auto generate barcode vb net Copyright 2001 by McGraw-Hill, Inc. Click Here for Terms of Use. in .NET framework

Creation QR in .NET framework Copyright 2001 by McGraw-Hill, Inc. Click Here for Terms of Use.

Copyright 2001 by McGraw-Hill, Inc. Click Here for Terms of Use.
Recognizing QR Code In Visual Studio .NET
Using Barcode Control SDK for VS .NET Control to generate, create, read, scan barcode image in .NET framework applications.
QR Code JIS X 0510 Encoder In .NET
Using Barcode creator for Visual Studio .NET Control to generate, create Denso QR Bar Code image in .NET framework applications.
DATA FILES
QR Scanner In .NET Framework
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in .NET framework applications.
Bar Code Encoder In .NET
Using Barcode printer for .NET Control to generate, create bar code image in .NET framework applications.
[CHAP. 9
Barcode Recognizer In VS .NET
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET applications.
Encode QR-Code In Visual C#
Using Barcode creation for .NET Control to generate, create QR-Code image in VS .NET applications.
Fig. 9.1 Activating the Common Dialog Control
Printing QR Code ISO/IEC18004 In VS .NET
Using Barcode drawer for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
Paint QR In VB.NET
Using Barcode encoder for VS .NET Control to generate, create QR Code 2d barcode image in Visual Studio .NET applications.
Common Dialog Control Icon
Painting Code 128 In .NET Framework
Using Barcode generation for VS .NET Control to generate, create Code 128C image in .NET applications.
Barcode Encoder In Visual Studio .NET
Using Barcode creator for .NET Control to generate, create barcode image in Visual Studio .NET applications.
Fig. 9.2 The Toolbox, with the addition of the Common Dialog Control When developing a Visual Basic project that involves opening a file or saving a file, place the common dialog control within a form, as you would with any other control tool. Unlike most other control tools, however, the common dialog control does not appear within the form when the project is being executed. Therefore, it does not matter where it is placed within the form. Usually, it is located in some out-of-the-way corner where it will not interfere with other controls, as shown in Fig. 9.3.
UPC-A Supplement 5 Generator In Visual Studio .NET
Using Barcode generator for VS .NET Control to generate, create UPC Symbol image in Visual Studio .NET applications.
2 Of 5 Interleaved Drawer In VS .NET
Using Barcode creation for VS .NET Control to generate, create USS ITF 2/5 image in .NET applications.
CHAP. 9]
Make GS1 DataBar In Java
Using Barcode creation for Java Control to generate, create DataBar image in Java applications.
Barcode Maker In Java
Using Barcode creator for Eclipse BIRT Control to generate, create barcode image in BIRT reports applications.
DATA FILES
Reading Code 128 Code Set B In VB.NET
Using Barcode decoder for VS .NET Control to read, scan read, scan image in .NET framework applications.
Code 128 Scanner In Visual Studio .NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in VS .NET applications.
Fig. 9.3 The common dialog control allows an application to easily access existing files or save new files through its common dialog boxes. For example, to access an existing file (i.e., to open the file), simply add a statement similar to that shown below at the appropriate place.
Encoding Barcode In C#
Using Barcode encoder for .NET Control to generate, create bar code image in .NET applications.
Generate EAN128 In Visual Studio .NET
Using Barcode creation for Reporting Service Control to generate, create GS1-128 image in Reporting Service applications.
CommonDialog1.ShowOpen
Generate ANSI/AIM Code 39 In Objective-C
Using Barcode drawer for iPad Control to generate, create ANSI/AIM Code 39 image in iPad applications.
ECC200 Decoder In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
When this statement is encountered during program execution, a dialog box similar to that shown in Fig. 9.4 will appear. The user may then use this dialog box to access a file within the currently active folder, or may maneuver to another folder to access a file. The type of files (i.e., the extension) can be specified within the program by assigning an appropriate string to the CommonDialog1.Filter property; e.g.,
CommonDialog1.Filter = "Text files (*.txt)|*.txt"
(This particular string assignment restricts the display to text files, though this restriction can be overridden by clicking on the down-arrow at the end of the box labeled Files of type.)
Fig. 9.4 The File Open dialog box Similarly, to save a file with a specified name, add a statement such as
CommonDialog1.ShowSave
DATA FILES
[CHAP. 9
When the ShowSave statement is encountered, a dialog box resembling that shown in Fig. 9.5 will appear. The user may then use this dialog box to save a file within the currently active folder, or some other folder either above or below the currently active folder. The type of files (i.e., the extension) that can be saved is specified by assigning an appropriate string to the CommonDialog1.Filter property, as shown previously. The file type can be changed by clicking on the down-arrow at the end of the box labeled Save as type.
Fig. 9.5 The Save As dialog box The common dialog control also permits the display of dialog boxes that allow the user to specify printer settings, to select a font, or to select a color. These dialog boxes are not required for accessing or saving data files, though the Print dialog box, shown in Fig. 9.6, is used in many file-related applications. The Print dialog box is generated by including a statement resembling the following at the appropriate place within the code.
CommonDialog1.ShowPrint
Fig. 9.6 The Print dialog box
CHAP. 9]
DATA FILES
9.3 PROCESSING A DATA FILE All applications involving the use of data files are based upon the same overall sequence of events. Specifically, the following three tasks must be carried out. 1. 2. 3. Open the data file. Process the file, as required by the application. Close the file.
EXAMPLE 9.1
Here is a skeletal outline of a Visual Basic procedure that reads data from a sequential file.
Private Sub mnuOpen_Click() Dim OldFile As String, i As Integer CommonDialog1.ShowOpen OldFile = CommonDialog1.FileName Open OldFile For Input As #1 i = 0 Do Until EOF(1) . . . . . 'read each data item from the input file, then process the data item 'continue until an end-of-file (EOF) condition has been detected on channel #1 . . . . . i = i + 1 Loop Close #1 End Sub
The CommonDialog1.ShowOpen command generates the Open dialog box, as shown in Fig. 9.4. The file name entered in this dialog box is then assigned to the string variable OldFile. The Open statement specifies that the data file is a sequential input file (i.e., an input text file) associated with data channel #1. The Do Until loop then reads data from the input file and updates the data (the details of which are not shown). Each pass through the loop reads and updates one data item. Note that EOF is a library function that returns a True condition once an end-of-file condition has been detected. Hence, the looping action continues until an end-of-file condition is encountered on data channel #1. Finally, the Close statement closes the file associated with data channel #1.
Opening the data file associates a channel number (also called a file number) with a named data file. It also specifies certain information about the data file, such as the mode (Input, Output, Append, Random, or Binary), the access type (Read, Write, or ReadWrite) and any restrictions (Shared, Lock Read, Lock Write, or Lock ReadWrite). (Do not confuse opening a data file with the process of retrieving a data file via the Open dialog box, as described in the last section.) Processing the data file generally involves reading the data items, modifying the data items, displaying the data items, and then writing the modified data items. There are many variations of this theme, depending upon the particular application. Closing the data file is a formality that simply deactivates the conditions that were specified when the file was opened. Visual Basic automatically closes all data files at the end of program execution if Close statements are not explicitly included within the program. Good programming practice suggests, however, that all open data files be closed explicitly. A file can no longer be accessed after it is closed, unless it is later reopened. Note, however, that a file can be reopened in another mode, with another access type, etc., after it has been closed. Some applications require that a file be reopened after it has been closed, as, for example, to read a set of data items after the records have been created or modified by the same program.
Copyright © OnBarcode.com . All rights reserved.