Large amounts of data require loading in chunks and on demand. OnRead allows full control over the data operations. PH&V provides full-stack consulting from UX design through object modeling to database design. I acknowledge my data will be used in accordance with Progress' Privacy Policy and understand I may withdraw my consent at any time. Virtual Scrolling, Group Load On Demand and Server Data Operations, Virtual Scrolling, Group Load On Demand and Server-side Data Operations. You can also control them programmatically by setting the desired state to the grid in your own code. My GetMoreData method also must be passed the number of objects to be retrieved. Each component name points to component-specific OnRead documentation and examples: Components like the TreeList and the TreeView don't have an OnRead event. 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. Regards, Tickets cost 2 and the journey takes 8 min. Without that collection, Id have to main the totalCount field myself as the maximum number of items Ive retrieved plus one. Copyright 2022 Progress Software Corporation and/or its subsidiaries or affiliates. 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. When that happens, Ill also set my EOF field to prevent going back to the data source once Ive retrieved all the data. There is a relationship between fetchSize and pageSize: fetchSize must be some multiple of pageSize (including just being equal to pageSize). 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. Bus operators. So, for the first page, the number of items to skip is zero, but for any other page, its the page count times the page size: With that number in hand, I can check to see if theres enough data in my already fetched collection to support displaying the page (I also check my EOF field to see if Ive reached the end of the data sourcemore on that later). The chunk (page) of data items to render. 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. I'm using the OnRead / OnCreate / OnUpdate / OnDelete events of the TelerikGrid. Youre now ready to start fetching data as you need it by adding code to your OnRead method. The grid makes that decision by comparing the number of items in the collection its displaying to the value in its TotalCount property. Add Product. Another option, which we are thinking of, is to provide a Collection<Model>. Type: Feature Request. One of the ways to filter the Telerik UI for Blazor Grid is by using the built-in Toolbar SearchBox. Marin Bratanov To refresh the component data programmatically, call this method. Progress Telerik. 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 . It will force the component to fire OnRead and receive new data. We have data coming from an API endpoint that handles paging, filtering, and sorting, so we are using manual data source operations through OnRead. And faster is always better. The workaround is to assign a new List or ObservableCollection instead of using .Clear(). //MyData = new ObservableCollection(); //OK! default. The Grid does that automatically after the edit operations, yet you may need to do it on your own. Now enhanced with: You can use the DataGrid in Telerik UI for Blazorwith any data source you want just by leveraging the OnRead event. (Parameter 'source') Here is a test page, based on this one -. Now that you have bound the OnRead event, it will fire. Retrieving Data "As You Need It" with the Telerik UI for Blazor DataGrid, .NET Basics: ORM (Object Relational Mapping), Whats New in R3 2022 With Telerik UI Web Components, When there is so much data that retrieving it all would result in unacceptably long start-up times, When users typically find what theyre looking for in the first few pages that the grid displays (these first two scenarios overlap). When the grid thinks its displayed all of the available items, it automatically disables its page-forward buttons. 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. Sometimes OnRead data binding is called "manual", but in most cases it doesn't have to be manual at all. I have two reasons for that, the first being that, as youll see, it simplifies my code. Marin Bratanov See Trademarks for appropriate markings. Once grouping is applied (either manually by the user, or through the Grid state), the groups will now show up collapsed by default. Calling the OnRead handler manually will not have effect, because the component will not be tracking the method arguments. If you provide all the Data to the Grid, the component will perform the operations for you. Taxi from Athens to Attiki. Regards, You can also ask us not to pass your Personal Information to third parties here: Do Not Sell My Info. The ToDataSourceResult extension method is able to extract the requested data items from IEnumerable, IQueryable and DataTable. The following Blazor components expose an OnRead event. We see that you have already chosen to receive marketing materials from us. I agree to receive email communications from Progress Software or its Partners, containing information about Progress Softwares products. For example, the Grid handler receives GridReadEventArgs. 