Since user controls can have their own methods and attributes, they can also have their own events. Through methods and properties, the user control responds to the webpageCode. However, when an event is used, it is opposite to the method and attribute. The user control notifies the webpage of some activities and then responds to the webpage code.
Sometimes, adding an event to a user control can solve the big problem. For example, if you log on to the user control, you can add a submission event to it. In this way, you can easily obtain the returned value, such as the user name and password (viewstate ). Of course, adding events to user controls is not that troublesome. Generally, you can define an event in the user control file and subscribe to the event on the host page (aspx. When the button is clicked and materials are submitted, an event is generated and a notification is published, so that the host page can receive information and process the event.
The following is a demonstration.
User Control Page code<% @ Control Language = "C #" autoeventwireup = "true" codebehind = "logincontrol. ascx. cs" inherits = "aspnetteach4.logincontrol" %>
User name:<ASP: textbox ID= "Txtloginname" Runat= "Server"> </ASP: textbox>
Password:<ASP: textbox ID= "Txtloginpwd" Runat= "Server" Textmode= "Password"> </ASP: textbox>
Asp: button id = "btnlogin" runat =" server " text = "button" onclick = "btnlogin_click" />
After the page is designed, create the custom object logineventcontrolargs class and add an eventmessage attribute to the class. This attribute is a read-only attribute used to return related user name and password information.
Event parameter codePublic ClassLogineventcontrolargs: eventargs
{
Public StringLoginname {Get; set ;} Public StringLoginpwd {Get; set ;}
Public StringEventmessage {
Get {
ReturnDatetime. Now. tostring () +
"Account :"+ Loginname +
"--- Password :"+ Loginpwd;
}
}
}
After custom event parameters are defined, we also need to delegate the event signature. You can add the delegate to any place you like, usually in the same namespace.
Post Code of the controlPublic Delegate VoidLogineventcontrolhandler (ObjectSender, logineventcontrolargs );
Public Partial ClassLogincontrol: system. Web. UI. usercontrol
{
// Define the event
Public EventLogineventcontrolhandler loginevent;
Protected VoidPage_load (ObjectSender, eventargs E)
{
}
Protected VoidBtnlogin_click (ObjectSender, eventargs E)
{
If(Loginevent! =Null){
Logineventcontrolargs ARGs =NewLogineventcontrolargs ();
Args. loginname = txtloginname. text;
Args. loginpwd = txtloginpwd. text;
Loginevent (This, ArgS );
}
}
}
Now we have a method for customizing events. Next we will use the page
Call page<Body>
<Form ID= "Form1" Runat= "Server">
<Div>
<ASP: Label ID= "Label1" Runat= "Server" Text= "Label"> </ASP: Label>
<Uc1: logincontrol Runat= "Server" Onloginevent= "Logincontrol_loginevent" ID= "Logincontrol" />
</Div>
</Form>
Post Code</Body>
Protected VoidLogincontrol_loginevent (ObjectSender, logineventcontrolargs ARGs)
{
If(ARGs. loginname ="Admin"& Amp; args. loginpwd ="123"){ This. Label1.text ="Login successful";
}
Running Effect}
Dynamically load user controls in programming mode
In actual development, this situation often occurs, requiring the system to dynamically load related user controls according to certain conditions.
Protected VoidPage_load (ObjectSender, eventargs E)
{
Logincontrol c = page. loadcontrol ("~ /Logincontrol. ascx")AsLogincontrol;
Placeholder1.controls. Add (C );
C. loginevent + = logincontrol_loginevent;
}
Protected VoidLogincontrol_loginevent (ObjectSender, logineventcontrolargs ARGs)
{
If(ARGs. loginname ="Admin"& Amp; args. loginpwd ="123"){
This. Label1.text ="Login successful";
}
}
We can see that the method for dynamically adding controls is basically the same as that for winform.
However, the generatedSource codeThe Control ID is different from the ID on ASP.
We sometimes need to control Js. js compilation causes some errors if this ID is generated. So we can do this.
<Script Type= "Text/JavaScript">
Alert (<% = label1.clientid %>. innerhtml );
</Script>
Display Effect:
Clientidmode attribute
In addition to the above hard encoding method, we also have more elegant methods.
ASPnet provides us with three generated IDs.
Interit
By default, all controls on the page use clientidmode with the value of inherit, which indicates that the control will apply to the same clientidmode as its parent control, that is, This value specifies that the control generates an id like its parent control.
StaticUse the original control naming method
Autoid
Use the default 3.5 Generation Method
Next we will go to the second part of ASP. NET data access
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