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Reading Text Files | Visual Basic 6 (VB6)A very common need when programming almost any application is the ability to read data from a text file. Fortunately VB. NET excels at this sort of thing. In the tutorial that follows we will show exactly how you can read through a text file, parse the information, and use it in your Visual Basic application. This can be combined with other articles on this site to handle storing and reading data. Processing Text Files for Input (Reading)A data file consists of records, which consist of fields.
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The file that will be used for all examples in this section is a simplified employee file, which consists of the following fields: Field. Data Type*Employee Name. String. Department Number. Integer. Job Title.
String. Hire Date. Date. Hourly Rate.
Single*Please note that the data types for these fields are the data types of the variables into which these fields will be stored. In the text file, all fields will be represented as a string of characters. Suppose there were five records in the file. A graphic representation of the file populated with the five data records follows (the field names are not stored in the file): Employee Name(Last Name first)Dept # Job Title. Hire Date. Hourly Rate.
ANDERSON,ANDY 1. 00. PROGRAMMER3/4/1. 99. BABCOCK,BILLY 1. 10.
SYSTEMS ANALYST2/1. CHEESEMAN,CHARLIE 1.
COMPUTER OPERATOR3/1/1. DUNCAN,DARLENE 2. RECEPTIONIST1. 0/1. EACHUS,ERNIE 3. 00. MAIL ROOM CLERK8/1.
There are two basic ways a file like this would typically come to you. The first way is in fixed- length format, where each field is stored in a fixed position. On each record, a particular field starts and ends in the same position and occupies the same amount of space. The second way is in delimited format, where the fields within each record are separated from each other by a delimiter character. Commonly used delimiter characters are the tab (ASCII value 9), the "pipe" (vertical bar character "|"), and the comma (","). The comma- delimited file is probably the most commonly used (it is also referred to a "csv" file, where "csv" stands for "comma separated values") – however, there are certain considerations for comma- delimted files that must be taken into account; fortunately VB has an easy way to address these considerations.
The basic way to process both fixed- length files and delimited files is to read the file one line (record) at a time into a string variable, and then use string- handling methods to "break up" the data in the record into separate variables, where each variable represents a field of the record. However, in the case of delimited files, care must be taken to ensure that the data itself does not contain the delimiter character (because if it does, and your program does not handle this, you will wind up with misaligned fields and end- of- file errors). If using the tab (ASCII value 9), or another rarely- used character such as the pipe ("|"), chances are good that the data fields do not contain one of these characters – however, in the case of the comma- delimited file, some data fields may very well contain a comma – in which case the field will be enclosed in quotes. To handle the case of a comma- delimited file that contains fields enclosed in quotes, using native . NET methods, you would have to do extra string parsing to process the data correctly – however, there is a function in the MS. VB namespace that handles this parsing automatically for you, making it relatively easy to process such a file.
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We will first look at examples that will process fixed- length files and delimited files using both the System. IO namespace techniques and the Microsoft. Visual. Basic techniques. We will then look at an example that can easily handle a challenge brought about by comma- delimited files which contain fields enclosed in quotes.
Example 1: Reading a Text File with Fixed- Length Fields. In this example, for each record (line) of the file, each field starts and ends in the same position and occupies the same amount of space.
Reading Text Files Microsoft® Windows® 2000 Scripting Guide. Listing 4.39 Reading a Text File Using the ReadLine Method. How to read a text file by using System.IO in Visual Basic 2005. Reading text files in Visual Basic 2005 or in Visual Basic.NET Opening and reading files for.
The content of the file is shown below, along with a column position guide (highlighted in yellow) shown above the records. From the example, it should be clear that the employee name occupies positions 1 through 2. First, let us introduce the new VB.
NET elements that will be used in this example. Location of the Input File. The input file ("employee_fixed.
Read and write text files with Visual Basic. from previous versions of Visual Basic. Line-by-line Reading a text file. traditional Visual Basic file. Reading a File in Visual Basic. The problem I'm having is reading in the file in such a way that only the names or only the salaries will be displayed in the. Reading from a OpenXml Excel file (2007 format; *.xlsx). VB.NET Code: Dim stream As FileStream = File.Open(filePath, FileMode.Open, FileAccess.Read) '1.
Debug subdirectory of your application directory. This is the directory where the executable version of your program is created and stored when you test or run your program from the development environment.
This subdirectory can be referenced as follows: My. Application. Info. Directory. Path. To refer to the input file with the full directory path, you concatenate a backslash ("\") along with the filename to the above reference: My. Application. Info. Directory. Path& "\employee_fixed.
Note: "My. Application. Info. Directory. Path" would be the equivalent of "App. Path" in pre- . NET versions of VB.) The File. Stream Class. The File.
Stream class is used to create an object that will reference the file that will be processed by the program. The syntax for declaring a File.
