GridCustomDataSourceUniqueValuesOptions.FieldName Property

Specifies a data source field containing values that the GetUniqueValuesAsync method returns.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.Grid.v26.1.dll

NuGet Package: DevExpress.Blazor

Declaration

public string FieldName { get; }

Property Value

Type	Description
String	The data field’s name.

Remarks

If standard data binding modes do not meet specific business requirements, you can implement your own data provider. To do so, create a GridCustomDataSource descendant and assign it to the Grid or TreeList component’s Data property.

The following code snippet implements a custom data provider’s GetUniqueValuesAsync method:

View Example: Custom Data Source Binding using Entity Framework Core

using DevExpress.Blazor;
using DevExpress.Data.Filtering;
using DevExpress.Data.Filtering.Helpers;
using CustomDataSource.Models;
using System.Collections;
using System.Linq.Expressions;
using DevExpress.Data.Linq;
using DevExpress.Data.Linq.Helpers;
using Microsoft.EntityFrameworkCore;

namespace CustomDataSource.Services;

public class OrdersDataSource : GridCustomDataSource, IDisposable {
    protected override Type DataItemType => typeof(Order);
    private readonly NorthwindContext _context;
    private bool _disposed = false;

    public OrdersDataSource(IDbContextFactory<NorthwindContext> contextFactory) {
        _context = contextFactory.CreateDbContext();
    } 
    // ...
    public override Task<object[]> GetUniqueValuesAsync(GridCustomDataSourceUniqueValuesOptions options, CancellationToken cancellationToken) {
        var filteredQuery = ApplyFiltering(options.FilterCriteria, _context.Orders);
        var lambda = GetTypedLambda(options.FieldName);
        return filteredQuery
            .Select(lambda)
            .Distinct()
            .OrderBy(x => x)
            .ToArrayAsync(cancellationToken);
    }
    // ...
    private static IQueryable<Order> ApplyFiltering(CriteriaOperator criteria, IQueryable<Order> queryableSource) {
        return !criteria.ReferenceEqualsNull()
            ? (IQueryable<Order>)queryableSource.AppendWhere(
                new CriteriaToEFExpressionConverter(queryableSource.Provider.GetType()), criteria)
            : queryableSource;
    }
    // ...
    private static Expression<Func<Order, object>> GetTypedLambda(string fieldName) {
        var parameter = Expression.Parameter(typeof(Order));
        var property = Expression.Property(parameter, fieldName);
        var lambda = Expression.Lambda<Func<Order, object>>(Expression.Convert(property, typeof(object)), parameter);
        return lambda;
    }
    // ...
    public void Dispose() {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing) {
        if (!_disposed) {
            if (disposing) {
                _context?.Dispose();
            }
            _disposed = true;
        }
    }
    // ...
}

Related GitHub Examples

The following code snippet (auto-collected from DevExpress Examples) contains a reference to the FieldName property.

Note

The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.

C#

blazor-grid-custom-datasource-with-ef-core/CS/CustomDataSource/Services/OrdersDataSource.cs#L42

var filteredQuery = ApplyFiltering(options.FilterCriteria, _context.Orders);
var lambda = GetTypedLambda(options.FieldName);
return filteredQuery