VB.NET ASP.NET Binary File Random Read Source Code Example
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VB.NET ASP.NET Binary File Random Read Source Code Example
Purpose: – Illustrates using Binary File with Random Read in VB.NET ASP.NET.
Prerequistes:
- Install Visual Web Developer 2010
- Install SQL Server Express
- Download Northwind and Pubs Databases
- Attach Northwind Database to Databases in Sql Express
- Attach pubs Database to Databases in Sql Express
Notes:
- You can build your own library of syntax examples by using same web site over and over and just add new web forms to it.
Instructions:
- Use Visual Web Developer 2010
- Create new web site;
- Click File/New Web Site
- Select ASP.NET Website Template
- Select Visual Basic for Language
- name of Web Site could be VBNET_ASPNET_Syntax.
- Add New folder named "FileDirectory"
- Right-click project name in solution explorer;
- add new folder;
- name of folder could be: FileDirectory
- Add Web Form Named BinaryFileRandomRead to FileDirectory folder
- Right-click FileDirectory folder;
- add new item;
- Select Web Form
- Check place code behind in separate file
- Web Form name could be BinaryFileRandomRead
- Click on copy code in code below to copy code into web form BinaryFileRandomRead.aspx
- Click on copy code in second set of code below to copy code into code-behind BinaryFileRandomRead.aspx.vb
- Right-click on BinaryFileRandomRead.aspx in solution explorer and select view in browser
Step 1: Click on Copy Code to Cut-n-paste code into BinaryFileRandomRead.aspx
| XML | | copy code | | ? |
< %@ Page Language="VB" AutoEventWireup="false" CodeFile="BinaryFileReadRandom.aspx.vb" Inherits="FileDirectory_BinaryFileReadRandom" %> |
< !DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> |
<html xmlns="http://www.w3.org/1999/xhtml"> |
<head runat="server"> |
<title></title> |
</head> |
<body> |
<form id="form1" runat="server"> |
<div> |
<asp:gridview ID="GridView1" runat="server"> |
</asp:gridview> |
</div> |
</form> |
</body> |
</html> |
Step 2: Click on Copy Code to Cut-n-paste code into BinaryFileRandomRead.aspx.vb
| Visual Basic | | copy code | | ? |
Imports System |
Imports System.IO |
Imports System.Data |
' This example is from http://idealprogrammer.com |
' It shows how you can use a binary file to track errors and also trace program execution |
' The errors and trace msgs are hard-coded in this example for simplicity |
Partial Class FileDirectory_BinaryFileReadRandom |
Inherits System.Web.UI.Page |
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load |
Dim myErr As New Err |
'Find next available file number |
Dim file_num As Integer = FreeFile() |
'Open file in random mode so we can write the records |
FileOpen(file_num, "c:\Errors.log", OpenMode.Random, _ |
OpenAccess.ReadWrite, OpenShare.Shared, _ |
Len(myErr)) |
'Write the records - the errors and trace msgs are hard-coded for simplicity |
Try |
FilePut(file_num, New Err(1, "Fake Error: IO error", System.DateTime.Now)) |
FilePut(file_num, New Err(2, "Fake Error: Array out of Bounds", System.DateTime.Now)) |
FilePut(file_num, New Err(3, "Fake Error: Divide Exception", System.DateTime.Now)) |
FilePut(file_num, New Err(4, "Fake Trace Msg: Executed Page Load", System.DateTime.Now)) |
FilePut(file_num, New Err(5, "Fake Trace Msg: Executed DataBind", System.DateTime.Now)) |
FilePut(file_num, New Err(6, "Fake Trace Msg: Executed Function to Calc dates", System.DateTime.Now)) |
Catch fileException As FileNotFoundException |
FilePut(file_num, New Err(7, "File does not exist", System.DateTime.Now)) |
Catch formattingException As FormatException |
FilePut(file_num, New Err(8, "Invalid format", System.DateTime.Now)) |
End Try |
Dim Table1 As DataTable |
Table1 = New DataTable("Errors") |
'creating a table named Errors |
Dim Row1 As DataRow |
'declaring row for the table |
Dim ErrorID As DataColumn = New DataColumn("ErrorID") |
'declaring a column named EmployeeID |
ErrorID.DataType = System.Type.GetType("System.Int32") |
'setting the datatype for the column |
Table1.Columns.Add(ErrorID) |
'adding the column to table |
Dim ErrorDescription As DataColumn = New DataColumn("ErrorDescription") |
ErrorDescription.DataType = System.Type.GetType("System.String") |
Table1.Columns.Add(ErrorDescription) |
Dim ErrorDate As DataColumn = New DataColumn("ErrorDate") |
ErrorDate.DataType = System.Type.GetType("System.DateTime") |
Table1.Columns.Add(ErrorDate) |
'Read the records |
Dim myErr2 As ValueType = DirectCast(myErr, ValueType) |
For i = 6 To 1 Step -2 |
FileGet(file_num, myErr2, i) |
myErr = DirectCast(myErr2, Err) |
Row1 = Table1.NewRow() |
'declaring a new row |
Row1.Item("ErrorID") = myErr.ErrorID |
'filling the row with values. Item property is used to set the field value. |
Row1.Item("ErrorDescription") = myErr.ErrorDescription |
'filling the row with values. adding ErrorDescription |
Row1.Item("ErrorDate") = myErr.ErrorDate |
'filling the row with values. Item property is used to set the field value. |
Table1.Rows.Add(Row1) |
Next i |
' Close the file. |
Try |
FileClose(file_num) |
Catch ex As IOException |
System.Diagnostics.Debug.Write("Cannot close file") |
End Try |
GridView1.DataSource = Table1 |
GridView1.DataBind() |
End Sub |
End Class |
Public Structure Err |
Public ErrorID As Integer |
<vbfixedstring (100)> Public ErrorDescription As String |
</vbfixedstring><vbfixedstring (50)> Public ErrorDate As String |
Public Sub New(ByVal new_id As Integer, ByVal error_description As String, _ |
ByVal error_datetime As String) |
ErrorID = new_id |
ErrorDescription = error_description |
ErrorDate = error_datetime |
End Sub |
End Structure |
</vbfixedstring> |
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