Stream object, as it will be used in the examples that follow, is: Dim variable As. New File. Stream(path, mode, access [,share])wherepathis a string that refers to the full path and filename of the file to be processed. As in the example above, you can use a reference like My. Application. Info.
Directory. Path & "\somefile. C: \Some. Directory\Some. File. dat". modeis an enumeration that specifies how the file should be open or created. The possible values are: File. Mode. Append. Opens the file if it exists and starts writing new data at the end of the file (preserving what is already there). If the file does not exist, it is created.
File. Mode. Create. Creates a new file; if the file already exists, it is overwritten. File. Mode. Create.
New. Creates a new file; if the file already exists, an exception is thrown. File. Mode. Open. Opens an existing file; if the file does not exist, an exception is thrown. File. Mode. Open. Or. Create. Opens a file if it exists, or creates a new file if it does not exist. File. Mode. Truncate. Opens an existing file and truncates it (i.
The possible values are: File. Access. Read. Data can be read from the file, but not written to it. File. Access. Read.
Write. Data can be read from and written to the file. File. Access. Write. Data can be written to the file, but not read from it. The possible values are: File.
Share. None. Other processes may neither read from nor write to the file. File. Share. Read. Write. Any process can read from or write to the file. File. Share. Write. Other processes may write to the file. File. Share. Read.
Other processes may read from the file. Sample declaration: Dim str. File. Name As. String= My. Application. Info.
Directory. Path& "\employee_fixed. Dim obj. FS As. New File. Stream(str. File. Name, File. Mode. Open, File. Access. Read)In the above declaration, the filename was established in a separate string variable, which was then used as the path argument to the File. Stream class. The resulting variable, obj.
FS, is a File. Stream object that refers to the file. If desired, you could skip the separate declaration for the filename and write the declaration like this: Dim obj. FS As. New File. Stream(My. Application. Info. Directory. Path& "\employee_fixed. File. Mode. Open, File.
Access. Read)The Stream. Reader Class. The Stream. Reader class is used to read a stream of characters. In the . NET framework, a stream, in general terms, is the flow of data from one location to another. In the case of these examples, a stream refers to the text file that will be processed by the sample programs. The syntax for declaring a Stream.
Reader object is: Dim variable As. New Stream. Reader(stream)wherestreamis an object representing the stream of characters to be read (in this case a text file). Sample declaration: Assuming the declaration of obj.
FS as described above, the declaration could be written as follows: Dim obj. SR As. New Stream. Reader(obj. FS)If desired, you could skip the separate declarations for the filename and File. Stream and write the declaration like this: Dim obj. SR As. New Stream.
Reader( _. New File. Stream(My. Application. Info. Directory. Path& "\employee_fixed.
File. Mode. Open, File. Access. Read))Commonly used methods of the Stream. Reader class are: Peek. Looks ahead to the next available character in the input stream without actually advancing to that next position. If no character is available, Peek returns - 1. This method is convenient to test for end- of- file.)Read. Reads the next character from the input stream.
Read. Line. Reads the next line of characters from the input stream into a string. Read. To. End. Reads the data from the current position in the input stream to the end of the stream into a string.
This method is often used to read the entire contents of a file.)Close. Closes the Stream. Reader and its associated File. Stream object. Code for sample program #1: The following code reads the fixed- length format file as described above, record by record, and writes a formatted line containing the data from each record on the console. Imports System. IO. Module Module. 1. Dim str. File. Name As.
String = My. Application. Info. Directory. Path _. Dim obj. FS As. New File. Stream(str. File.
Name, File. Mode. Open, File. Access. Read)Dim obj. SR As. New Stream. Reader(obj. FS). Dim str. Emp. Record As. String. Dim str. Emp. Name As.
String. Dim int. Dept. Nbr As. Integer. Dim str. Job. Title As. String. Dim dtm. Hire. Date As. Date. Dim sng. Hrly. Rate As. Single. Console. Write. Line("The records in the employee_fixed.
Console. Write. Line(""). Console. Write. Line("EMPLOYEE NAME".
Pad. Right(2. 0) _. Space(3) _. & "DEPT" _. Space(3) _. & "JOB TITLE". Pad. Right(2. 1) _. Space(3) _. & "HIRE DATE " _.
Space(3) _. & "HRLY RATE"). Console. Write. Line("- -- -- -- -- -- -- ". Pad. Right(2. 0) _.
Read From Text Files in Visual Basic. The Read. All. Text method of the My. Computer. File. System object allows you to read from a text file. The file encoding can be specified if the contents of the file use an encoding such as ASCII or UTF- 8. If you are reading from a file with extended characters, you will need to specify the file encoding. Note To read a file a single line of text at a time, use the Open. Text. File. Reader method of the My.
Computer. File. System object. The Open. Text. File.
Reader method returns a Stream. Reader object. You can use the Read. Line method of the Stream. Reader object to read a file one line at a time. You can test for the end of the file using the End.
Of. Stream method of the Stream.