Boost MultiColumn ComboBox Performance with Virtual Scrolling and Paging

TL;DR: This blog discusses improving the performance of the Syncfusion Blazor MultiColumn ComboBox when handling large datasets, which can cause slow loading and scrolling. It highlights two key techniques: virtualization, which loads only visible items to minimize DOM elements and enhance scrolling; and paging, which breaks data into smaller chunks, loading them one at a time to reduce server load and improve navigation. Implementing these strategies is crucial for building responsive and user-friendly web applications.

Handling large datasets efficiently is crucial for delivering smooth user experiences in modern web applications. The Blazor MultiColumn ComboBox is a versatile component that supports multiple columns of data in its dropdown, making it ideal for presenting complex data. However, as the dataset grows, rendering all items at once can degrade performance without proper optimization.

This blog post delves into two powerful techniques: virtualization , which renders only the items currently in view to minimize DOM overhead, and paging , which splits the data into manageable pages loaded on demand to reduce memory and network usage to dramatically boost rendering speed and overall responsiveness when using the MultiColumn ComboBox.

Getting started with MultiColumn ComboBox

If you’re new to the Syncfusion Blazor MultiColumn ComboBox, it’s easy to begin. This component allows you to display multiple columns in the dropdown, providing a user-friendly way to showcase complex datasets. You can visit the official documentation site for more details.

The challenge of large datasets

When dealing with thousands or millions of records, loading and rendering all data at once can lead to:

• Slow initial load times: Rendering many items in the DOM increases the load time and memory usage.

• Laggy scrolling: Without optimization, scrolling through a lengthy list may result in delays or freezes.

• Poor user experience: Users may face unresponsive dropdowns and degraded performance.

Virtualization and paging offer solutions to these challenges by ensuring that only the data relevant to the user’s current view or interaction is rendered.

Implementing virtualization in MultiColumn ComboBox

Virtualization dynamically loads and renders only the visible items in the dropdown list instead of the entire dataset. This approach minimizes the DOM elements, reducing memory usage and improving scrolling performance.

Key benefits

• Faster load times: Initial rendering is limited to a small subset of items.

• Improved scrolling: Smooth scrolling experience even with large datasets.

• Optimized memory usage: Only necessary data is kept in memory.

How to enable virtualization

The MultiColumn ComboBox supports virtualization through the EnableVirtualization property. Here’s how you can implement it:

@using Syncfusion.Blazor
@using Syncfusion.Blazor.MultiColumnComboBox

<PageTitle>MultiColumn ComboBox</PageTitle>
<h2>MultiColumn ComboBox</h2>
<br/>

<SfMultiColumnComboBox
    TItem="Employee"
    TValue="string"
    EnableVirtualization="true"
    TextField="Name"
    Width="600px"
    DataSource="@Employees"
    ValueField="Name"
    Placeholder="Pick an Employee">
</SfMultiColumnComboBox>

@code {
    public class Employee
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Department { get; set; }
        public string Role { get; set; }
        public string Location { get; set; }
        public int Experience { get; set; }
    }

    private string Value { get; set; } = "Alice Johnson";
    private List Employees = new List();

    protected override Task OnInitializedAsync()
    {
        var employees = new List();
        string[] names = { "John Doe", "Jane Smith", "Alice Johnson", "Bob Brown", "Emily Davis" };
        string[] departments = { "HR", "IT", "Finance", "Marketing", "Sales" };
        string[] roles = { "Manager", "Developer", "Analyst", "Consultant", "Executive" };
        string[] locations = { "New York", "San Francisco", "London", "Berlin", "Tokyo" };
        var rand = new Random();

        for (int i = 1; i <= 20000; i++)
        {
            employees.Add(new Employee
            {
                ID = i,
                Name = names[rand.Next(names.Length)],
                Department = departments[rand.Next(departments.Length)],
                Role = roles[rand.Next(roles.Length)],
                Location = locations[rand.Next(locations.Length)],
                Experience = rand.Next(1, 21) // Experience between 1 and 20 years
            });
        }

        Employees = employees;
        return base.OnInitializedAsync();
    }
}

When to use virtualization

• Ideal for datasets where scrolling is the primary navigation mode.

