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.NET Forum / ASP.NET / General / October 2007Web Parts Instances
I'm newish to web parts: Say for example I create a web part from a control that displays some text on a web page. The control would allow some text, which is stored in an sql database, to be edited. The user could in theory add several instances of this web part to a page, and each instance needs to display its unique text as stored in the corresponding record in the database. In order to achieve this I would imagine I need to tie a web part instance to some sort of unique identifier. How would I do this? In other words, how is it possible for different instances of the same web part to refer to unique records? Please tell me if I'm not making myself clear. JJ Ok I think, or rather hope, I've gone some way to answering my own question. I've used the controls UniqueID property to establish a connection between the instance an a unique record in the database. From my very limited tests, this UniqueID property doesn't seem to change if you change the position of the web part on the page, or if you add others around it, or change the order. My next quesiton is, is this uniqueID unique throughout the entire site, or do I need to add some other unique information to it (like the path to the current page, for instance)? I suspect I do, but would appreciate some advice here... JJ > I'm newish to web parts: > [quoted text clipped - 11 lines] > Please tell me if I'm not making myself clear. > JJ Hi JJ, To answer your question first, Yes, UniqueID is a unique identifer for a given control, but this is only guaranteed at page level(for this web form page), it help make sure that on the client-side rendered html form, every control won't have duplicated client identifiers. for your scenario, you just need to make sure each webpart control(of your custom one) instance has its own unique value and this value need to be automatically generated, correct? If so,I think you can consider the following approaches: 1) Use the Page's "GetHashCode" to get its instance identifier and then combine it with your control's uniqueID(or also HashCode value) to generate an new identifer. 2) You can use the current timestamp and combine your control's ID to generate an identifer How do you think? If there is anything I misunderstood, please feel free to post here. Sincerely, Steven Cheng Microsoft MSDN Online Support Lead ================================================== Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif ications. Note: The MSDN Managed Newsgroup support offering is for non-urgent issues where an initial response from the community or a Microsoft Support Engineer within 1 business day is acceptable. Please note that each follow up response may take approximately 2 business days as the support professional working with you may need further investigation to reach the most efficient resolution. The offering is not appropriate for situations that require urgent, real-time or phone-based interactions or complex project analysis and dump analysis issues. Issues of this nature are best handled working with a dedicated Microsoft Support Engineer by contacting Microsoft Customer Support Services (CSS) at http://msdn.microsoft.com/subscriptions/support/default.aspx. ================================================== This posting is provided "AS IS" with no warranties, and confers no rights. -------------------- >From: "JJ" <abc@xyz.com> >References: <O9U2W9dBIHA.4880@TK2MSFTNGP03.phx.gbl> [quoted text clipped - 30 lines] >> Please tell me if I'm not making myself clear. >> JJ Hi Steven. Your answer leads me onto some more questions: 1) Using the method of combining the pages 'GetHashCode' with the controls UniqueID: I can see how this would work - I could recalculate this value each time a control loads and then use this as a key to find the corresponding database record. My question is, however, does this GetHashCode algorythm change when the framework changes (I understand that .net 1.1 was different to .net 2.0)? Such a change would break the link between control and database record - a problem I belive some others had when upgrading to .net 2.0. 2) Using the current timestamp + control UniqueID: I can see how this would generate a new unique identifier each time the control was created - but how would I 'store' the original value in order to use it next time as a key to look up the database record? Surely it would change each time the control was loaded? There must be a technique here that is being used in personalization - i.e. the personalization 'system' knows which control/webpart is which and where its located on the page. Unfortunately, the tables do not reveal exactly how this is done. I look forward to your (or others) response, Many thanks, JJ > Hi JJ, > [quoted text clipped - 92 lines] >>> Please tell me if I'm not making myself clear. >>> JJ Another thougth about the GetHashCode + Unique ID method: In this scenario I am building a limited CMS system. It is possible therefore that the URL of the page may change if its location in changed in the heirachy of the site (which will use URL rewriting). Is the Hash Code based on this URL, or on some unchanging properties (like the filename and path from root, for example)? If its based on the re-written url, then this will change and so, again the connection between the unique identifier and the database record will be broken... Thanks, JJ > Hi JJ, > [quoted text clipped - 92 lines] >>> Please tell me if I'm not making myself