Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click If Button2.Text = "保存" Then Button2.Text = "修改" End If End Sub Private Sub Button添加_Click(sender As Object, e As EventArgs) Handles Button添加.Click Button2.PerformClick() End Sub并不能成功修改button.text
时间: 2024-02-15 15:08:37 浏览: 31
这段代码存在一个问题,在`Button2_Click`事件中,当按钮文本为“保存”时,它会将按钮文本更改为“修改”,但没有实际修改任何内容。在`Button添加_Click`事件中,它调用了`Button2.PerformClick()`,但这并不会触发`Button2_Click`事件中的代码,因为按钮文本不是“保存”。
要解决这个问题,你需要在`Button2_Click`事件中添加实际的修改代码,例如:
```
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
If Button2.Text = "保存" Then
Button2.Text = "修改"
'执行保存操作
End If
End Sub
```
然后,在`Button添加_Click`事件中,你可以添加代码来将按钮文本更改为“保存”并触发`Button2_Click`事件:
```
Private Sub Button添加_Click(sender As Object, e As EventArgs) Handles Button添加.Click
Button2.Text = "保存"
Button2.PerformClick()
End Sub
```
这样,当你单击“添加”按钮时,它将会执行保存操作并将按钮文本更改为“修改”。
相关问题
Imports System.Data.OleDb Public Class Form3 Dim con As New OleDbConnection Dim adp As New OleDbDataAdapter Dim ds As New DataSet Private Sub Form3_Load(sender As Object, e As EventArgs) Handles MyBase.Load con.ConnectionString = "Provider=SQLOLEDB;Data Source=.;Integrated Security=SSPI;Initial Catalog=students" Dim selectcmd As New OleDbCommand selectcmd.CommandText = "select * from student" selectcmd.Connection = con adp.SelectCommand = selectcmd adp.Fill(ds, "Table") End Sub Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click For Each txt As TextBox In Me.Controls.OfType(Of TextBox)() txt.Text = "" Next For Each combo As ComboBox In Me.Controls.OfType(Of ComboBox)() combo.Text = "" Next End Sub Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click Dim insecmd As New OleDbCommand Dim Vs As String = TextBox1.Text & "','" & TextBox2.Text & "','" & ComboBox1.Text & "','" & ComboBox2.Text & "'," & TextBox3.Text & ",'" & ComboBox3.Text & ComboBox4.Text & ComboBox5.Text & "','" & TextBox4.Text & "','" & ComboBox6.Text & "','" & TextBox5.Text & "')" insecmd.CommandText = "insert into student values('" & Vs insecmd.Connection = con adp.InsertCommand = insecmd adp.Update(ds) End Sub End Class这段代码有什么问题
这段代码有几个问题:
1. 连接字符串是针对 SQL Server 的,而不是 Access 数据库。应该使用 Access 数据库的连接字符串,例如:
```
con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyDatabase.mdb"
```
2. 在插入数据时,字符串值应该使用参数化查询,而不是将值直接拼接到 SQL 语句中。这样可以避免 SQL 注入攻击,并且可以自动处理特殊字符的转义。应该改为类似下面的语句:
```
insecmd.CommandText = "insert into student values(?, ?, ?, ?, ?, ?, ?, ?, ?)"
insecmd.Parameters.AddWithValue("param1", TextBox1.Text)
insecmd.Parameters.AddWithValue("param2", TextBox2.Text)
'...
