CPS613

VB .NET Techniques and References

Toronto Metropolitan University University

External Files

Table of Contents

Static Files: How to load files at compile time

Dynamic File I/O: How to access files at run time

Static Files: How to load files at compile time

Application Resources: images, music, videos, etc.

 In some applications you will want to imbed the contents of some external files directly into the compiled VB program. This will make your program run faster as no I/O will be required at run time, but will also increase the size of your dll file.

In .NET this is accomplished by turning each file into an application resource. Here are the steps to turn an external file into a project resource:

  1. Open the Resource Editor for the project:
    To do this, double-click on "My Project" in the Solution Explorer, and select Resources > General and then click on the link to "create or open assembly sources".

    Alternately, you could select "View all files in the Solution Explorer and this will show you all the files in the "My Project" folder including Resources.resx, which keeps the resources for the project. Double-clicking on this file also brings up the Resource Editor.

  2. Select the type of resource you are importing:
    Use the leftmost pulldown menu of the Resource Editor for this. This step will make sure that the next step finds the right type of file. Generally speaking this pulldown is used to show all the existing resources of a specific type.

  3. Add and name the file as a project resource:
    Using the second pulldown menu of the Resource Editor, select Add Resource > Add Existing File... and add your file. The other options also work. Once the file is added as a resource, you will see the name of that resource along with an icon indicating its type.
Once you have added all the resources you need, Build the project. The resources will now be imbedded in your application and will show up where appropriate. For example, if you have added an image resource that you want to add in a control, this is usually done with the property called "Image" or "BackgroundImage". When you click on the three dots of that property in the Property window, the resource you have created will be available as a project resource.

The resource can also be accessed programmatically by using the My.Resources Object.

Dynamic Files: How to access files at run time

Interactive I/O Controls and Components

 VB has an OpenFileDialog component and a SaveFileDialog component that are used to traverse through your directories to find the pathnames of files to open or save. To use one of these components, drag it into the controls area at the bottom of your design page. You will need to use almost all the properties of these controls. In particular, don't forget to set the Filter and DefaultExt to work with image files. The online help examples include a lot of code writing, but you can actually set these properties at design time which is a lot simpler.

To run one of these dialog boxes, use the ShowDialog method (just like for the options dialog box). This method will return the status of the ShowDialog operation. Return values are of type DialogResult which is an enumeration type that can be used in Select Case statements. If the operation was successful, the pathname of the selected file will be in the FileName property of the control.

Manipulating Directories

Here is how to in Visual Basic.

Parsing File Paths

 Here is how to parse a file path in Visual Basic.

Copying Files

 Here is how to copy a file in Visual Basic:

Writing Files

Once you have the right pathname for your files, you will need to perform file I/O with these pathnames. To do so, you must first create either a StreamReader or a StreamWriter object. For example, 

Imports System.IO 	' Don't forget this imports statement
Class Game
	...
	Dim sw As StreamWriter = New StreamWriter(SaveFileDialog1.FileName)
	sw.Write(stuff)
	sw.WriteLine(more stuff)
	sw.Close()

Reading Files

 Reading is similar to writing except that you may also parse the lines you read in to convert comma-delimited information into actual values. The following two methods assist you in this:

This page is maintained by Sophie Quigley (cps613@cs.torontomu.ca)
Last modified Wednesday, 13-Sep-2023 00:54:42 EDT