mybase（重温一下VB.net）

虽然VB.NET已经被微软停更了，但作为一门出色的编程语言，不当误事，还是很多人在使用。今天开始，重温一下VB.NET。

写点什么呢？才能假装很厉害的样子呢。

嗯，写个对数据库操作吧

那么让我们开始吧

首先，新建一个access数据库，创建表，设置好字段和对应的数据类型。

好了，现在打开VS软件，新建一个windows窗体应用项目，然后像我这样把控件摆放好。

给大家介绍一下，我在窗体上下放置了两个GroupBox容器，下面GroupBox上利用SplitContainer容器将区域分为三部分，左边放置listview控件，中间和右边放置两个PictureBox控件。

现在让我们开始码代码吧

首先双击窗体，开始添加Form1_Load代码:

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

Dim conn As New OleDbConnection

Dim cmd As New OleDbCommand

Dim reader As OleDbDataReader = Nothing

Dim lv As ListViewItem

Dim sql As String

sql = "select 编号,名称,时间 from 测试"

conn.ConnectionString = "provider=microsoft.ace.oledb.12.0;data source=C:UsersCYDesktop测试.accdb"

cmd.CommandText = sql

cmd.Connection = conn

Try

conn.Open()

reader = cmd.ExecuteReader

While reader.Read

lv = New listviewItem(reader.GetValue(0).ToString)

lv.SubItems.AddRange({reader.GetString(1), reader.GetDateTime(2)})

ListView1.Items.Add(lv)

End While

Catch ex As Exception

MessageBox.Show("出现异常" & ex.Message)

Finally

reader.Close()

conn.Close()

End Try

End Sub

下面开始添加新增数据功能，需要再新建一个窗体，激不激动现在有两个窗体了，摆好控件，像我这样，相关控件属性按自己喜好自行设置就好。

双击Form1中新增（Button3）按钮

进入Button3_Click（按钮点击事件），添加如下代码，就可以打开Form2（新增）窗体了。

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click

Form2.ShowDialog()

End Sub

然后就可以在Form2.vb里添加代码了，老样子双击Form2窗体，在Form2_Load中添加代码：

根据需要在class Form2内设置全局变量，因为会在其他事件里会用到。

Public Class Form2

Dim NumText As Integer

Dim i, j As Integer

Dim ImgNam1 As String

Dim ImgNam2 As String

Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load

Dim conn As New OleDbConnection

Dim cmd As New OleDbCommand()

Dim reader As OleDbDataReader

Dim sql As String

PictureBox1.Image = Nothing

PictureBox2.Image = Nothing

TextBox2.Text = ""

TextBox3.Text = ""

conn.ConnectionString = "provider=microsoft.ace.oledb.12.0;data source=C:UsersCYDesktop测试.accdb"

sql = "select MAX(编号) from 测试"

cmd.CommandText = sql

cmd.Connection = conn

reader = Nothing

Try

conn.Open()

reader = cmd.ExecuteReader()

If reader.Read Then

If reader.GetValue(0).ToString = "" Then

NumText = 0

Else

NumText = reader.GetValue(0)

End If

End If

Catch ex As Exception

MessageBox.Show("出现异常" & ex.Message)

Finally

reader.Close()

conn.Close()

End Try

TextBox1.Text = NumText + 1

这样就顺利自动生成编号了。

接下来我们要双击浏览（Button3）按钮，进入Button3_Click（按钮点击事件）为其添加代码：

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click

Dim ofd As New OpenFileDialog

ofd.Filter = "所有图片|*.png;*.jpg;*.gif"

If ofd.ShowDialog() = DialogResult.OK Then

i = i + 1

If i = 3 Then

i = 1

j = 1

End If

Else

Return

End If

If i = 1 Then

PictureBox1.Image = Image.FromFile(ofd.FileName)

TextBox3.Text = ofd.FileName

ImgNam1 = ofd.FileName

ElseIf i = 2 Then

PictureBox2.Image = Image.FromFile(ofd.FileName)

TextBox3.Text = ofd.FileName

ImgNam2 = ofd.FileName

End If

End Sub

完成上述代码的效果如下：

接下来我们要双击取消（Button2）按钮，进入Button2_Click（按钮点击事件）为其添加代码：

这个简单。

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click

Me.Close()

End Sub

然后就是双击保存（Button1）按钮，进入Button1_Click（按钮点击事件）为其添加代码：

Dim conn As New OleDbConnection

Dim cmd As New OleDbCommand()

Dim reader As OleDbDataReader

Dim TimText As String

Dim NamText As String

Dim sql As String

Dim RecordCount As Integer

Dim ms As New IO.MemoryStream

Dim ImgBuff() As Byte

TimText = Mid(DateTimePicker1.Value, 1, InStr(DateTimePicker1.Value, " ") - 1)