```
3. 在清空表单数据时,应该检查控件的类型是否为 TextBox 或 ComboBox,否则可能会出现异常。可以改为类似下面的语句:
```
For Each ctrl As Control In Me.Controls
If TypeOf ctrl Is TextBox Then
DirectCast(ctrl, TextBox).Text = ""
ElseIf TypeOf ctrl Is ComboBox Then
DirectCast(ctrl, ComboBox).Text = ""
End If
Next
```
4. 在插入数据后应该更新 DataSet 中的数据,以便在下一次查询中可以看到新插入的记录。可以改为类似下面的语句:
```
adp.Update(ds, "Table")
```
根据上述建议,可以将代码修改为:
```
Imports System.Data.OleDb
Public Class Form3
Dim con As New OleDbConnection
Dim adp As New OleDbDataAdapter
Dim ds As New DataSet
Private Sub Form3_Load(sender As Object, e As EventArgs) Handles MyBase.Load
con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyDatabase.mdb"
Dim selectcmd As New OleDbCommand
selectcmd.CommandText = "select * from student"
selectcmd.Connection = con
adp.SelectCommand = selectcmd
adp.Fill(ds, "Table")
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
For Each ctrl As Control In Me.Controls
If TypeOf ctrl Is TextBox Then
DirectCast(ctrl, TextBox).Text = ""
ElseIf TypeOf ctrl Is ComboBox Then
DirectCast(ctrl, ComboBox).Text = ""
End If
Next
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim insecmd As New OleDbCommand
insecmd.CommandText = "insert into student values(?, ?, ?, ?, ?, ?, ?, ?, ?)"
insecmd.Parameters.AddWithValue("param1", TextBox1.Text)
insecmd.Parameters.AddWithValue("param2", TextBox2.Text)
insecmd.Parameters.AddWithValue("param3", ComboBox1.Text)
insecmd.Parameters.AddWithValue("param4", ComboBox2.Text)
insecmd.Parameters.AddWithValue("param5", TextBox3.Text)
insecmd.Parameters.AddWithValue("param6", ComboBox3.Text & ComboBox4.Text & ComboBox5.Text)
insecmd.Parameters.AddWithValue("param7", TextBox4.Text)
insecmd.Parameters.AddWithValue("param8", ComboBox6.Text)
insecmd.Parameters.AddWithValue("param9", TextBox5.Text)
insecmd.Connection = con
adp.InsertCommand = insecmd
adp.Update(ds, "Table")
End Sub
End Class
```
Private Sub Button2_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button2.Click Dim comboBoxValue As String = ComboBox1.Text Dim filePath As String = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "abc.txt") If File.Exists(filePath) Then Dim existingText As String = File.ReadAllText(filePath) Dim lines() As String = existingText.Split(Environment.NewLine.ToCharArray(), StringSplitOptions.RemoveEmptyEntries) Dim updatedLines As New List(Of String)() ' 遍历每一行 For Each line As String In lines ' 检查行是否以ComboBox1的值开头 If Not line.StartsWith(comboBoxValue & ",") Then ' 不是匹配的行,将其添加到更新列表中 updatedLines.Add(line) End If Next File.WriteAllText(filePath, String.Join(Environment.NewLine, updatedLines)) MessageBox.Show("已成功删除文本文件中对应的行。") Else MessageBox.Show("文本文件不存在。") End If End Sub 修改以上代码的BUG
这段代码可能存在的问题是,如果文本文件中没有以ComboBox1的值开头的行,那么updatedLines列表将为空,而File.WriteAllText方法将写入一个空字符串到文件中,导致删除失败。可以通过添加一个条件语句来避免这个问题:
```
Private Sub Button2_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button2.Click
Dim comboBoxValue As String = ComboBox1.Text
Dim filePath As String = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "abc.txt")
If File.Exists(filePath) Then
Dim existingText As String = File.ReadAllText(filePath)
Dim lines() As String = existingText.Split(Environment.NewLine.ToCharArray(), StringSplitOptions.RemoveEmptyEntries)
Dim updatedLines As New List(Of String)()
For Each line As String In lines
If Not line.StartsWith(comboBoxValue & ",") Then
updatedLines.Add(line)
End If
Next
If updatedLines.Count > 0 Then ' 如果有匹配的行
File.WriteAllText(filePath, String.Join(Environment.NewLine, updatedLines))
MessageBox.Show("已成功删除文本文件中对应的行。")
Else ' 如果没有匹配的行
MessageBox.Show("没有找到要删除的行。")
End If
Else
MessageBox.Show("文本文件不存在。")
End If
End Sub
```