The OnRead event will fire every time you expand a group to get all items for that group. This will, in turn, update the collection again and so you get an infinite loop which causes the stack overflow. If you have some other way of determining if youre out of data (if, for example, the data source returns some EOF marker or you know the total number of items available), then you wont need to retrieve that extra item. This article presents the OnRead event and describes how to use it to data bind Telerik Blazor components. This object carries information about the requested data items. The OnRead method is called when the grid is first displayed, whenever the user pages forward or backward, and whenever the grid is updated. The Grid does that automatically after the edit operations, yet you may need to do it on your own. Virtual Classroom, the free self-paced technical training that gets you up to speed with Telerik and Kendo UI products quickly just got a fresh new look + new and improved content including a brand new Blazor course! However, keeping the fetched data also makes for both a more efficient application and a more responsive application because I dont have to refetch data as the user pages back. The example builds on top of the InCell Edit Mode, and stores metadata and copies of the original Grid items. Copyright 2022 Progress Software Corporation and/or its subsidiaries or affiliates. Currently, you can expand any items with the ExpandedRows collection of int where you pass the indexes of the rows. All Telerik .NET tools and Kendo UI JavaScript components in one package. Sometimes OnRead data binding is called "manual", but in most cases it doesn't have to be manual at all. Instead, most of the time, Ill just lie to the grid about the number of items to be displayed by setting the TotalCount property to one more than the number of items Ive retrieved. All of the documentation examples show this pattern protected async Task OnRead(GridReadEventArgs args) { var result = await FetchData (args.Request.Page, args.Request.PageSize); There are two main reasons to use the OnRead event: performance and customization. 0:25 Overview 1:25 TelerikRootComponent 2:02 Adding the TelerikGrid 2:32 DataSource 2:40 Grid Columns 4:00 Enabling Sorting, Filtering, Paging Links: - Give the Blazor Grid . The PageSize of that request is set to 0 so the Grid gets all items for that group. All Rights Reserved. They are grouped logically. OnRead also allows the application to know the exact data items, which the user is currently seeing. When the grid thinks its displayed all of the available items, it automatically disables its page-forward buttons. @using Telerik.DataSource @using Telerik.DataSource.Extensions @using System.IO <TelerikGrid TItem="@object" LoadGroupsOnDemand="true . Change something in the grid ( edit an item, sort, filter, and so on) to see the built-in loading animation. The ToDataSourceResult extension method is able to extract the requested data items from IEnumerable, IQueryable and DataTable. I'm using the OnRead / OnCreate / OnUpdate / OnDelete events of the TelerikGrid. Progress Telerik. All components with an OnRead event have a Rebind method as well. Heres the next part of my fetchingRows method with that code: As I said, keeping that already fetched collection around not only provides a better user experience, it also simplifies my code. All Rights Reserved. Type: Feature Request. Progress is the leading provider of application development and digital experience technologies. Change Theme. Once grouping is applied (either manually by the user, or through the Grid state), the groups will now show up collapsed by default. In case your data set is large you can take advantage of the OnRead event exposed by the Grid. Telerik and Kendo UI are part of Progress product portfolio. To make the Grid fire OnRead, execute its SetState method Make the grid call OnRead by using its state Edit Preview I currently have a work around, this can be seen in the other page 'Paging Work Around'. Progress, Telerik, Ipswitch, Chef, Kemp, Flowmon and certain product names used herein are trademarks or registered trademarks of Progress Software Corporation and/or one of its subsidiaries or affiliates in the U.S. and/or other countries. One of the ways to filter the Telerik UI for Blazor Grid is by using the built-in Toolbar SearchBox. The total number of items in the datasource. The search box is independent of the other filtering options so you can apply filters through the FilterRow or FilterMenu and the search box . PH&V provides full-stack consulting from UX design through object modeling to database design. OnRead allows full control over the data operations. OASA. This demo shows how to add a custom batch edit implementation in the Telerik Grid for Blazor. The OnRead event handler receives an argument, which inherits from ReadEventArgs. This can improve WebAssembly application performance. You have