Question

有人检查我的代码是否将图像插入到数据库中。我知道有一些错误但无法弄清楚。当我运行代码时它工作但是当我点击完成按钮它总是说NullReferenceException这里是我有什么

Imports MySql.Data.MySqlClient
Imports System.IO

Public Class adminreg

Dim con As MySqlConnection
Dim cmd As MySqlCommand
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim reader As MySqlDataReader
    Dim mstream As New System.IO.MemoryStream
    PictureBox1.Image.Save(mstream, System.Drawing.Imaging.ImageFormat.Jpeg)
    Dim arrImage() As Byte = mstream.GetBuffer()
    mstream.Close()

    con = New MySqlConnection
    con.ConnectionString = "server=localhost;userid=root;password=1234;database=dat"


    Try
        con.Open()
        Dim query As String

        query = "insert into dat.login (idlogin,user,password,name,position,ownpic) values ('" & id.Text & "','" & usertxt.Text & "','" & passtxt.Text & "','" & nmetxt.Text & "','" & postxt.Text & "',@ownpic)"
        cmd.Parameters.AddWithValue("@ownpic", arrImage)

        cmd = New MySqlCommand(query, con)
        reader = cmd.ExecuteReader

        MessageBox.Show("Data Saved")

        con.Close()
    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        con.Dispose()
    End Try

End Sub

Private Sub adminreg_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

End Sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
    OpenFileDialog1.Filter = "imahe lang (*.jpg, *.bmp, *.png) | *.jpg; *.bmp; *.png| all files (*.*) | *.*"
    If OpenFileDialog1.ShowDialog <> Windows.Forms.DialogResult.Cancel Then
        PictureBox1.Image = Image.FromFile(OpenFileDialog1.FileName)

    End If
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
    Login.Show()
    Me.Hide()
End Sub
End Class

任何建议都非常感谢谢谢......只是VB.net的初学者

Answer 1

Private Sub pbStudentImage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles pbStudentImage.Click, txtStudentImage.Enter, txtStudentImage.Click Try Dim fileOpener As OpenFileDialog = New OpenFileDialog() fileOpener.Filter = "Image files | *.jpg"



      If fileOpener.ShowDialog() = Windows.Forms.DialogResult.OK Then
           pbStudentImage.Image = Image.FromFile(fileOpener.FileName)
           txtStudentImage.Text = fileOpener.FileName
      End If
 Catch ex As Exception
      MsgBox(ex.ToString())
 End Try


End Sub

Private Sub btnSaveImage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSaveImage.Click
     Dim con As MySqlConnection = New MySqlConnection(ConString)
     Dim cmd As MySqlCommand
     Dim fs As FileStream
     Dim br As BinaryReader

 Try
      If txtFirstName.Text.Length > 0 And txtStudentImage.Text.Length > 0 Then
           Dim FileName As String = txtStudentImage.Text
           Dim ImageData() As Byte

           fs = New FileStream(FileName, FileMode.Open, FileAccess.Read)
           br = New BinaryReader(fs)
           ImageData = br.ReadBytes(CType(fs.Length, Integer))
           br.Close()
           fs.Close()

           Dim CmdString As String = "INSERT INTO Students(FirstName, LastName, Image, Address) VALUES(@FirstName, @LastName, @Image, @Address)"
           cmd = New MySqlCommand(CmdString, con)

           cmd.Parameters.Add("@FirstName", MySqlDbType.VarChar, 45)
           cmd.Parameters.Add("@LastName", MySqlDbType.VarChar, 45)
           cmd.Parameters.Add(";@Image", MySqlDbType.Blob)
           cmd.Parameters.Add("@Address", MySqlDbType.VarChar, 100)

           cmd.Parameters("@FirstName").Value = txtFirstName.Text
           cmd.Parameters("@LastName").Value = txtLastName.Text
           cmd.Parameters("@Image").Value = ImageData
           cmd.Parameters("@Address").Value = txtAddress.Text
           con.Open()
           Dim RowsAffected As Integer = cmd.ExecuteNonQuery()
           If (RowsAffected > 0) Then
                MsgBox("Image saved successfully!")
           End If
           con.Close()
      Else
           MsgBox("Incomplete data!", MsgBoxStyle.Critical, "")
      End If

 Catch ex As Exception
      MsgBox(ex.ToString())
 Finally
      If con.State = ConnectionState.Open Then
           con.Close()
      End If
 End Try


End Sub

Private Sub pbStudentImage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles pbStudentImage.Click, txtStudentImage.Enter, txtStudentImage.Click
     Try
          Dim fileOpener As OpenFileDialog = New OpenFileDialog()
          fileOpener.Filter = "Image files | *.jpg"

  If fileOpener.ShowDialog() = Windows.Forms.DialogResult.OK Then
       pbStudentImage.Image = Image.FromFile(fileOpener.FileName)
       txtStudentImage.Text = fileOpener.FileName
  End If


Catch ex As Exception
      MsgBox(ex.ToString())
 End Try

End Sub

Private Sub pbStudentImage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles pbStudentImage.Click, txtStudentImage.Enter, txtStudentImage.Click
     Try
          Dim fileOpener As OpenFileDialog = New OpenFileDialog()
          fileOpener.Filter = "Image files | *.jpg"

  If fileOpener.ShowDialog() = Windows.Forms.DialogResult.OK Then
       pbStudentImage.Image = Image.FromFile(fileOpener.FileName)
       txtStudentImage.Text = fileOpener.FileName
  End If


Catch ex As Exception
      MsgBox(ex.ToString())
 End Try

End Sub

Private Sub btnSaveImage_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSaveImage.Click
     Dim con As MySqlConnection = New MySqlConnection(ConString)
     Dim cmd As MySqlCommand
     Dim fs As FileStream
     Dim br As BinaryReader

If fileOpener.ShowDialog() = Windows.Forms.DialogResult.OK Then pbStudentImage.Image = Image.FromFile(fileOpener.FileName) txtStudentImage.Text = fileOpener.FileName End If Catch ex As Exception MsgBox(ex.ToString()) End Try

使用longblob数据类型在mysql数据库中插入图像

1 个答案: