我正在vb.net中创建一个程序，在创建一个用户之前，我想检查该记录是否已经存在。
这是我的密码：
Imports MySql.Data.MySqlClient
Public Class WindowsAdvancedStudyStartingForms
Dim FirstName As String = ""
Dim SecondName As String = ""
Dim FullName As String = ""
Dim StudentClassReal As String = ""
Dim StudentClassValue As String = ""
Dim Address As String = ""
Dim Username As String = ""
Dim Password As String = ""
Dim SuccessfulMessage As Integer = 0
'MySql
Dim ServerString As String = "Server=myServer;User ID=myID;Passwordmy=Password;Database=myDatabase;SSLMode=None"
Dim SQLConnection As MySqlConnection = New MySqlConnection
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
FirstName = AFirstNameTextBox.Text
SecondName = ASecondNameTextBox.Text
FullName = FirstName + " " + SecondName
StudentClassValue = ASelectClassComboBox.SelectedItem
Address = AAddressTextBox.Text
Username = AUsernameTextBox.Text
Password = APasswordTextBox.Text
If StudentClassValue = "Class IX" Then
StudentClassReal = 9
Else
MessageBox.Show("You have selected a Wrong Class", "Wrong Class", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
If FirstName = "" And FirstName.Count = 1 Then
MessageBox.Show("You didn't enter your First Name", "First Name", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
'Nothing
End If
If SecondName = "" Then
MessageBox.Show("You didn't enter your Second Name", "Second Name", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
'Nothing
End If
If Address = "" Then
MessageBox.Show("You didn't enter your Address", "Address", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
'Nothing
End If
If Username = "" Then
MessageBox.Show("You didn't enter your Username", "Username", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
'Nothing
End If
If Password = "" Then
MessageBox.Show("You didn't enter your Password", "Password", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
'Nothing
End If
If StudentClassReal = "9" Then
Dim StudentInformationVerification As Integer = MessageBox.Show("Are you sure that these are your information?" & vbCrLf & "I am " + FullName + ", and I study at Class " + StudentClassReal + ". I live in " + Address + ". My Advanced Windows Study Username is " + Username + ", and my password is " + Password, "Information Verification", MessageBoxButtons.YesNo, MessageBoxIcon.Question)
If StudentInformationVerification = DialogResult.Yes Then
Dim SQLStatement As String = "INSERT INTO people(FirstName, SecondName, Class, Address, Username, Password) VALUES('" & FirstName & "','" & SecondName & "', '" & StudentClassReal & "', '" & Address & "', '" & Username & "', '" & Password & "')"
SaveName(SQLStatement)
My.Computer.Registry.LocalMachine.SetValue("Study", "1")
SuccessfulMessage = 1
Me.Close()
End If
If StudentInformationVerification = DialogResult.No Then
End If
Else
'Nothing
End If
End Sub
'MYSQL Connection
Private Sub WindowsAdvancedStudyStartingForms_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim RegistryCheck As String = My.Computer.Registry.LocalMachine.GetValue("Study")
If RegistryCheck = 1 Then
LoginForm1.Show()
Me.Close()
End If
APasswordTextBox.UseSystemPasswordChar = True
SQLConnection:
SQLConnection.ConnectionString = ServerString
Try
If SQLConnection.State = ConnectionState.Closed Then
SQLConnection.Open()
If SuccessfulMessage = 0 Then
MessageBox.Show("Connected to Windows Advanced Study Database", "Connection to Database Passed", MessageBoxButtons.OK, MessageBoxIcon.Information)
End If
Else
SQLConnection.Close()
MessageBox.Show("Could not Connect to Windows Advanced Study Database", "Connection to Database Failed", MessageBoxButtons.RetryCancel, MessageBoxIcon.Error)
If DialogResult.Retry Then
GoTo SqlConnection
End If
If DialogResult.Cancel Then
Close()
End If
End If
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
Public Sub SaveName(ByRef SQLStatement As String)
Dim cmd As MySqlCommand = New MySqlCommand
With cmd
.CommandText = SQLStatement
.CommandType = CommandType.Text
.Connection = SQLConnection
.ExecuteNonQuery()
End With
MessageBox.Show("Welcome to Advanced Windows Studying", "Authentication Successful", MessageBoxButtons.OK, MessageBoxIcon.Information)
End Sub
End Class
1条答案
按热度按时间qjp7pelc1#
使用参数。启用“选项严格”。你不需要所有的昏暗的学生信息。您可以将连接字符串传递给mysqlconnection的构造函数。将验证代码移到各个控件的validat事件。查找如何取消事件，以便将焦点放在适当的控件上。可以将sql字符串和连接直接传递给连接构造函数。使用…endusing语句将确保对象被正确关闭和释放，即使有错误。这对于确保连接关闭非常重要。不要使用goto。这只适用于向后兼容的语言，不应在新代码中使用(在真正的应用程序中，密码永远不会以纯文本的形式存储，但这是另一天的主题。在sql语句中，您需要用反记号（`）环绕mysql和mysql保留字，这是波浪号（~）下面的字符，是mysql的带引号的标识符。实际上，为了安全起见，在所有的表名和列名后面加上勾号并没有什么坏处。我无法测试此代码，因为我没有您的数据库。