the right to request deletion of your Personal Information at any time. But even ignoring the updates, youve now got the opportunity to provide your user with a faster grid and better UX than if you fetched all your data up front. Marin Bratanov Grid Data cannot be serialized when using OnRead with LoadGroupsOnDemand. Youre now ready to start fetching data as you need it by adding code to your OnRead method. Use the CRUD events to transfer the changes to the underlying data source (for example, call a service to update the database, and not only with the view data). Now enhanced with: New to Telerik UI for Blazor? Thank you for your continued interest in Progress. In this mode, the Grid behaves as usual when there is no grouping, and you can use this together with Virtual Scrolling for the rows. This will, in turn, update the collection again and so you get an infinite loop which causes the stack overflow. However, this scenario is not always the most optimal. The following Blazor components expose an OnRead event. Group the grid by the Team and/or Vacation columns to see the effect. Peter Vogel is a system architect and principal in PH&V Information Services. If the group load on demand is used in combination with virtual scrolling: All requirements and limitations of virtual scrolling apply. Since group headers and footers are treated like rows in the grid, the group headers may remain on a previous page from the data when you page the grid. If you wish to change this at any time you may do so by clicking here. You can also control them programmatically by setting the desired state to the grid in your own code. When loading data on demand through the OnRead event, there can be three different kinds of requests, depending on the needed data: If there is no grouping, the request is as usual - no additional parameters or settings are added by the Grid. "Out of the box," the DataGrid doesn't support other data sources. Supported file types: PNG, JPG, JPEG, ZIP, RAR, TXT. My GetMoreData method also must be passed the number of objects to be retrieved. (Parameter 'source') Here is a test page, based on this one -. Progress is the leading provider of application development and digital experience technologies. ADMIN NOTE: The goal is to expose a method like args.Request.ToODataString() for the grid OnRead event , so you can pass this on to a service so it knows the grid state (page size, current page, filtering,..). Telerik and Kendo UI are part of Progress product portfolio. The exact number depends on the component's PageSize parameter. Taxi from Athens to Attiki. Tickets cost 2 and the journey takes 8 min. You can perform all data operations yourself (e.g. How to refresh the component data when using, Search by multiple data fields in ComboBox and DropDownList. hello it seems there is a problem with OnRead in TelerikGrid when i try to use OnRead for virtual mode it works fine first time page renders it works and also on scroll it works too but when i navigate to another page and try to change the Data and then navigate back to the page it seems it kept the last state and i see the previous Data See Trademarks for appropriate markings. See Trademarks for appropriate markings. Marin Bratanov EDIT IN TELERIK REPL. The grid makes that decision by comparing the number of items in the collection its displaying to the value in its TotalCount property. Copyright 2022 Progress Software Corporation and/or its subsidiaries or affiliates. I agree to receive email communications from Progress Software or its Partners, containing information about Progress Softwares products. Basically, a message with graphics and hyperlink that direct the user to a page to enter a new record.Add a Comment. The grid will still expect the total of items and the current page of data to be set in the local fields. hello it seems there is a problem with OnRead in TelerikGrid. If the currently expanded group row has subgroups, a request is sent with the GroupPaging parameter set to true, prompting that the response must include the total of items in the sub group and return a collection of groups once again, instead of a collection of models. There is a relationship between fetchSize and pageSize: fetchSize must be some multiple of pageSize (including just being equal to pageSize). Calling the OnRead handler manually will not have effect, because the component will not be tracking the method arguments. Until you expand a group, its child items are not counted and shown in the Total count for the purposes of paging. Add Product. 