OleDb 异常未处理

Question

在运行此代码时，我似乎遇到了未处理的 OleDb 异常，我真的不明白为什么......

附上代码 谢谢！ 詹姆斯

Module DataAccess
    Private Builder As New OleDb.OleDbConnectionStringBuilder With
        {
            .Provider = "Microsoft.ACE.OLEDB.12.0",
            .DataSource = IO.Path.Combine(Application.StartupPath, "Database1.accdb")
        }
    ''' <summary>
    ''' Used to remove the current item selected in the txtFirstName text box.
    ''' </summary>
    ''' <param name="Name"></param>
    ''' <remarks></remarks>
    Public Sub RemmoveFemale(ByVal Name As String)
        Using cn As New OleDb.OleDbConnection With
                {
                    .ConnectionString = Builder.ConnectionString
                }
            Using cmd As New OleDb.OleDbCommand With {.Connection = cn}
                cmd.CommandText =
                    <SQL>
                        DELETE FROMCustomerNames WHERE CustomerName = @CustomerName
                    </SQL>.Value

                cmd.Parameters.Add(New OleDb.OleDbParameter With {.DbType = DbType.String, .ParameterName = "@CustomerName", .Value = Name})

                cn.Open()
                Dim Affected As Int32 = cmd.ExecuteNonQuery

            End Using
        End Using
    End Sub
    ''' <summary>
    ''' Called in Form1 on FormClosing event to update the database table if
    ''' needed.
    ''' </summary>
    ''' <param name="sender"></param>
    ''' <remarks></remarks>
    Public Sub UpdateFemaleNames(ByVal sender As AutoCompleteStringCollection)
        Dim NewNames As New List(Of String)

        Using cn As New OleDb.OleDbConnection With
                {
                    .ConnectionString = Builder.ConnectionString
                }
            Using cmd As New OleDb.OleDbCommand With {.Connection = cn}
                cmd.CommandText =
                    <SQL>
                        SELECT CustomerName
                        FROM CustomerNames
                        WHERE CustomerName = @CustomerName
                    </SQL>.Value

                cmd.Parameters.Add(New OleDb.OleDbParameter With {.DbType = DbType.String, .ParameterName = "@CustomerName"})

                cn.Open()

                For x As Int32 = 0 To sender.Count - 1
                    cmd.Parameters("@CustomerName").Value = sender.Item(x)
                    Dim Result As String = CStr(cmd.ExecuteScalar)
                    If String.IsNullOrWhiteSpace(Result) Then
                        NewNames.Add(sender.Item(x))
                    End If
                Next

                If NewNames.Count > 0 Then
                    cmd.CommandText =
                        <SQL>
                                INSERT INTO CustomerNames (CustomerName,Gender) VALUES (@CustomerNamee,@Gender)
                            </SQL>.Value

                    cmd.Parameters.Add(New OleDb.OleDbParameter With {.DbType = DbType.String, .ParameterName = "@Gender", .Value = "Female"})

                    For Each Item In NewNames
                        cmd.Parameters("@CustomerName").Value = Item
                        cmd.ExecuteReader()
                    Next

                End If

            End Using
        End Using
    End Sub
    ''' <summary>
    ''' Used in Form1 DataGridView1 for learning purposes only
    ''' </summary>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Function AllFemaleNames() As DataTable
        Dim dt As New DataTable
        Using cn As New OleDb.OleDbConnection With
                {
                    .ConnectionString = Builder.ConnectionString
                }
            Using cmd As New OleDb.OleDbCommand With {.Connection = cn}
                cmd.CommandText =
                    <SQL>
                        SELECT Identifier, CustomerName
                        FROM CustomerNames
                        WHERE Gender = 'Female'
                        ORDER BY CustomerName;
                    </SQL>.Value

                cn.Open()

                dt.Load(cmd.ExecuteReader)

            End Using
        End Using

        Return dt
    End Function
    ''' <summary>
    ''' Load only female first names into the auto complete source
    ''' </summary>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Function LoadFemaleNames() As AutoCompleteStringCollection
        Dim TheNameList As New AutoCompleteStringCollection


        Using cn As New OleDb.OleDbConnection With
                {
                    .ConnectionString = Builder.ConnectionString
                }
            Using cmd As New OleDb.OleDbCommand With {.Connection = cn}
                cmd.CommandText =
                    <SQL>
                        SELECT CustomerName
                        FROM CustomerNames
                        WHERE Gender = 'Female'
                        ORDER BY CustomerName;
                    </SQL>.Value

                cn.Open()
                Dim Reader As OleDb.OleDbDataReader = cmd.ExecuteReader

