To be able to open a file and read the data from a storage unit of a computer, such as a hard drive and able to save the data into the storage unit are important functions of a computer program. In fact, the ability to store, retrieve and modify data makes a computer a powerful tool in database management.
In this lesson, we will learn how to manage data that is stored as a text file. Visual Basic allows the user to create a text file, save the text file as well as read the text file.
Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services. Privacy policy. The ReadAllText method of the My. FileSystem object allows you to read from a text file. If you are reading from a file with extended characters, you will need to specify the file encoding.
FileSystem object. You can use the ReadLine method of the StreamReader object to read a file one line at a time. The file contains records of the structure Person.
This code example opens the file in Output mode; any process can read or write to file. This code example opens the file in Binary mode for reading; other processes cannot read file. The FileOpen function is provided for backward compatibility and may affect performance. For non-legacy applications, the My. FileSystem object provides better performance. For more information, see File Access with Visual Basic. When writing to a file, an application may have to create a file, if the file to which it is trying to write does not exist.
To do so, it needs permission for the directory in which the file is to be created. However, if the file specified by FileName does exist, the application needs Write permission only to the file itself. Wherever possible, to help improve security, create the file during deployment and grant Write permission to that file only, instead of to the whole directory. To help improve security, write data to user directories instead of to the root directory or the Program Files directory.
The following code excerpt further extends our example to read the data back from the file after it has been written and display the contents in a MessageBox:. A Visual Basic can monitor a file and receive notification from the operating system when the file is changed by any program. To try this, start Visual Studio and create a new Windows Application project. Access the Toolbox and double click on the FileSystemWatcher control from the Components section of the list.
The new object will appear beneath the Form design area with the name FileSystemWatcher1. Double click on the FileSystemWatcher1 object to access the event procedure code and modify the changed event as follows:. Press F5 to build and run the application and, using Notepad, edit and save the file. As soon as the changes are saved, the "File Changed" MessageBox will appear. Note that the NotifyFilter property can be used to configure which events trigger an notification.
Now that we have covered file handling in Visual Basic the next step is to look at directories in Working with Directories in Visual Basic.
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