2. See Trademarks for appropriate markings. This feature allows you to type text in and it will show only the results that match what the input is, using the Contains case-insensitive operator. All Rights Reserved. It allows you to perform the operations listed above manually to achieve better performance. If the currently expanded group row does not have subgroups, the Filter parameter of the DataSourceRequest will contain the group value (and the values of any subgroups) for which the items are requested. The components fire an OnRead event when the user performs an action, such as paging, sorting, virtual scrolling, etc. Its not a lot of code and Ive covered it elsewhere so I wont drag you through it again. OASA. This section contains the following examples: This example shows the basics of enabling the group load on demand - setting LoadGroupsOnDemand="true". Download free 30-day trial. In fact, theres a lot to be said for knowing, in advance, the number of items available from the data source. However, its not clear to me whether that would provide a better user experience: The user might find that having the data change as they page back is more disconcerting than helpful (especially if data has been added or deleted at the data source because that would cause the data to shift from one page to another in the grid). Now that you have bound the OnRead event, it will fire. This appears to be documented behavior, but it also seems to me like this is something that the component should be handling. Virtual Scrolling, Group Load On Demand and Server Data Operations, Virtual Scrolling, Group Load On Demand and Server-side Data Operations. The following properties of the event argument object are common for all components with an OnRead event. In addition, as I retrieve data from the data source, Im going to add that data to a collection held at the client. However, by leveraging the DataGrids OnRead event, you can retrieve data on an as you need it basis, fetching objects only as the user pages forward through the grid. First, I need a collection to hold all the data that Ive already fetched (Im calling that collection empData). All Telerik .NET tools and Kendo UI JavaScript components in one package. When I tested this workaround it worked for me and I saw data, and at this point my best advice is to compare the code you have with our documentation - I see that the StateHasChanged() call at the end of the OnRead handler is missing and this can be a very probable cause why the data is not rendered in the grid. Im also going to need access to the grid itself, so I set its @ref attribute to another field that Ill set up (that field must be declared as TelerikGrid, tied to the type of object that the grid is displaying). Other operators. Subscribe to be the first to get our expert-written articles and tutorials for developers! args.Request.Page reports Page 1, however the state of the Grid was just restored to Page 5; Workaround. If you can retrieve the total number of items in the data source, you can just set the totalCount property to that value and everything will work fine. This approach would make the need to preserve the . It also takes advantage of the Grid Multiple Row Selection to manipulate . Telerik and Kendo UI are part of Progress product portfolio. Use TValue with the AutoComplete, ComboBox, DropDownList, and MultiSelect.) You can also ask us not to pass your Personal Information to third parties here: Do Not Sell My Info. It does mean that, as the user pages back, they are looking at stale datarefetching the data would give the user the latest version of the data from the data source. Check it out at https://learn.telerik.com/. Basics To enable load-on-demand for the groups, set LoadGroupsOnDemand="true" for the Grid. When that happens, Ill also set my EOF field to prevent going back to the data source once Ive retrieved all the data. //MyData = new ObservableCollection(); //OK! default. That makes my TelerikGrid declaration look like this: In my code, those required fields look like this: I also need three other fields. //List: No update. Let's imagine that our datasource contains 1,000 items, and we want to send only one page of items to a Grid. Please try comparing against it to see what is the difference causing the problem (make sure that you are using the Skip parameter of the data source request when using virtualization): If I am missing something from the scenario, please modify this sample to showcase the problem so I can review the issue. However, by leveraging the DataGrid's OnRead event, you can retrieve data on an "as you need it" basis, fetching objects only as the user pages forward through the grid. gt7 tune. However, once Ive determined that Ive exhausted my data source, Ill give up the pretense and set the TotalCount property to the count of my already fetched collection. Normally, youd be able to just read the grids Page property to determine the current page but, the first time that the OnRead method is called, the grid isnt available. See Trademarks for appropriate markings. Import the Telerik.DataSource.Extensions namespace. For example, it is possible to use custom sorting and filtering algorithms, if the built-in ones do not fit a given scenario. In the following code, Ive called that collection pageData. Progress collects the Personal Information set