how to generate qr code in c# web application ADDING A VISUAL BASIC .NET EVENT HANDLER in Visual C#.NET

Drawer QR Code ISO/IEC18004 in Visual C#.NET ADDING A VISUAL BASIC .NET EVENT HANDLER

ADDING A VISUAL BASIC .NET EVENT HANDLER
Painting QR Code ISO/IEC18004 In C#.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create QR Code image in Visual Studio .NET applications.
www.OnBarcode.com
Scan QR Code 2d Barcode In C#
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
In Visual Basic. NET, you use two drop-down lists to define your events. This is a carryover from previous versions of Visual Basic. In the first drop-down list, you select an object on the page. The second drop-down list is then used to generate the event handler. The following steps walk you through this process. Here you add the event handler Page_Init.
Barcode Encoder In C#.NET
Using Barcode printer for .NET Control to generate, create bar code image in .NET framework applications.
www.OnBarcode.com
Bar Code Decoder In C#.NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
1. 2.
Quick Response Code Printer In Visual Studio .NET
Using Barcode creation for ASP.NET Control to generate, create QR Code 2d barcode image in ASP.NET applications.
www.OnBarcode.com
QR Code Generation In .NET Framework
Using Barcode generator for .NET Control to generate, create QR Code image in .NET applications.
www.OnBarcode.com
Inside the Visual Studio Solution Explorer, right-click a webpage and select View Code. This opens the code-behind file without inserting any code. In the code-behind file, select the object drop-down list from the upper-left part of the page and click Page Events, as shown in Figure 3-2.
Make Quick Response Code In Visual Basic .NET
Using Barcode creation for .NET framework Control to generate, create QR Code 2d barcode image in VS .NET applications.
www.OnBarcode.com
Generate Barcode In C#.NET
Using Barcode drawer for .NET Control to generate, create bar code image in VS .NET applications.
www.OnBarcode.com
Lesson 1: Understanding the ASP.NET Life Cycle and Handling Events
PDF-417 2d Barcode Generator In C#.NET
Using Barcode maker for .NET framework Control to generate, create PDF 417 image in VS .NET applications.
www.OnBarcode.com
Make UCC-128 In C#.NET
Using Barcode creation for VS .NET Control to generate, create EAN128 image in .NET framework applications.
www.OnBarcode.com
ChAPTER 3
Generate Code 39 In C#.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Code 39 Extended image in Visual Studio .NET applications.
www.OnBarcode.com
Make Leitcode In C#
Using Barcode encoder for VS .NET Control to generate, create Leitcode image in VS .NET applications.
www.OnBarcode.com
FigURE 3-2 Selecting the object that contains the event you want to handle.
Decoding GS1 - 12 In Visual C#
Using Barcode scanner for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Barcode Printer In .NET
Using Barcode creator for .NET framework Control to generate, create bar code image in .NET framework applications.
www.OnBarcode.com
Select the event drop-down list from the upper-right part of the page. Notice that all the events for the page are listed. Those events that are already handled on the page are listed in bold. Select the Init event, as shown in Figure 3-3.
Creating Bar Code In None
Using Barcode generator for Font Control to generate, create bar code image in Font applications.
www.OnBarcode.com
Bar Code Drawer In VS .NET
Using Barcode generation for Reporting Service Control to generate, create barcode image in Reporting Service applications.
www.OnBarcode.com
FigURE 3-3 Selecting the Init event handler for a Visual Basic. NET webpage.
Recognizing Denso QR Bar Code In None
Using Barcode reader for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Generating Code 39 In .NET Framework
Using Barcode printer for Visual Studio .NET Control to generate, create Code 39 Extended image in .NET framework applications.
www.OnBarcode.com
ChAPTER 3
Encoding European Article Number 13 In Java
Using Barcode drawer for Java Control to generate, create UPC - 13 image in Java applications.
www.OnBarcode.com
UPCA Generator In VB.NET
Using Barcode encoder for VS .NET Control to generate, create UPCA image in .NET applications.
www.OnBarcode.com
Handling Events and Managing State
Next, Visual Studio generates the following event stub for you. You can then add code inside this event that will be executed when this event is fired.
Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) _ Handles Me.Init End Sub
ADDING A C# EVENT HANDLER
The code editor for C# also has an event handler drop-down list. However, it only contains access to events you have already provided handlers for. The C# environment provides a tool for wiring up control events, but it does not provide such a tool for the Page events. For these, you have to code the event handler manually. Follow these steps to add the Init event handler to a C# webpage:
Right-click a webpage from Solution Explorer and choose View Markup to open the design code (HTML) for a page. Verify that the page s AutoEventWireup property is set to true in the @ Page directive (this is the default). This simply means that the runtime will automatically connect the event handlers it finds in your code that match the common form of Page_EventName. page s code-behind file loaded. From within the partial class brackets, add the handler code as shown in the following code block. This code will automatically be connected to the page s Init event at compile time.
private void Page_Init(object sender, EventArgs e) { }
2. Next, right-click the same page and click View Code to open the code editor with the
Handling events issued from individual controls in C# is a little easier. You are not required to recall the signature of each event. Instead, you can use the Property window for a control to generate an event stub in your code-behind file. The following procedure walks you through defining a Click event for a Button control.
1. 2. 3. 4.
Open a page in Design view. From the Toolbox, add a Button control to the page. Select the Button control and view its properties (right-click and select Properties). In the Properties window, click the Events icon (the yellow lightning bolt). This changes the Properties window to the events view. Figure 3-4 shows an example. From here, you locate the event you want to handle and double-click it in the Properties window. This will open the code-behind page and insert the event handler stub code.
Lesson 1: Understanding the ASP.NET Life Cycle and Handling Events
ChAPTER 3
FigURE 3-4 Adding an event handler to a C# server control.
Controlling Automatic Postback
Some web server controls always cause a postback when a specific event occurs. For example, the Button control s Click event always causes the browser to submit the form to the web server, initiating a postback. However, if a user selects a choice on a DropDownList, it does not post back to the server by default. For instance, the TextBox contains a default event called TextChanged. By default, the TextChanged event does not cause an automatic postback, so nothing happens on the server the moment the user changes text. The event is not lost, however. Instead, ASP.NET raises the event during the next postback, which usually occurs when the user clicks a button. When working with controls that have events that do not cause automatic postbacks to the server, it is important to understand when these events are raised. Recall the webpage life cycle defined in Table 3-1. Any postponed event (an event triggered by a user that does not cause an automatic postback) executes before the actual event that caused the postback. For example, if the text is changed in a TextBox and a Button is clicked, the Button click causes a postback, but the TextChanged event of the TextBox executes and then the Click event of the Button executes. The AutoPostBack property for a control is used to change whether that control s default event causes an automatic postback to the server. Set AutoPostBack to true to turn a postponed event to one that causes an immediate postback. You can do so in the Properties window, by using code, or by adding the AutoPostBack= True attribute to the web server control element in Source view. Figure 3-5 shows how to set AutoPostBack to true for a check box by using the Properties window. If the user were to change the state of that check box, the results would immediately be sent to the server.
Copyright © OnBarcode.com . All rights reserved.