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. The example builds on top of the InCell Edit Mode, and stores metadata and copies of the original Grid items. (Some components require a TValue parameter to define the value type, but not the Grid. Zero Records Message (NoDataTemplate) I would like to display a message where rows would be displayed in grid, when there are no records returned from the data source. The method is part of the Telerik DataSource Extensions. This section contains the following examples: This example shows the basics of enabling the group load on demand - setting LoadGroupsOnDemand="true". on the server) and load data on demand by using the OnRead event of the Grid. There are, at least, three scenarios when you want dont want to retrieve all of your data up front: For this case study, Im going to assume the existence of a method that lets me retrieve more data from my data source (Ive called that method GetMoreData). EDIT IN TELERIK REPL. Telerik UI for Blazor Data Grid Watch on Data Binding The are two main ways to provide data to the Grid - via the Data parameter and via the OnRead event. Use the System.Text.Json serializer. All Rights Reserved. All Telerik .NET tools and Kendo UI JavaScript components in one package. 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. Other properties are discussed in component-specific articles. All Telerik .NET tools and Kendo UI JavaScript components in one package. This example shows how you can combine the virtual row scrolling feature with loading group data on demand through a remote service (mocked by a static class in this example so you can run it easily), and how to set the initial state of the grid to have grouping by default. All Rights Reserved. EXAMPLE. Progress Telerik. The DataSourceRequest object provides information about the needed data. I will add this info to the docs . Max total file size - 20MB. That code is very simple: And youre done provided you dont want to support adding, deleting, and updating rows in the grid. Set the Grid's TItem parameter to the model type. OASA. This improves the performance of the database, backend, network, and the browser. Download free 30-day trial. There are two main reasons to use the OnRead event: performance and customization. Data operations are intentionally slowed down for the purpose of the demo. About Sotheby's International Realty Affiliates LLC. System.ArgumentNullException: Value cannot be null. When exporting only the current Grid page (AllPages="false"), the exported file will not contain child data for collapsed groups. It is possible to use DataSourceRequest, ToDataSourceResult and ToDataSourceResultAsync in scenarios, which are not related to a specific Telerik component. When an observable collection is .Clear()-ed, the grid monitors that and updates its data. Grid Data cannot be serialized when using OnRead with LoadGroupsOnDemand. 24. OnRead also allows the application to know the exact data items, which the user is currently seeing. Copyright 2022 Progress Software Corporation and/or its subsidiaries or affiliates. They are grouped logically. 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. Copyright 2022 Progress Software Corporation and/or its subsidiaries or affiliates. Finally, I need to keep track of when Ive pulled all the data from the data source so I also set up a Boolean field called EOF. It expects a DataSourceRequest argument. 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. Other operators. 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. Check it out at https://learn.telerik.com/. The OnRead method is called when the grid is first displayed, whenever the user pages forward or backward, and whenever the grid is updated. First, I need a collection to hold all the data that Ive already fetched (Im calling that collection empData). This allows the component to have all data items and to perform all data operations internally (filtering, paging, sorting, etc.). You have the right to request deletion of your Personal Information at any time. While grouping is active, paging and virtual scrolling operations do not trigger OnRead, because the Grid already has all the group headers and all the items from the currently expanded groups. Founded in 1976 to provide independent brokerages with a powerful marketing and referral program for luxury listings, the Sotheby's International Realty network was designed to connect the finest independent real estate companies to the most prestigious clientele in the world. Peter Vogel is a system architect and principal in PH&V Information Services. Rebind DropDownList and Grid when using OnRead. The DataGrid in Telerik UI for Blazor's lifecycle events makes it easy to both simplify and centralize functionality that it would otherwise require more complex code spread across multiple events to implement.. "/> There is also a runnable code example. The last step in the OnRead method is to update the collection that the grid is bound to (pageData, in my case) with a selection from the already fetched collection. 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. Description By default, the Grid receives the entire data collection and performs operations like paging, sorting, and filtering automatically. It also takes advantage of the Grid Multiple Row Selection to manipulate . Basically, a message with graphics and hyperlink that direct the user to a page to enter a new record.Add a Comment. 