我的标题中不断出现运行时错误“已经有一个打开的 DataReader 与此连接关联，必须先关闭它。解决这个问题并重新启动应用程序......”请帮我找到我缺少的东西..
这是一个用 visual basic 和 MySQL (Xampp) 编写的聊天应用程序...
我不是这方面的专业人士...
如果你能帮我找出我需要更正的地方，我会很高兴。非常感谢
Imports System.Security.Cryptography
Imports System.IO
Imports MySql.Data.MySqlClient
Module functions
Public frndusrname As String
Public connection As New MySqlConnection
Public tempcon As New MySqlConnection
Public msgsubject As String = String.Empty
Public imageString As String
Dim conString As String
Sub tempconopen()
tempcon.ConnectionString = conString
Try
tempcon.Open()
Catch ex As Exception
MsgBox(ex.Message & vbNewLine & "Check your internet and database connections." & vbNewLine & "App is closing.", MsgBoxStyle.Critical, "Database Unreachable")
Application.Exit()
End
End Try
End Sub
Sub set_con_string(host As String, port As String, user As String, password As String, dbname As String)
conString = "server=" + host + "; port=" + port + "; user id=" + user + "; password=" + password + "; database=" + dbname
End Sub
Sub Create_DB(host As String, port As String, user As String, password As String, dbName As String)
Dim conn As MySqlConnection
Dim strConn As String
Dim cmd As MySqlCommand
strConn = "Server =" + host + "; port=" + port + "; userid = " + user + "; password =" + password + ";"
strConn &= "Database = mysql; pooling=false;"
conn = New MySqlConnection(strConn)
cmd = New MySqlCommand("Create Database If Not exists " + dbName, conn)
Try
conn.Open()
Catch ex As Exception
MsgBox(ex.Message & vbNewLine & "Unable to connect to the host (" & host & ") on specified port (" & port & ") with given user (" & user & ") and password." & vbNewLine & "App is closing.", MsgBoxStyle.Critical, "Host Unreachable")
Application.Exit()
End
End Try
Try
cmd.ExecuteNonQuery()
Catch ex As Exception
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
Application.Exit()
End
Finally
conn.Close()
End Try
End Sub
Sub InitilizeDatabase()
Dim insertcommand As New MySqlCommand
insertcommand = New MySqlCommand("CREATE TABLE `tb_chat` (`id` int(11) NOT NULL,`chat` longtext NOT NULL) ENGINE=InnoDB DEFAULT CHARSET=latin1;", connection)
Try
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Table 'tb_chat' already exists") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
insertcommand = New MySqlCommand("CREATE TABLE `tb_pm` (`id` int(11) NOT NULL,`username` varchar(200) NOT NULL,`fromuser` varchar(200) NOT NULL,`subject` varchar(300) NOT NULL,`message` text NOT NULL,`isread` int(11) NOT NULL) ENGINE=InnoDB DEFAULT CHARSET=latin1;", connection)
Try
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Table 'tb_pm' already exists") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
insertcommand = New MySqlCommand("CREATE TABLE `tb_users` (`id` int(11) NOT NULL,`username` varchar(200) NOT NULL,`password` varchar(200) NOT NULL,`email` varchar(200) NOT NULL,`name` varchar(200) NOT NULL,`dp` longtext NOT NULL,`mobile` varchar(50) NOT NULL,`chatcolor` varchar(100) NOT NULL,`chatfont` varchar(100) NOT NULL,`chatfontsize` int(11) NOT NULL,`chatfontstyle` varchar(40) NOT NULL) ENGINE=InnoDB DEFAULT CHARSET=latin1;", connection)
Try
insertcommand.ExecuteNonQuery()
insertcommand = New MySqlCommand("INSERT INTO `tb_chat` (`id`, `chat`) VALUES (1, 'Welcome to ChatShat!');", connection)
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Table 'tb_users' already exists") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
insertcommand = New MySqlCommand("ALTER TABLE `tb_chat` ADD PRIMARY KEY (`id`);", connection)
Try
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Multiple primary key defined") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
insertcommand = New MySqlCommand("ALTER TABLE `tb_pm` ADD PRIMARY KEY (`id`);", connection)
Try
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Multiple primary key defined") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
insertcommand = New MySqlCommand("ALTER TABLE `tb_users` ADD PRIMARY KEY (`id`);", connection)
Try
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Multiple primary key defined") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
insertcommand = New MySqlCommand("ALTER TABLE `tb_pm` MODIFY `id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=6;", connection)
Try
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Multiple primary key defined") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
insertcommand = New MySqlCommand("ALTER TABLE `tb_users` MODIFY `id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=19;", connection)
Try
insertcommand.ExecuteNonQuery()
Catch ex As Exception
If (Not ex.Message = "Multiple primary key defined") Then
MsgBox(ex.Message, MsgBoxStyle.Critical, "Database Error")
End If
End Try
End Sub
Sub openconnection()
connection.ConnectionString = conString
Try
connection.Open()
Catch ex As Exception
MsgBox(ex.Message & vbNewLine & "Check your internet and database connections." & vbNewLine & "App is closing.", MsgBoxStyle.Critical, "Database Unreachable")
Application.Exit()
End
End Try
End Sub
Function md5encrypter(ByVal strPass As String) As String
'Credit goes to dreamincode.net
Dim hasher As New MD5CryptoServiceProvider
Dim passbytes As Byte() = New Byte(strPass.Length + 3) {}
Dim hashBytes As Byte()
For i As Integer = 0 To strPass.Length - 1
passbytes(i) = CByte(Asc(strPass(i)))
Next
passbytes(strPass.Length) = CByte(90)
passbytes(strPass.Length + 1) = CByte(85)
passbytes(strPass.Length + 2) = CByte(66)
passbytes(strPass.Length + 3) = CByte(73)
hashBytes = hasher.ComputeHash(passbytes)
Dim newhashBytes As Byte() = New Byte(hashBytes.Length + 3) {}
For j As Integer = 0 To hashBytes.Length - 1
newhashBytes(j) = hashBytes(j)
Next
newhashBytes(hashBytes.Length) = CByte(90)
newhashBytes(hashBytes.Length + 1) = CByte(85)
newhashBytes(hashBytes.Length + 2) = CByte(66)
newhashBytes(hashBytes.Length + 3) = CByte(73)
strPass = Convert.ToBase64String(newhashBytes)
Return strPass
End Function
Function imgtobytes(ByVal imgPath As String) As String
Try
Dim dp_image As Image = Image.FromFile(imgPath)
Dim mems As MemoryStream = New MemoryStream()
dp_image.Save(mems, System.Drawing.Imaging.ImageFormat.Png)
Dim imgbytes As Byte() = mems.ToArray()
Dim strImg As String = Convert.ToBase64String(imgbytes)
Return strImg
Catch ex As Exception
MsgBox(ex.Message & vbNewLine & "Failed to convert image to bytes.", MsgBoxStyle.Critical, "Error Occurred")
End Try
Return String.Empty
End Function
End Module