                If Reader.HasRows Then
                    While Reader.Read
                        TheNameList.Add(Reader.GetString(0))
                    End While

                    Reader.Close()

                End If

            End Using
        End Using

        Return TheNameList

    End Function

End Module








Module StringExtensions
    <Runtime.CompilerServices.Extension()> _
    Public Function ProperCase(ByVal sender As String) As String
        Dim TI As System.Globalization.TextInfo = New System.Globalization.CultureInfo("en-US", False).TextInfo
        Return TI.ToTitleCase(sender.ToLower)
    End Function
End Module







''' <summary>
''' Simple demo for auto complete adding items that are not in the list when pressing ENTER in TextBox1.
''' </summary>
''' <remarks></remarks>
Public Class Form1
    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
        UpdateFemaleNames(txtFirstName.AutoCompleteCustomSource)
    End Sub
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        txtFirstName.AutoCompleteMode = AutoCompleteMode.SuggestAppend
        txtFirstName.AutoCompleteSource = AutoCompleteSource.CustomSource
        txtFirstName.AutoCompleteCustomSource = LoadFemaleNames()
        ' The next two lines are for demo purposes only to see what is in the list for the TextBox with First names
        DataGridView1.DataSource = AllFemaleNames()
        DataGridView1.Columns("CustomerName").AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill
    End Sub
    Private Sub TextBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles txtFirstName.KeyDown
        If e.KeyCode = Keys.Enter Then
            If Not String.IsNullOrWhiteSpace(txtFirstName.Text) Then
                If Not txtFirstName.AutoCompleteCustomSource.Contains(txtFirstName.Text.ToLower) Then
                    txtFirstName.AutoCompleteCustomSource.Add(txtFirstName.Text.ProperCase)
                End If

                txtFirstName.Text = txtFirstName.Text.ProperCase

                e.SuppressKeyPress = True

            End If
        End If
    End Sub
    Private Sub cmdRemoveName_Click(sender As Object, e As EventArgs) Handles cmdRemoveName.Click
        If Not String.IsNullOrWhiteSpace(txtFirstName.Text) Then
            Dim CurrentName As String = txtFirstName.Text.Trim.ProperCase
            If My.Dialogs.Question(String.Format("Remove '{0}'", CurrentName)) Then
                RemmoveFemale(CurrentName)
                txtFirstName.AutoCompleteCustomSource.Remove(txtFirstName.Text)
                txtFirstName.Text = ""
            End If
        End If
    End Sub
End Class

Answer 1

如果没有确切的错误位置，就很难确定问题的根源。

但是，鉴于错误消息，您的一个或多个语句似乎包含未提供的参数。以下代码

If NewNames.Count > 0 Then
    cmd.CommandText =
        <SQL>
             INSERT INTO CustomerNames (CustomerName,Gender) VALUES (@CustomerNamee,@Gender)
        </SQL>.Value

    cmd.Parameters.Add(New OleDb.OleDbParameter With {.DbType = DbType.String, .ParameterName = "@Gender", .Value = "Female"})

    For Each Item In NewNames
        cmd.Parameters("@CustomerName").Value = Item
        cmd.ExecuteReader()
    Next

End If

客户参数的名称拼写为@CustomerNamee。调整这些或将 if 语句更改为类似

If NewNames.Count > 0 Then
    cmd.CommandText =
        <SQL>
             INSERT INTO CustomerNames (CustomerName,Gender) VALUES (@CustomerName,@Gender)
        </SQL>.Value

    For Each Item In NewNames
        cmd.Parameters("@CustomerName").Value = Item
        cmd.Parameters("@Gender").Value = "Female";
        cmd.ExecuteReader()
    Next
End If

Answer 2

从一开始，我就在您的代码中看到了这一行，这会导致该错误：

DELETE FROMCustomerNames WHERE CustomerName = @CustomerName

应该是这样的：

DELETE FROM CustomerNames WHERE CustomerName = @CustomerName

FROM 和 CustomerNames 之间没有空格

Answer 3

在您的 SQL 中：

SELECT CustomerName
FROM CustomerNames
WHERE Gender = 'Female'
ORDER BY CustomerName;

您引用了一个不存在的列。 Access 认为您正在要求一个参数，而您不是，因此您会收到您提到的错误。试试这个：

SELECT CustomerNames
FROM CustomerNames
WHERE Gender = 'Female'
ORDER BY CustomerNames;

用相同的名称命名字段和表或任何其他对象是个坏主意。这是有经验的，但你必须相信我。