你好我试着做一些任务，我有一个问题
当我点击创建新学生数据库时，我收到错误
'Binary Formatters for serialization
Imports System.Runtime.Serialization.Formatters.Binary
'File Input/Output object
Imports System.IO
'ADO OleDb objects
Imports System.Data.OleDb
Public Class frmStart
'DbOptions class instance
Dim persistedOptions As New DbOptions
'String object to hold the path and name of the database
Dim dbFile As String
Private Sub initialiseOptions()
Dim myFileStream As Stream
'Create a BinaryFormatter object to use in deserializing the serialised file
Dim deserializer As New BinaryFormatter()
If File.Exists("DatabaseOptions.bin") Then
'The file exists so create a file stream object to open the file for reading
myFileStream = File.OpenRead("DatabaseOptions.bin")
'Set the instance of the OptionsClass to equal the saved serialized file
'Note that the deserialized file is conveted to an OptionClass object using CType()
persistedOptions = CType(deserializer.Deserialize(myFileStream), DbOptions)
If (dbFile <> "") Then
'CLose the file stream object
myFileStream.Close()
'Set status bar text to display curent DB file name
tsLblDbName.Text = dbFile
Else
'The db file name is blank (database closed) Set status bar text to none
tsLblDbName.Text = "None Open"
End If
myFileStream.Close()
Else
'The options file doesn't exist (first time run) Set status bar text to none
tsLblDbName.Text = "None Open"
End If
End Sub
Private Sub saveCurrentOptions()
Try
persistedOptions.DatabaseName = dbFile
'Create a file stream object that will create the file named SavedOptions.bin
Dim myFileStream As Stream = File.Create("DatabaseOptions.bin")
'Create a BinaryFormatter object to use in creating the serialised file
Dim serializer As New BinaryFormatter()
'Create the serialized OptionClass file using the BinaryFormatter object
serializer.Serialize(myFileStream, persistedOptions)
'CLose the file stream object
myFileStream.Close()
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Sub
Public Function CreateNewStudentDatabase(ByVal DatabaseFullPath As String) As Boolean
Dim cat As New ADOX.Catalog() 'ADOX Catalog object.
Dim studentTable As New ADOX.Table 'ADOX Table object
Dim PkIndex As New ADOX.Index 'ADOX Index object (for defining the Primary Key)
Dim sCreateString As String 'Holds the OLEDB connection string
Dim success As Boolean 'Flag to indicate create table success or fail
Try
sCreateString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & DatabaseFullPath
'The Catalog Create method creates and opens a new ADO Connection using sCreateString
cat.Create(sCreateString)
'Add the columns and their definition to the Table Columns collection
With studentTable
.Name = "Students"
.Columns.Append("StudentID", ADOX.DataTypeEnum.adVarWChar, 5)
.Columns.Append("FirstName", ADOX.DataTypeEnum.adVarWChar, 40)
.Columns.Append("LastName", ADOX.DataTypeEnum.adVarWChar, 40)
.Columns.Append("Address", ADOX.DataTypeEnum.adVarWChar, 40)
.Columns.Append("Suburb", ADOX.DataTypeEnum.adVarWChar, 40)
.Columns.Append("State", ADOX.DataTypeEnum.adVarWChar, 3)
.Columns.Append("PostCode", ADOX.DataTypeEnum.adVarWChar, 6)
.Columns.Append("PhoneNumber", ADOX.DataTypeEnum.adVarWChar, 12)
End With
PkIndex.Name = "PrimaryKey" 'Set a name for the Index
PkIndex.PrimaryKey = True 'Define the Index as a primary key index
PkIndex.Columns.Append("StudentID") 'Set the StudentID column as the index
studentTable.Indexes.Append(PkIndex) 'Add the index to Indexes collection of the table
cat.Tables.Append(studentTable) 'Add the new studentTable to the Tables collection
success = True 'Flag a successful creation
Catch Excep As System.Runtime.InteropServices.COMException
success = False 'Flag a failed database creation
Finally
'Clean up.no longer required objects
studentTable = Nothing
PkIndex = Nothing
cat = Nothing