NamText = TextBox2.Text.Trim

If TextBox2.Text = "" Or TextBox3.Text = "" Or (i = 1 And j <> 1) Then

MessageBox.Show("取证信息填写不全")

Return

End If

conn.ConnectionString = "provider=microsoft.ace.oledb.12.0;data source=C:UsersCYDesktop测试.accdb"

sql = String.Format("insert into 测试 (编号,名称,图片1,图片2,时间) values({0},'{1}',@imgType1,@imgType2,'{2}')", NumText + 1, NamText, TimText)

cmd.CommandText = sql

cmd.Connection = conn

Try

conn.Open()

ImgBuff = My.Computer.FileSystem.ReadAllBytes(ImgNam1)

cmd.Parameters.Add("@imgType1", OleDbType.LongVarBinary)

cmd.Parameters("@imgType1").Value = ImgBuff

ImgBuff = My.Computer.FileSystem.ReadAllBytes(ImgNam2)

cmd.Parameters.Add("@imgType2", OleDbType.LongVarBinary)

cmd.Parameters("@imgType2").Value = ImgBuff

RecordCount = cmd.ExecuteNonQuery()

If RecordCount > 0 Then

sql = "select MAX(编号) from 测试"

cmd.CommandText = sql

reader = Nothing

Try

reader = cmd.ExecuteReader()

If reader.Read Then

NumText = reader.GetValue(0)

End If

Catch ex As Exception

MessageBox.Show("出现异常" & ex.Message)

Finally

reader.Close()

End Try

MessageBox.Show("新增信息完成")

TextBox1.Text = NumText + 1

TextBox2.Text = ""

TextBox3.Text = ""

End If

Catch ex As Exception

MessageBox.Show("出现异常" & ex.Message)

Finally

conn.Close()

End Try

PictureBox1.Image = Nothing

PictureBox2.Image = Nothing

i = 0

j = 0

End Sub

点击保存按钮，成功会弹出提示框：

再来看看数据库里有没有新增数据。

成功了。

当新增（Form2）窗体关闭时，我们要更新Form1中listview控件。这时候我们用到Form2的FormClosed事件，在Form2_FormClosed里添加代码：

Private Sub Form2_FormClosed(sender As Object, e As FormClosedEventArgs) Handles MyBase.FormClosed

Dim conn As New OleDbConnection

Dim cmd As New OleDbCommand()

Dim reader As OleDbDataReader

Dim sql As String

Dim lv As ListViewItem

i = 0

Form1.ListView1.Items.Clear()

conn.ConnectionString = "provider=microsoft.ace.oledb.12.0;data source=C:UsersCYDesktop测试.accdb"

sql = "select 编号,名称,时间 from 测试 order by 编号"

cmd.CommandText = sql

cmd.Connection = conn

reader = Nothing

Try

conn.Open()

reader = cmd.ExecuteReader()

While reader.Read

lv = New ListViewItem(reader.GetValue(0).ToString)

lv.SubItems.AddRange({reader.GetString(1), reader.GetDateTime(2)})

Form1.ListView1.Items.Add(lv)

End While

Catch ex As Exception

MessageBox.Show("出现异常" & ex.Message)

Finally

reader.Close()

conn.Close()

End Try

End Sub

下面我们要做的是当点击listview里的项时，显示图片。就要使用到listview中的SelectedIndexChanged事件，添加代码。

Private Sub ListView1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListView1.SelectedIndexChanged

Dim conn As New OleDbConnection

Dim cmd As New OleDbCommand()

Dim reader As OleDbDataReader

Dim sql As String

Dim Num As String

Dim ImgData1() As Byte = Nothing

Dim ImgData2() As Byte = Nothing

Dim ms As IO.MemoryStream

Dim Img As Image

If ListView1.SelectedItems.Count <> 0 Then

Num = ListView1.SelectedItems.Item(0).Text

conn.ConnectionString = "provider=microsoft.ace.oledb.12.0;data source=C:UsersCYDesktop测试.accdb"

sql = String.Format("select 图片1,图片2 from 测试 where 编号={0}", Num)

cmd.CommandText = sql

cmd.Connection = conn

reader = Nothing

Try

conn.Open()

reader = cmd.ExecuteReader()

If reader.Read Then

ImgData1 = reader(0)

ImgData2 = reader(1)

End If

ms = New IO.MemoryStream(ImgData1)

Img = Image.FromStream(ms)

PictureBox1.Image = Img

ms = New IO.MemoryStream(ImgData2)

Img = Image.FromStream(ms)

PictureBox2.Image = Img

ms.Close()

Catch ex As Exception

MessageBox.Show("出现异常" & ex.Message)

Finally

reader.Close()

conn.Close()

End Try

End If

End Sub

最终效果是这样的。