嘗試使用VB.net從Acces資料庫訪問圖片檔案時，沒有為一個或多個必需引數指定值

我在做一個學校專案。我正在測驗我的應用程式的登錄表單。我正在嘗試與我的登錄表單和個人資料圖片表單分開。我已成功設法將影像保存到訪問資料庫，但在嘗試將其顯示在表單上的文本框中時遇到了很多問題。

這是整個應用程式代碼：

Imports System.Data.OleDb
Imports System.IO

Public Class Form2

    Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\geral\source\repos\BD de imagenes\BD de imagenes\DBImagenes.mdb")
    Dim cmd As New OleDbCommand
    Dim sql As String

    Dim da As New OleDb.OleDbDataAdapter
    Dim result As Integer

    Private Sub saveimage(sql As String)
        Try
            Dim arrimage() As Byte
            Dim mstream As New System.IO.MemoryStream
            PictureBox1.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Png)
            arrimage = mstream.GetBuffer()
            Dim Filesize As UInt32
            Filesize = mstream.Length
            mstream.Close()
            con.Open()
            cmd = New OleDbCommand
            With cmd
                .Connection = con
                .CommandText = sql
                .Parameters.AddWithValue("@Imagen", arrimage)
                .Parameters.Add("@Nombre", OleDbType.VarChar).Value = TextBox1.Text
                .ExecuteNonQuery()

            End With
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            con.Close()
        End Try
    End Sub

    'End Try

    Public conex As New OleDbConnection()
    Public Sub conexion()
        conex.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\geral\source\repos\BD de imagenes\BD de imagenes\DBImagenes.mdb"
        conex.Open()
    End Sub
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles BTNGuardar.Click
        sql = "Insert into TBImg (Imagen, Nombre) Values (@Imagen, @Nombre)"
        'sql = "Insert into TBImg (Imagen) Values (@Imagen)"
        saveimage(sql)
        MsgBox("Image has been saved in the database")
    End Sub

    Private Sub BtnExaminar_Click(sender As Object, e As EventArgs) Handles BtnExaminar.Click
        OpenFileDialog1.Filter = "Imagenes JPG|*.jpg|Imagenes PNG|*.png"
        OpenFileDialog1.RestoreDirectory = True
        If OpenFileDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then
            PictureBox1.Image = Image.FromFile(OpenFileDialog1.FileName)

        End If
    End Sub

    Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged

    End Sub

    Private Sub PictureBox1_Click(sender As Object, e As EventArgs) Handles PictureBox1.Click
        Try
            With OpenFileDialog1

                'CHECK THE SELECTED FILE IF IT EXIST OTHERWISE THE DIALOG BOX WILL DISPLAY A WARNING.
                .CheckFileExists = True

                'CHECK THE SELECTED PATH IF IT EXIST OTHERWISE THE DIALOG BOX WILL DISPLAY A WARNING.
                .CheckPathExists = True

                'GET AND SET THE DEFAULT EXTENSION
                .DefaultExt = "jpg"

                'RETURN THE FILE LINKED TO THE LNK FILE
                .DereferenceLinks = True

                'SET THE FILE NAME TO EMPTY 
                .FileName = ""

                'FILTERING THE FILES
                .Filter = "(*.jpg)|*.jpg|(*.png)|*.png|(*.jpg)|*.jpg|All files|*.*"
                'SET THIS FOR ONE FILE SELECTION ONLY.
                .Multiselect = False

                'SET THIS TO PUT THE CURRENT FOLDER BACK TO WHERE IT HAS STARTED.
                .RestoreDirectory = True

                'SET THE TITLE OF THE DIALOG BOX.
                .Title = "Select a file to open"

                'ACCEPT ONLY THE VALID WIN32 FILE NAMES.
                .ValidateNames = True

                If .ShowDialog = DialogResult.OK Then
                    Try
                        PictureBox1.Image = Image.FromFile(OpenFileDialog1.FileName)
                    Catch fileException As Exception
                        Throw fileException
                    End Try
                End If

            End With
        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Exclamation, Me.Text)
        End Try

    End Sub

    Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        conexion()
        PictureBox1.SizeMode = PictureBoxSizeMode.StretchImage
    End Sub

    Private Sub Label1_Click(sender As Object, e As EventArgs) Handles Label1.Click

    End Sub

    Private Sub BtnBuscar_Click(sender As Object, e As EventArgs) Handles BtnBuscar.Click
        Dim arrimage() As Byte
        Dim conn As New OleDb.OleDbConnection
        Dim Myconnection As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\geral\source\repos\BD de imagenes\BD de imagenes\DBImagenes.mdb"
        conn.ConnectionString = Myconnection
        conn.Open()
        sql = "Select * from TBImg where Nombre=" & (TBBuscar.Text)

        Dim cmd As New OleDbCommand
        With cmd
            .Connection = conex
            .CommandText = sql
        End With
        Dim publictable As New DataTable
        Try
            da.SelectCommand = cmd
            da.Fill(publictable)
            TextBox1.Text = publictable.Rows(1).Item("Nombre").ToString
            arrimage = publictable.Rows(1).Item("Imagen")
            Dim mstream As New System.IO.MemoryStream(arrimage)
            PictureBox1.Image = Image.FromStream(mstream)
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            da.Dispose()
            conn.Close()
        End Try
    End Sub
End Class

