Restrict (Prevent) duplicate record insert in database on ASP.Net Button Click

Hi phonghue,

After insert is executed you can redirect to the same page.

Response.Redirect(Request.Url.AbsoluteUri);

Use this code and check.

Protected Sub Upload(ByVal sender As Object, ByVal e As EventArgs)
    Dim filename As String = Path.GetFileName(FileUpload1.PostedFile.FileName)
    Dim extension As String = Path.GetExtension(filename)
    Dim contentType As String = FileUpload1.PostedFile.ContentType
    ' Check file extension.
    If extension.ToLower() = ".pdf" Then
        Using fs As Stream = FileUpload1.PostedFile.InputStream
            Using br As BinaryReader = New BinaryReader(fs)
                Dim bytes As Byte() = br.ReadBytes(Convert.ToInt32(fs.Length))
                Dim connString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
 
                Using conn As SqlConnection = New SqlConnection(connString)
                    Dim query As String = "INSERT INTO tblFiles (Name, Contenttype, data) VALUES (@Name, @ContentType, @Data)"
                    Using cmd As SqlCommand = New SqlCommand(query)
                        cmd.Connection = conn
                        cmd.Parameters.Add("@Name", SqlDbType.VarChar).Value = filename
                        cmd.Parameters.Add("@ContentType", SqlDbType.VarChar).Value = contentType
                        cmd.Parameters.Add("@Data", SqlDbType.Binary).Value = bytes
                        conn.Open()
                        cmd.ExecuteNonQuery()
                        conn.Close()
                    End Using
                End Using
            End Using
        End Using
        lblMessage.Text = "File uploaded successfully."
        lblMessage.ForeColor = Color.Green
    Else
        lblMessage.Text = "Select only pdf file."
        lblMessage.ForeColor = Color.Red
    End If
    Response.Redirect(Request.Url.AbsoluteUri)
End Sub