DxComboBox<TData, TValue>.CustomData Property

Specifies an asynchronous function that loads ComboBox data based on the specified load options.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.v23.2.dll

NuGet Package: DevExpress.Blazor

Declaration

[Parameter]
public Func<DataSourceLoadOptionsBase, CancellationToken, Task<LoadResult>> CustomData { get; set; }

Property Value

Type	Description
Func<DevExtreme.AspNet.Data.DataSourceLoadOptionsBase, CancellationToken, Task<DevExtreme.AspNet.Data.ResponseModel.LoadResult>>	A delegate that implements data load logic.

Remarks

To bind the ComboBox to data that is stored on a remote service and is loaded through a Web API, assign the data type to the component’s T parameter and use the CustomData property to implement data load logic. This property specifies an asynchronous function that accepts two parameters:

• The DataSourceLoadOptionsBase object, which reflects the current ComboBox state.
• The CancellationToken object, which propagates a cancellation notification.

In this function, you can use the ConvertToGetRequestUri and ConvertToHttpContent extension methods to generate HTTP requests with parameters based on data load options. The function should return a Task<LoadResult> object.

Controller

On a remote service, implement an API controller and create action methods that use the DevExtreme.AspNet.Data library’s DataSourceLoader class to create a LoadResult object based on load options. If you pass a DataSourceLoadOptions class instance as an argument in controller actions, add a reference to the DevExtreme.AspNet.Mvc namespace from the DevExtreme.AspNet.Core NuGet package.

Example

Razor

@using CustomData.Data
@using DevExtreme.AspNet.Data
@using DevExtreme.AspNet.Data.ResponseModel
@using System.Threading
@using System.Threading.Tasks
@using System.Net.Http
@using System.Text.Json

<DxComboBox TData=WebApiLookup 
            TValue=System.String
            CustomData="@LoadCustomData"
            @bind-Value="@Value"
            TextFieldName="Text" >
</DxComboBox>

@code {
    string Value { get; set; }
    [Inject] protected HttpClient Client { get; set; }

    protected Task<LoadResult> LoadCustomData(DataSourceLoadOptionsBase options, CancellationToken cancellationToken) {
        return CustomDataHelper.LoadCustomData(Client, options, cancellationToken);
    }
}

Program.cs

builder.Services.AddHttpClient<HttpClient>(ConfigureHttpClient);
builder.Services.AddScoped<HttpClient>(serviceProvider => serviceProvider.GetService<IHttpClientFactory>().CreateClient());
static void ConfigureHttpClient(HttpClient httpClient) {
    httpClient.DefaultRequestHeaders.Add("Accept", "application/json");
};

Web API Controller

using DevExtreme.AspNet.Data;
using DevExtreme.AspNet.Mvc;
// ...
namespace CustomData.Data {
    [Route("api /[controller] /[action]")]
    public class DataGridWebApiController : Controller {
        NorthwindContext _nwind;

        [HttpGet]
        public object CustomersLookup(DataSourceLoadOptions loadOptions) {
            var lookup = from i in _nwind.Customers
                         let text = i.CompanyName + " (" + i.Country + ")"
                         orderby i.CompanyName
                         select new {
                             Value = i.CustomerId,
                             Text = text
                         };

            return DataSourceLoader.Load(lookup, loadOptions);
        }
        // ...
    }
}

View Example: Data Editors for Blazor - Custom data binding