• When a large dataset is loaded on the client-side, rendering performance is a concern.

Implementing paging for MultiColumn ComboBox

Paging segments the dataset into smaller, manageable chunks or pages, loading only one page at a time. This technique is particularly useful when users browse or search through structured data. A pager component at the bottom of the MultiColumn ComboBox popup allows users to navigate between these pages, ensuring only the current page’s data is loaded and displayed.

Key benefits

1. Controlled data loading: Only one data page is fetched at a time, reducing server load.

2. Better user experience: Users can navigate smaller data sets, improving performance.

3. Simpler debugging: Easier to monitor and debug due to smaller data transactions.

How to enable paging

To enable paging in the MultiColumn ComboBox , set the AllowPaging property to true. This activates the pager, which facilitates navigation through different pages of data. Paging can be further customized by using the PageSize and PageCount properties.

Here’s how you can implement it:

@using Syncfusion.Blazor  
@using Syncfusion.Blazor.MultiColumnComboBox  

<PageTitle>MultiColumn ComboBox</PageTitle>  
<h2>MultiColumn ComboBox</h2>  
<br/>  

<SfMultiColumnComboBox  
    TItem="Employee"  
    TValue="string"  
    AllowPaging="true"  
    PageSize="1000"  
    PageCount="20"  
    TextField="Name"  
    Width="600px"  
    DataSource="@Employees"  
    ValueField="Name"  
    Placeholder="Pick an Employee">  
</SfMultiColumnComboBox>  

@code {  
    public class Employee  
    {  
        public int ID { get; set; }  
        public string Name { get; set; }  
        public string Department { get; set; }  
        public string Role { get; set; }  
        public string Location { get; set; }  
        public int Experience { get; set; }  
    }  

    private string Value { get; set; } = "Alice Johnson";  
    private List Employees = new List();  

    protected override Task OnInitializedAsync()  
    {  
        var employees = new List();  
        string[] names = { "John Doe", "Jane Smith", "Alice Johnson", "Bob Brown", "Emily Davis" };  
        string[] departments = { "HR", "IT", "Finance", "Marketing", "Sales" };  
        string[] roles = { "Manager", "Developer", "Analyst", "Consultant", "Executive" };  
        string[] locations = { "New York", "San Francisco", "London", "Berlin", "Tokyo" };  
        var rand = new Random();  

        for (int i = 1; i <= 20000; i++)  
        {  
            employees.Add(new Employee  
            {  
                ID = i,  
                Name = names[rand.Next(names.Length)],  
                Department = departments[rand.Next(departments.Length)],  
                Role = roles[rand.Next(roles.Length)],  
                Location = locations[rand.Next(locations.Length)],  
                Experience = rand.Next(1, 21) // Experience between 1 and 20 years  
            });  
        }  

        Employees = employees;  
        return base.OnInitializedAsync();  
    }  
}

When to use paging

• For server-side datasets that are too large to load at once.

• When the dataset is frequently updated, only relevant data is fetched.

Best practices for performance optimization

• Asynchronous data fetching: Ensure operations like fetching and filtering data are asynchronous to avoid blocking the UI thread.

• Customizable loading indicators: Improve user experience by offering feedback during the data fetch.

• Efficient Filtering: Implement server-side filtering to minimize data transfer and processing.

Conclusion

Thanks for reading! This article provides a clear and straightforward guide for optimizing theBlazor MultiColumn ComboBox for extensive datasets, which is crucial for sustaining high application performance and user satisfaction. Elevate your MultiColumn ComboBox to the next level! Implement these techniques today and experience a world of difference.

If you are an existing Syncfusion user, please download the latest version of Essential Studio® from the License and Downloads page. If you aren’t a customer, try our 30-day free trial to check out these features.

You can also explore all the other features rolled out in the Essential Studio® 2025 Volume 1 release on our Release Notes and What’s New pages.

Try out these features and share your feedback as comments on this blog. You can also reach us through our support forums, support portal, or feedback portal.

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