是dbhelper.org开源的sqlhelper组件，优点是简洁，高性能，不仅仅支持sqlserver，同时支持sqlserver、oracle、access、Mysql数据库，也是一个开源项目，提供免费下载。
下面是SQLHelper的一些简单方法封装。
代码：
Imports System.Data.SqlClient
''' <summary>
'''对数据库的查询，更新，删除数据操作
''' </summary>
''' <remarks>2013.12.20 by Gelupu</remarks>
Public Class SqlHelper
Dim strCon As String
Dim sqlCon As SqlConnection
Dim sqlCmd As SqlCommand
Dim dt As DataTable
Dim sqlApt As SqlDataAdapter
''' <summary>
''' 构造方法，初始化sqlCon
''' </summary>
''' <remarks></remarks>
Sub New()
'设置连接字符串
strCon = "Server=Gelupu-PC;Database=ChargeSys;User ID=sa;Password=123456"
'初始化sqlCon
sqlCon = New SqlConnection(strCon)
End Sub
''' <summary>
''' 打开数据库连接
''' </summary>
''' <remarks></remarks>
Public Sub OpenConnection()
sqlCon.Open()
End Sub
''' <summary>
''' 关闭数据库连接
''' </summary>
''' <remarks></remarks>
Public Sub CloseConnection()
sqlCon.Close()
sqlCon = Nothing
End Sub
''' <summary>
''' 执行不带参数的查询命令，返回数据表
''' </summary>
''' <param name="cmdText">SQL语句字符串</param>
''' <param name="cmdType">命令类型</param>
''' <returns>数据表</returns>
''' <remarks>2013.12.15 by Gelupu</remarks>
Public Function ExecuteQueryNoParameters(ByVal cmdText As String, ByVal cmdType As CommandType) As DataTable
'通过sqlCon数据库连接对象的CreatCommand方法创建一SqlCommand实例对象
sqlCmd = sqlCon.CreateCommand()
'给SqlCommand对象CommandText属性赋值
sqlCmd.CommandText = cmdText
'给SqlCommand对象CommandType属性赋值
sqlCmd.CommandType = cmdType
'实例化DataTable
dt = New DataTable
'实例化SqlDataAdapter
sqlApt = New SqlDataAdapter(sqlCmd)
Try
'打开数据库连接
Me.OpenConnection()
'执行命令,填充DataTable
sqlApt.Fill(dt)
'返回DataTable
Return dt
Catch ex As Exception
'返回错误信息
Return dt
Finally
'释放数据库操作对象
If Not IsNothing(sqlCmd) Then
sqlCmd.Dispose()
sqlCmd = Nothing
End If
'关闭数据库连接
If Not IsNothing(sqlCon) Then
Me.CloseConnection()
End If
End Try
End Function
''' <summary>
''' 执行带参数的查询命令，返回数据表
''' </summary>
''' <param name="cmdText">SQL查询语句字符串</param>
''' <param name="cmdType">命令类型</param>
''' <param name="Para">命令参数数组</param>
''' <returns>数据表</returns>
''' <remarks>2013/12/15 by Gelupu</remarks>
'''
Public Function ExecuteQueryWithParameters(ByVal cmdText As String, ByVal cmdType As CommandType, ByVal para() As SqlParameter) As DataTable
'通过sqlCon数据库连接对象的CreatCommand方法创建一SqlCommand实例对象
sqlCmd = sqlCon.CreateCommand()
'给SqlCommand对象CommandText属性赋值
sqlCmd.CommandText = cmdText
'给SqlCommand对象CommandType属性赋值
sqlCmd.CommandType = cmdType
'实例化DataTable
dt = New DataTable
'实例化SqlDataAdapter
sqlApt = New SqlDataAdapter(sqlCmd)
sqlCmd.Parameters.AddRange(para)
Try
'打开数据库连接
Me.OpenConnection()
'执行命令,填充DataTable
sqlApt.Fill(dt)
'返回DataTable
Return dt
Catch ex As Exception
'返回错误信息
Return dt
Finally
'释放数据库操作对象
If Not IsNothing(sqlCmd) Then
sqlCmd.Dispose()
sqlCmd = Nothing
End If
'关闭数据库连接
If Not IsNothing(sqlCon) Then
Me.CloseConnection()
End If
End Try
End Function
''' <summary>
''' 执行不带参数的增加，删除，修改命令，返回布尔值
''' </summary>
''' <param name="cmdText">SQL语句字符串</param>
''' <param name="cmdType">命令类型</param>
''' <returns>布尔值，标示命令是否执行成功</returns>
''' <remarks>2013.12.15 by Gelupu</remarks>
Public Function ExecuteNotQueryNoParameters(ByVal cmdText As String, ByVal cmdType As CommandType) As Boolean
'传入SQL语句和连接字符串，初始化SqlComm
sqlCmd = New SqlCommand(cmdText, sqlCon)
sqlCmd.CommandType = cmdType
Try
sqlCon.Open()
sqlCmd.ExecuteNonQuery()
Return True
Catch ex As Exception
Return False
Finally
'释放数据库操作对象资源
If Not IsNothing(sqlCmd) Then
sqlCmd.Dispose()
sqlCmd = Nothing
End If
'关闭数据库连接
If Not IsNothing(sqlCon) Then
Me.CloseConnection()
End If
End Try
End Function
''' <summary>
''' 执行带参数的数据库数据增加，删除，修改命令，返回布尔值
''' </summary>
''' <param name="cmdText">SQL语句字符串</param>
''' <param name="cmdType">命令类型</param>
''' <param name="para">命令参数数组</param>
''' <returns>布尔值，标示命令是否执行成功</returns>
''' <remarks>2013.12.15 by Gelupu</remarks>
Public Function ExecuteNotQueryWithParameters(ByVal cmdText As String, ByVal cmdType As CommandType, ByVal para() As SqlParameter) As Boolean
'传入SQL语句和连接字符串，初始化SqlComm
sqlCmd = New SqlCommand(cmdText, sqlCon)
'设置命令类型
sqlCmd.CommandType = cmdType
'给命令参数赋值
sqlCmd.Parameters.AddRange(para)
Try
'打开数据库连接
sqlCon.Open()
'执行命令，返回结果
'Return sqlCmd.ExecuteNonQuery()>0
sqlCmd.ExecuteNonQuery()
Return True
Catch ex As Exception
'返回失败
Return False
Finally
'释放数据库操作对象资源
If Not IsNothing(sqlCmd) Then
sqlCmd.Dispose()
sqlCmd = Nothing
End If
'关闭数据库连接
If Not IsNothing(sqlCon) Then
Me.CloseConnection()
End If
End Try
End Function
''' <summary>
''' 设置参数命令
''' </summary>
''' <param name="paramName">命令参数名称</param>
''' <param name="sqlType">命令参数的数据类型</param>
''' <param name="strValue">命令参数值</param>
''' <returns>命令参数数组</returns>
''' <remarks>2013.12.15 by Gelupu</remarks>
Public Function AddSqlParameter(ByVal paramName As String, ByVal sqlType As SqlDbType, ByVal strValue As String) As SqlParameter
'初始化命令参数
Dim sqlPara As New SqlParameter(paramName, sqlType)
'设置命令参数的值
sqlPara.Value = strValue
'返回命令参数
Return sqlPara
End Function
End Class