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. The following properties of the event argument object are common for all components with an OnRead event. This approach would make the need to preserve the . If the Grid starts with grouping set, it will make one request for the list of all groups, and will keep them in memory for paging. 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. When performing an update two events will fire, such as OnCreate and then OnRead to reload the grid data - which makes sense. The OnRead event handler receives an argument, which inherits from ReadEventArgs. The DataSourceRequest object can be serialized and sent to the remote server. The first step in setting up the grid for as you need it retrieval is to tie the to some field declared as a List, tied to the object type youre displaying (in my case, Ill be displaying Employee objects). Subscribe to be the first to get our expert-written articles and tutorials for developers! This can improve WebAssembly application performance. To do that, I just set the TotalCount field that I bound to the grids TotalCount property to one more than the number of items in my already fetched collection. See Trademarks for appropriate markings. Changing OnRead to async makes no difference. For example, it is possible to use custom sorting and filtering algorithms, if the built-in ones do not fit a given scenario. The question is how to retrieve this data most easily. This article explains the events available in the Telerik Grid for Blazor. Once you take control of the OnRead event, you also have to provide methods for some combination of the OnDelete, OnCreate, and OnUpdate events plus a method to support adding a new, blank row. If you need to send more files or some confidential data, you can also open a private support ticket from your account. See Trademarks for appropriate markings. 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. This is a migrated thread and some comments may be shown as answers. Now that you have bound the OnRead event, it will fire. Train operators. 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). Now enhanced with: The following seems to update the data correctly on my end. @using Telerik.DataSource @using Telerik.DataSource.Extensions @using System.IO <TelerikGrid TItem="@object" LoadGroupsOnDemand="true . For details about server operations, see below. VIEW SOURCE. See Trademarks for appropriate markings. The exact number depends on the component's PageSize parameter. Data provides simplicity, while OnRead allows more flexibility in complex scenarios, and performance when there is a lot of data. Progress is the leading provider of application development and digital experience technologies. 2. The ComboBox handler receives ComboBoxReadEventArgs, and so on. args.Request.Page reports Page 1, however the state of the Grid was just restored to Page 5; Workaround. Alternatively, OASA operates a bus from to every 5 minutes. 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,..). To gain performance benefits, use the event together with paging or virtualization (also called virtual scrolling). All Telerik .NET tools and Kendo UI JavaScript components in one package. All Rights Reserved. //with Virtual Scrolling, make sure to use the Skip parameter for paging, //simulate network delay from a real async call. Grid - Loading Animation. All of the documentation examples show this pattern protected async Task OnRead(GridReadEventArgs args) { var result = await FetchData (args.Request.Page, args.Request.PageSize); This page explains how to enable editing, use the relevant events and command buttons. 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. Currently, you can expand any items with the ExpandedRows collection of int where you pass the indexes of the rows. gt7 tune. 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. Progress is the leading provider of application development and digital experience technologies. In the following code, Ive called that collection pageData. When the user expands a group, all its rows will be requested from the data source. This will, in turn, update the collection again and so you get an infinite loop which causes the stack overflow. Progress, Telerik, 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. The expanded state of the groups is preserved during paging only, but not if sorting or filtering is applied. This Blazor Grid - Persist State demo is part of a unique collection of hundreds of Blazor demos, with which you can see all Telerik Blazor components and their features in action. If you wish to change this at any time you may do so by clicking here. To enable filtering, set the grid's FilterMode property to one of the following values: Telerik.Blazor.GridFilterMode.FilterRow - a row of filter options is rendered below the column headers Telerik.Blazor.GridFilterMode.FilterMenu - the column headers render a button that shows a popup with filtering options To make the Grid fire OnRead, execute its SetState method Make the grid call OnRead by using its state Edit Preview
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