End Try
Return success 'Return true or false to indicate success or fail
End Function
Private Sub frmStart_Load(sender As Object, e As EventArgs) Handles MyBase.Load
initialiseOptions() 'Call sub to read saved options
End Sub
Private Sub mnuFile_Db_NewDb_Click(sender As Object, e As EventArgs) Handles mnuFile_Db_NewDb.Click, btnCreateNewDb.Click
Dim newFile As New SaveFileDialog 'Create a new SaveFileDialog object
' Set the properties on SaveFileDialog
newFile.CreatePrompt = False
newFile.OverwritePrompt = False
newFile.FileName = "New Database"
newFile.Filter = "Microsoft Access Files |*.accdb" 'filter files by the extension
newFile.AddExtension = True 'Add extension (.accdb) if omitted by user
'Set the initial path to My Documents folder
newFile.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
If newFile.ShowDialog() = DialogResult.OK Then
dbFile = newFile.FileName
'Call the function to create the new database
If (CreateNewStudentDatabase(dbFile)) Then
saveCurrentOptions() 'Call sub to update saved options
initialiseOptions() 'Call sub to read saved options
MessageBox.Show("New blank database " & dbFile & " has been created and is connected.", "Database Created", 0, MessageBoxIcon.Information)
Else
MessageBox.Show("Failed to create and connect to new Database file!")
End If
End If
End Sub
Private Sub mnuFile_Db_OpenDb_Click(sender As Object, e As EventArgs) Handles mnuFile_Db_OpenDb.Click, btnOpenExistingDb.Click
Dim openFile As New OpenFileDialog 'Create a new OpenFileDialog object
openFile.Filter = "Microsoft Access Files |*.accdb" 'Show only files with .accdb extension
'Set the initial directory to the My Documents folder
openFile.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
openFile.Multiselect = False 'Dissallow multiple file selection
If (openFile.ShowDialog() = Windows.Forms.DialogResult.OK) Then
dbFile = openFile.FileName
saveCurrentOptions() 'Call sub to update saved options
initialiseOptions() 'Call sub to read saved options
End If
End Sub
Private Sub mnuFile_Db_CloseDb_Click(sender As Object, e As EventArgs) Handles mnuFile_Db_CloseDb.Click
dbFile = ""
saveCurrentOptions()
tsLblDbName.Text = "None Open"
End Sub
Private Sub mnuFileExit_Click(sender As Object, e As EventArgs) Handles mnuFileExit.Click
Application.Exit()
End Sub
Private Sub frmStart_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
If (MessageBox.Show("Are you sure you want to exit this application?", "Confrim Exit", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.No) Then
e.Cancel = True
End If
End Sub
Private Sub btnViewCurrentDb_Click(sender As Object, e As EventArgs) Handles btnViewCurrentDb.Click
'Check that a database has been opened and stored in variable dbFile
If (dbFile <> "") Then
'Create the connection that will be passed over to the Students form
Dim connection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & dbFile)
'Create an SQL query to retrieve all student record
Dim strQuery As String = "SELECT * FROM Students ORDER BY StudentID;"
Try
'Create an instance of frmStudents and pass the connection to the constructor
Dim studentDbForm As New frmStudents(connection)
'Show form in modal state
studentDbForm.ShowDialog()
Catch ex As Exception 'Catch any exception that occurs
'display error on what most likely went wrong as well as the System error message
MessageBox.Show("Failed to connect to " & dbFile & vbNewLine &
"The file may have been moved or deleted. Open an existing database or create a new one." &
vbNewLine & "System Message:" & vbNewLine & ex.Message, "Database Connection Failed", 0, MessageBoxIcon.Exclamation)
End Try
Else
MessageBox.Show("Please open an existing database or create a new one.", "No Active Database ", 0, MessageBoxIcon.Information)
End If
End Sub
End Class