clear. >>> JJ I'm really stuck here if anyone can help. I'm basically trying to create a html editor web part (not using Sharepoint). In order to do this I need to somehow hard wire the web part instance (remembering that there may be more than one instance of this web part on any page, and that the pages url may change also due to the cms/url rewriting) to a database record that stores the actual html. My problem seems to come down to: 1) how you would pick a unique identifier that could be used as a key to the database record, 2) how you would keep this constant whenever the web part was moved, page url changed (via url re-writing) etc, 3) how the unique identifier would persist (if it was not somehow calculated each time the web part loads) indefinately ?? Web parts seem to me to be an obvious approach to building a 'simple' cms, in that an 'editor' can add/remove parts via the shared scope. What I am trying to do here is create a part that also allows them to edit what text is within one of the parts. Judging by the lack of info around on this issue, I am either doing something that will never work, or I am missing something obvious.... Please help if you can, JJ > Another thougth about the GetHashCode + Unique ID method: > In this scenario I am building a limited CMS system. It is possible [quoted text clipped - 114 lines] >>>> Please tell me if I'm not making myself clear. >>>> JJ Thanks for your followup JJ, To answer the question in former messages: *Yes, GetHasCode implementation may vary between different framework version, it has opacity. *Sure, timestamp approach can only make sure you assign a new created instance a unique ID, it should be our own code logic to always associcate a given ID with a certain objecct instance(for your case, the object is Editor web part). In original messages, I haven't realized that you need to associate your editor webpart with database record. Would you provide some more business code logic info on this? Now, what I understand is that you may have multiple editor webpart instances on a page and each of them should map to a unique record in database. And next time user open page and open new editor webparts, you need to associate them to database records again,correct? If this is the case, I'm afraid it is quite hard to archive. Because generally, the mapping sequence should be as below: ** you retrieve records from database ** you create editor webparts based on those records in databases It's quite hard to create webparts and then associate them with database records. Because you haven't any identifer for those new created webparts, right? Mostly, in web application, you may consider using current user's identifer(if there is user authentication in your application) to uniquely identify an object. Do you think it is possible to do this in your application? Anyway, please feel free to let me know if there is still anything I missed here. Sincerely, Steven Cheng Microsoft MSDN Online Support Lead This posting is provided "AS IS" with no warranties, and confers no rights. -------------------- >Subject: Re: Web Parts Instances >Date: Thu, 4 Oct 2007 14:14:56 +0100 >I'm really stuck here if anyone can help. > [quoted text clipped - 75 lines] >>> >>> Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif >>> ications. >>> [quoted text clipped - 63 lines] >>>>> Please tell me if I'm not making myself clear. >>>>> JJ Dear Steven, Thanks for you response. In reply: Yes I do need to associate a web part instance with a specific database record. I find it hard to beleive this is not possible - how does personalisation know which web part is which when applying personalisation (shared scope) information held in database records? I have no code as yet as I have been trying to overcome this particular issue before continuing. The requirement is quite simple and I am sure others must have done this: I simply want a html editor web part that I can place (in shared scope) on a page, as many times as I wish. You can see how this would be a building block for a content management system. Currently, I use a html editor control (not using web parts), which uses a querystring parameter to identify the database record which holds the html. Clearly this is not the solution that should be applied with multiple instances of the same control/webpart. It would not be possible to use the current username as an identifier because: (1) we're talking about adding/moving/removing web parts for all users (shared scope); (2) I can't see how that would help in associating a particular web part instance with a particular database record. I could see how your suggestion with using the GetHashCode(page) + UniqueID(control) could be calculated consistently each time the web part loaded - i.e. use that as a key in the database record - however, when I upgrade framework I would probably lose all ties between the web part and the database record. That would be a real problem. Surely this can be done?? JJ > Thanks for your followup JJ, > [quoted text clipped - 209 lines] >>>>>> Please tell me if I'm not making myself clear. >>>>>> JJ Here's a small example of what I am trying to do. This site is based on web parts. You can add multiple instances of the same web part on a page and each web part accessed different database records. Go to this site: http://www.pageflakes.com/ And choose to Personalize your page. Now choose to add the 'Sticky Note' web part, then add another one. You can see that you can type different text in each web part and move the web parts around. Each