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Binding a large list takes too long

Hi Team,

I have two dropdowns. On select of first one, I am populating list in the second dropdown by binding values. The problem is if the list is too large, the UI hangs for good 10 seconds and then loads the list. Is there any solution to this? 

Do we have virtual scrolling supported in this component? Another way I would like is to type in few characters (say 3 or 4 ) and make a call to api to bring related items only. That way only searched items will be binded and not all.

Thanks in advance!

1 Reply

SP Sureshkumar P Syncfusion Team November 4, 2019 10:04 AM UTC

Hi Samir, 
Greetings from Syncfusion support. 
We have checked your query. While working with huge amount of data, we suggest you use Virtual Scrolling technique which loads items on demand. We can achieve this by loading items manually on scrolling. Here we have initially loaded some items using take property in query. And when you scroll the popup dynamically, we have updated the list items by demand. We can use the open event in the multiselect control and bind the scroll event for the popup list event. Kindly refer to the following code snippet 
public onOpen(args){ 
    let start: number = 7; 
    let end: number = 12; 
    let listElement: HTMLElement = (this.multiselectObj as any).list; 
    listElement.addEventListener('scroll', () => { 
        if ((listElement.scrollTop + listElement.offsetHeight >= listElement.scrollHeight)) { 
            let filterQuery = this.multiselectObj.query.clone(); 
            this.data.executeQuery(filterQuery.range(start, end)).then((event: any) => { 
                start = end; 
                end += 5; 
                this.multiselectObj.addItem(event.result as { [key: string]: Object }[]); 
            }).catch((e: Object) => { 
We created a sample based on your requirement. please refer the sample here: https://stackblitz.com/edit/angular-lm3yxp-cxdfbh?file=app.component.ts  
Also, to limit the number of requests to send to server, we suggest to refer the below documentation. 
Sureshkumar P 

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