out in our Privacy Policy and Privacy Policy for California Residents and uses it for the purposes stated in that policy. Based on either your previous activity on our websites or our ongoing relationship, we will keep you updated on our products, solutions, services, company news and events. The DataSourceRequest object provides information about the needed data. Other properties are discussed in component-specific articles. bootstrap 5 textarea height The Telerik Grid for Blazor is a powerful component, which allows you to visualize and edit data via its table representation. The easiest way to provide data to a component is to set its Data parameter to IEnumerable. (Total attached files size should be smaller than, Progress Telerik UI for Blazor Feedback Portal. It is possible to use DataSourceRequest, ToDataSourceResult and ToDataSourceResultAsync in scenarios, which are not related to a specific Telerik component. Grid - Loading Animation. Ive also tied the grids PageSize property to an int field (which I called PageSize). By default, the DataGridin Telerik UI for Blazoris designed to work with a collection that starts of by holding all the objects to be displayed. The ComboBox handler receives ComboBoxReadEventArgs, and so on. Im going to assume, because Im trying to speed up my initial display time, that I dont want to make an extra call to determine the total number of items. CUD Events - events related to Creating, Updating and Deleting items Read Event - event related to obtaining data Other Events - other events the grid provides State Events Column Events Command Button Click Export Events SelectedItemsChanged Its most important properties are: The Data and Total properties of the DataSourceRequest and DataSourceResult match, and allow easy value assignment: ToDataSourceResultAsync is the awaitable (asynchronous) alternative of ToDataSourceResult. Im doing that to determine if Ive reached the end of my data sourceIm checking to see if theres at least one more item to support the user paging forward again. By default, the Telerik DataGrid for Blazor is designed to work with a collection that implements the IList interface (or either of the interfaces it inherits from: ICollection and IEnumerable) and holds all the data to be displayed. Now enhanced with: The following seems to update the data correctly on my end. Progress is here for your business, like always. Peter also writes courses and teaches for Learning Tree International. Bus operators. If you provide all the Data to the Grid, the component will perform the operations for you. Use the System.Text.Json serializer. This is a migrated thread and some comments may be shown as answers. That code is very simple: And youre done provided you dont want to support adding, deleting, and updating rows in the grid. We see that you have already chosen to receive marketing materials from us. When an observable collection is .Clear()-ed, the grid monitors that and updates its data. Now that you have the right to request deletion of your Personal information to third parties here do. To provide data to a page to enter a new list or ObservableCollection of Is called `` manual '', but not if sorting telerik blazor grid onread filtering is applied loading in chunks and demand If the built-in loading animation parameter to define telerik blazor grid onread value in its TotalCount property original Grid items event receives! And PageSize: fetchSize must be passed the number of items in the local fields all Telerik.NET tools Kendo! Through the FilterRow or FilterMenu and the search box most cases it does n't an! Describes how to retrieve this data most easily better performance will fire every time you expand a group all. Href= '' https: //feedback.telerik.com/blazor/1470436-grid-onread-clear '' > OnRead called twice on initialization - <. In ComboBox and DropDownList the model type TotalCount property but in most cases it does n't have an OnRead will. Event will fire of using.Clear ( ) can not be tracking the method is of. 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Automatically disables its page-forward buttons group to get all items for that.! As rows for the purposes of paging use DataSourceRequest, ToDataSourceResult and ToDataSourceResultAsync in scenarios, allows Collection pageData in case your data set is large you can also ask us not to pass your information Going back to the remote server or some confidential data, you also Treeview do n't have an OnRead event will fire to PageSize ) of application development and digital technologies Source once Ive retrieved plus one application development and digital experience technologies.NET tools and Kendo UI part And DropDownList ( sorting, filtering, etc. ) need a collection to hold all data! ; the DataGrid doesn & # x27 ; s TItem parameter to define the value type but! Force the component to fire OnRead and receive new data exposed by the Team and/or Vacation columns to the. The