web part is associated with a different record stored in the database. This is a simplified version of what I need. This surely proves that there is a way to do this. Yes, the page information is based on a per user basis, but you still have the problem of associating a particular web part with a particular database record for each user (i.e. using the username as a key to finding the record is not enough). ?? > Thanks for your followup JJ, > [quoted text clipped - 209 lines] >>>>>> Please tell me if I'm not making myself clear. >>>>>> JJ Better still they have a notepad 'pageflake' there (you need to 'Browse all flakes' when personalizing your page), and that is exactly what I am trying to create. > Here's a small example of what I am trying to do. This site is based on > web parts. You can add multiple instances of the same web part on a page [quoted text clipped - 239 lines] >>>>>>> Please tell me if I'm not making myself clear. >>>>>>> JJ Hi JJ, Yes, I have looked at the pageflake sites you provided, it seems a typical webpart like personalizable page. And we can drag multiple instances of StickyNote parts onto the page and type difference info into. However, when I close the page and visit it again, I think it should regenerate the page interface with database record. e.g. It will add two StickyNots parts onto page again, and assign their ID as the one from database record(rather than recalculate the ID via code), right? Also, for such personalize page, it will surely depend on client cookie, otherwise, the server won't know whether it is the same client that request the page again or which personalized data should retrieve from database to repopulate it. So cookie will play an important role here, do you think so? Sincerely, Steven Cheng Microsoft MSDN Online Support Lead This posting is provided "AS IS" with no warranties, and confers no rights. -------------------- >From: "JJ" <abc@xyz.com> >Subject: Re: Web Parts Instances >Date: Fri, 5 Oct 2007 13:57:23 +0100 >Better still they have a notepad 'pageflake' there (you need to 'Browse all >flakes' when personalizing your page), and that is exactly what I am trying [quoted text clipped - 164 lines] >>>>>> >>>>>> Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif >>>>>> ications. >>>>>> [quoted text clipped - 73 lines] >>>>>>>> Please tell me if I'm not making myself clear. >>>>>>>> JJ Hi Steven, Yes, the site does regenerate the stickies etc (otherwise there would be no point in the site having such features), but you have to register in order for your personalization to be saved. The 'cookie' may play an important role in identifying a user (anonymous or otherwise) but I do not see how it relates to how the webparts recalculate their corresponding database record upon reload (even once the user is identified). I am sure you trying to hint to me how it is done, but I'd appreciate a bit more information because I still do not understand? Are you saying that Unique Identifier = pageURL(unique on the site) + userid(unique to the user) + controlID(unique on the page), will do the job? I guess that then I would have to re-establish any links if the user move the page within the site hierachy and hence changes the url. (I am nervous to use GetHashCode for the page becuase, as you say, the algorythm for this may change as the .net framework changes.) Does that sound like an appropriate approach, and perhpas the one you are suggesting? Thanks, JJ > Hi JJ, > [quoted text clipped - 301 lines] >>>>>>>>> Please tell me if I'm not making myself clear. >>>>>>>>> JJ Thanks for your followup JJ, For the cookie, I'm sure it is necessary for personalization. Without cookie, how does the site know whether this is you or any other guys who visit this site again(especially for anonymous users). And for ControlID and GetHashCode, as mentioned in previous messages, they can help identify a control on a page at the moment, but it is not qualified to be a means to generated uniqueID that will remain the same at different times a user visit the web application(or page). That means, the result you calculated via it maybe XXX today, and will be YYY tommorrow. I think for such personalization framework(like sharepoint or other portal site), the following implemenation should be reasonable: ** use authentication cookie(or a custom cookie) to identify which user come ** depend on which page the user is visiting, you can use the "user info" + "pageinfo" to query the database for certain personlization data ** after retrieved the data, you can use the data to regenerated the UI of the page Do you think so? I don't think you need an Algorithm that will be able to calculate a constant value at different time. Sincerely, Steven Cheng Microsoft MSDN Online Support Lead This posting is provided "AS IS" with no warranties, and confers no rights. -------------------- >From: "JJ" <abc@xyz.com> >Subject: Re: Web Parts Instances >Date: Mon, 8 Oct 2007 09:59:49 +0100 >Hi Steven, > [quoted text clipped - 243 lines] >>>>>>>> >>>>>>>> Get notification to my posts through email? Please refer to http://msdn.microsoft.com/subscriptions/managednewsgroups/default.aspx#notif >>>>>>>> ications. >>>>>>>> [quoted text clipped - 79 lines] >>>>>>>>>> Please tell me if I'm not making myself clear. >>>>>>>>>> JJ why not use a GUID and store it in the DB. > Hi Steven, > [quoted text clipped - 344 lines] >>>>>>>>>> Please tell me if I'm not making myself clear. >>>>>>>>>> JJ Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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