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News Checker Description

Features | Detailed Description

Available in VCL and ActiveX editions.

The News Checker component allows you to check whether the specified resource is relatively up-to-date to the previously downloaded and to download a new one if it is necessary. The process of checking, downloading and displaying can be customized by defining the events sequence. By default, News Checker checks the following resource parameters (which are expected to be received in the HTTP resource header): resource size and resource date.

You may use this component for implementing online update of your software, online data replication and many other purposes.
Please see the How to implement automatic asynchronous data exchange in the company article to learn more about using this component.

Please see the Demos code (MultiDownLoader) and also the indexed Help documentation provided with the Clever Internet Suite installation for more details about using this component.

The most common members of the News Checker component can be seen below:

Property List

   Name    Description
 DataStream Defines the data stream to which the downloaded resource is saved.
 Errors Contains a list of errors for the internet control.
 IsNewsExists Specifies whether any of the updated news resource can be downloaded.
 LocalFile Specifies the file name, to which the downloaded resource is saved.
 Password Specifies the password that allows a control to log on to the server.
 Priority Determines the resource processing scheduling priority relative to other processes.
 HttpProxySettings Specifies the name of HTTP proxy server(s) to use when access via proxy is specified.
 FtpProxySettings Specifies the name of FTP proxy server(s) to use when access via proxy is specified.
 URL Specifies the Uniform Resource Locator (URL), from which the resource should be downloaded.
 UserName Specifies the user name that allows a control to log on to the server.

Method List

   Name    Description
 Start Starts the news checking process.
 Stop Stops the news downloading.

Event List

   Name    Description
 OnNewsExists Occurs immediately when a resource is really up-to-date and is successfully downloaded to the local computer.
 OnIsNews Occurs on downloading the news resource. Write this event handler to redefine the algorithm which is used to determine whether the downloaded resource is up-to-date.

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