相關部分位于 Private Sub BtnBuscar_Click。

我正在嘗試在文本框中搜索我保存影像的名稱。但我沒有成功，我得到的只是標題的錯誤。

這就是我的資料庫看起來像影像被保存為 ole 物件的方式

這是我得到的錯誤

我正在關注本教程https://www.youtube.com/watch?v=zFdjp39mfhQ

但他并沒有完全解釋如何使用：

TextBox1.Text = publictable.Rows(0).Item(1)
arrimage = publictable.Rows(0).Item(1)'

不知道是不是這個問題的原因。

指示。我的代碼看起來不同的原因是我正在嘗試查看是否可以使其正常作業。

我試圖尋找答案，人們建議我可能把表名或列名弄錯了，但我用 ctrl c 和 ctrl v 復制了它在表中的確切名稱。

我想要的是，當我在資料庫的列名中鍵入名稱時，它會將存盤為 ole 物件的指定圖片帶到我的表單應用程式上所需的圖片框中。

不用說，我對 vb.net 和 SQL、Access 的經驗并不多。我只是按照教程來完成專案。

uj5u.com熱心網友回復：

不要在類級別宣告連接或命令或資料讀取器。它們都需要呼叫它們的 Dispose 方法。Using即使有錯誤，塊也會有宣告、關閉和處理。流也需要使用塊。

默認值 OpenFiledialog

1. 多選為假
2. CheckFileExists 為真
3. CheckPathExists 為真
4. 取消參考鏈接為真
5. 驗證名稱為真
6. 檔案名是“”

除非您通過線路獲得報酬，否則沒有必要將這些值重置為其默認值。

我已提醒您的過濾器排除All Files. 你也有 jpg 出現了兩次。

我宣告了一個變數來保存PictureFormat影像檔案的檔案擴展名 ,以便您可以為ImageFormat.

當您從資料庫中檢索影像欄位時，它會以Object. 得到Byte()一個DirectCast應該作業。

Private PictureFormat As String

Private Sub PictureBox1_Click(sender As Object, e As EventArgs) Handles PictureBox1.Click
    FillPictureBoxFromFile()
End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles BTNGuardar.Click
    Try
        saveimage()
    Catch ex As Exception
        MessageBox.Show(ex.Message)
        Exit Sub
    End Try
    MsgBox("Image has been saved in the database")
End Sub

Private cnStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\geral\source\repos\BD de imagenes\BD de imagenes\DBImagenes.mdb"

Private Sub saveimage()
    Dim arrimage() As Byte
    Using mstream As New System.IO.MemoryStream
        If PictureFormat.ToLower = ".png" Then
            PictureBox1.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Png)
        ElseIf PictureFormat.ToLower = ".jpg" Then
            PictureBox1.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)
        End If
        arrimage = mstream.GetBuffer()
        Dim Filesize As Long
        Filesize = mstream.Length
    End Using
    Using con As New OleDbConnection(cnStr),
            cmd As New OleDbCommand("Insert into TBImg (Imagen, Nombre) Values (@Imagen, @Nombre)", con)
        With cmd
            .Parameters.Add("@Imagen", OleDbType.Binary).Value = arrimage
            .Parameters.Add("@Nombre", OleDbType.VarChar).Value = TextBox1.Text
            con.Open()
            .ExecuteNonQuery()
        End With
    End Using
End Sub

    Private Sub BtnExaminar_Click(sender As Object, e As EventArgs) Handles BtnExaminar.Click
    FillPictureBoxFromFile()
End Sub

Private Sub BtnBuscar_Click(sender As Object, e As EventArgs) Handles BtnBuscar.Click
    Dim dt As DataTable
    Try
        dt = GetDataByName(TBBuscar.Text)
    Catch ex As Exception
        MessageBox.Show(ex.Message)
        Exit Sub
    End Try
    TextBox1.Text = dt(0)("Nombre").ToString
    Dim arrimage = DirectCast(dt(0)("Imagen"), Byte())
    Dim mstream As New System.IO.MemoryStream(arrimage)
    PictureBox1.Image = Image.FromStream(mstream)
End Sub

Private Function GetDataByName(name As String) As DataTable
    Dim dt As New DataTable
    Using conn As New OleDb.OleDbConnection(cnStr),
            cmd As New OleDbCommand("Select * from TBImg where Nombre= @Buscar", conn)
        cmd.Parameters.Add("@Buscar", OleDbType.VarChar).Value = TBBuscar.Text
        conn.Open()
        Using reader = cmd.ExecuteReader
            dt.Load(reader)
        End Using
    End Using
    Return dt
End Function

Private Sub FillPictureBoxFromFile()
    With OpenFileDialog1
        .Filter = "(*.jpg)|*.jpg|(*.png)|*.png"
        .RestoreDirectory = True
        .Title = "Select a file to open"
        If .ShowDialog = DialogResult.OK Then
            PictureBox1.Image = Image.FromFile(OpenFileDialog1.FileName)
        End If
        PictureFormat = Path.GetExtension(OpenFileDialog1.FileName)
    End With
End Sub

標籤：sql 网络 图片 ms-access 数据检索

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