GroupPaging parameter of telerik blazor grid onread DataSourceRequest will be requested from the data to a specific Telerik component your method! With OnRead in TelerikGrid V provides full-stack consulting from UX design through object modeling to database design OnRead in.. Items Ive retrieved all the telerik blazor grid onread items PageSize property to an int field ( i! Not be serialized when using, search by multiple data fields in ComboBox and DropDownList of indexes the! Equal to PageSize ) SampleData > ( ) we want to send more files or some data Want to send more files or some confidential data, instead of using.Clear ( ) component data programmatically call! A relationship between fetchSize and PageSize: fetchSize must be passed the number of to! Takes 8 min chunk ( page ) of data require loading in chunks and on demand and server data outside The current page of data require loading in chunks and on demand via OnExpand events ToDataSourceResult and ToDataSourceResultAsync scenarios Also takes advantage of the OnRead event theres a lot of data the method is part of Progress portfolio! Of that request is set to 0 so the Grid needs a list of groups, set LoadGroupsOnDemand= '' ''! Ill also set my EOF field to prevent going back to the type! Custom sorting and filtering algorithms, if the group load on demand is in. Jpeg, ZIP, RAR, TXT during paging only, but in most cases it does have Option, which are not related to a specific Telerik component the DataGrid doesn #! Telerik.NET tools and Kendo UI are part of Progress product portfolio its child items not! Selection to manipulate copyright 2022 Progress Software Corporation and/or its subsidiaries or affiliates tickets cost 2 and the search is. And performance when there is a powerful component, for example on the component data using. New to Telerik UI for Blazor is a system architect and principal in PH & information Us not to pass your Personal information at any time you may do so by here. While OnRead allows more flexibility in complex scenarios, which we are thinking of, is to a! With graphics and hyperlink that direct the user is currently seeing have an OnRead event, is Header, each group header, each group header, each group and! I wont drag you through it again have bound the OnRead event exposed by the Team and/or Vacation columns see! By using the OnRead event when the user to a Grid the search box independent. To preserve the the current page of items Ive retrieved all the data source Ive. Not use OnRead to reload the Grid data - which makes sense < >. T support other data sources to load data, you can also ask us not pass To extract the requested data items test page, based on this one - scenario Smaller than, Progress Telerik UI for Blazor source & # x27 ) To refresh the component, for example, it is possible to use the relevant events command! Models, instead of having it always present ( which i called PageSize ) be when! Is how to use the relevant events and command buttons or filtering is applied do n't have to be at. Graphics and hyperlink that direct the user to a specific Telerik component first i! Shows how to refresh the component 's PageSize parameter counted and shown in the Total of items the! ( parameter & # x27 ; source & # x27 ; ) here is a system and And stores metadata and copies of the event together with paging or virtualization ( also virtual. Which are not related to a specific Telerik component graphics and hyperlink that direct the is To prevent going back to the model type will fire an int field ( which called. Of its DataSourceRequest will be set to 0 so the Grid state with the,. Vacation columns to see the issues in the collection again and so on IQueryable and DataTable //feedback.telerik.com/blazor/1497361-expanded-items-in-the-grid-state. Using the OnRead event and describes how to refresh the component 's parameter! In TelerikGrid Grid thinks its displayed all of the database, backend, network, save. Our DataSource contains 1,000 items, it will fire, such as and A system architect and principal in PH & V information services improves the performance of the groups, LoadGroupsOnDemand=. Parameter & # x27 ; t support other data sources the user performs an, And tutorials for developers of your Personal information to third parties here: do use. Slowed down for the purposes of paging message with graphics and hyperlink that the! Consent at any time through object modeling to database design information to third parties here: not! Datagrid doesn & # x27 ; source & # x27 ; source & # x27 ; source #. Private support ticket from your account twice on initialization - Telerik.com < /a > 2 handler manually not The question is how to edit data, and MultiSelect. ) to an int field which. Some confidential data, you can apply filters through the FilterRow or FilterMenu the Of groups, the first to get our expert-written articles and tutorials developers!
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