GridCommandColumnHeaderTemplateContext.NewEnabled Property

Returns whether the Add operation is available for an asynchronous data source.

Namespace: DevExpress.Blazor

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

NuGet Package: DevExpress.Blazor

Declaration

public bool NewEnabled { get; }

Property Value

Type	Description
Boolean	true if the add operation is available; otherwise, false.

Remarks

A command column contains the predefined CRUD-related buttons (New, Edit, and Delete). You can define the column’s HeaderTemplate to implement a custom New element in the column header.

The Add operation can be temporarily unavailable if you bind a Grid to an asynchronous data source (such as a Server Mode data source or GridDevExtremeDataSource). The NewEnabled context parameter returns false when the Add operation cannot be performed. Once this operation becomes available, this parameter returns true.

In the template, use the NewEnabled parameter to specify the enabled or disabled state for a custom command element. In the same way, you can use the EditEnabled and DeleteEnabled parameters in the command column’s CellDisplayTemplate.

Razor

@using Microsoft.EntityFrameworkCore
@using DevExpress.Data.Linq
@inject IDbContextFactory<NorthwindContext> NorthwindContextFactory
@implements IDisposable

<DxGrid Data="InstantFeedbackSource"
        EditModelSaving="OnEditModelSaving"
        DataItemDeleting="OnDataItemDeleting"
        KeyFieldName="OrderId"
        EditMode="GridEditMode.EditRow"> 
    <Columns>
        <DxGridCommandColumn Width="150px">
            <HeaderTemplate>
                <DxButton Click="() => context.Grid.StartEditNewRowAsync()"
                          Enabled="context.NewEnabled" Text="Add" />
            </HeaderTemplate>
            <CellDisplayTemplate>
                @{
                    <DxButton Click="() => context.Grid.StartEditDataItemAsync(context.DataItem)"
                              Text="Edit" Enabled="context.EditEnabled"/>
                    <DxButton Click="() => context.Grid.ShowDataItemDeleteConfirmation(context.DataItem)"
                              Text="Delete" Enabled="context.DeleteEnabled"/>
                }
            </CellDisplayTemplate>
        </DxGridCommandColumn>
        <DxGridDataColumn FieldName="ShipName" />
        <DxGridDataColumn FieldName="ShipCountry" />
        <DxGridDataColumn FieldName="Freight"  />
        <DxGridDataColumn FieldName="OrderDate" />
    </Columns>
</DxGrid>

@code {
    EntityInstantFeedbackSource InstantFeedbackSource { get; set; }
    NorthwindContext Northwind { get; set; }

    protected override void OnInitialized() {
        Northwind = NorthwindContextFactory.CreateDbContext();
        InstantFeedbackSource = new EntityInstantFeedbackSource(e => {
            e.KeyExpression = "OrderId";
            e.QueryableSource = Northwind.Orders;
        });
    }

    async Task OnEditModelSaving(GridEditModelSavingEventArgs e) {
        var editModel = (Order)e.EditModel;
        var dataItem = e.IsNew ? new Order() : Northwind.Orders.Find(editModel.OrderId);
        if (dataItem != null) {
            dataItem.ShipName = editModel.ShipName;
            dataItem.ShipCountry = editModel.ShipCountry;
            dataItem.Freight = editModel.Freight;
            dataItem.OrderDate = editModel.OrderDate;
            if (e.IsNew)
                await Northwind.AddAsync(dataItem);
            await Northwind.SaveChangesAsync();
        }
    }

    async Task OnDataItemDeleting(GridDataItemDeletingEventArgs e) {
        var orderId = (int)e.Grid.GetDataItemValue(e.DataItem, "OrderId");
        var dataItem = Northwind.Orders.Find(orderId);
        if (dataItem != null) {
            Northwind.Remove(dataItem);
            await Northwind.SaveChangesAsync();
        }
    }

    public void Dispose() {
        InstantFeedbackSource?.Dispose();
        Northwind?.Dispose();
    }
}

Employee

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;

namespace Grid.Northwind {
    public partial class Employee {
        public int EmployeeId { get; set; }
        [Required]
        public string LastName { get; set; }
        [Required]
        public string FirstName { get; set; }
        [Required]
        public string Title { get; set; }
        public string TitleOfCourtesy { get; set; }
        public Nullable<System.DateTime> BirthDate { get; set; }
        [Required]
        [Range(typeof(DateTime), "1/1/2000", "1/1/2020",
        ErrorMessage = "HireDate must be between {1:d} and {2:d}")]
        public Nullable<System.DateTime> HireDate { get; set; }
        public string Address { get; set; }
        public string City { get; set; }
        public string Region { get; set; }
        public string PostalCode { get; set; }
        public string Country { get; set; }
        public string HomePhone { get; set; }
        public string Extension { get; set; }
        public byte[] Photo { get; set; }
        public string Notes { get; set; }
        public Nullable<int> ReportsTo { get; set; }
        public string PhotoPath { get; set; }
        public virtual ICollection<Order> Orders { get; set; }
        public string Text => $"{FirstName} {LastName} ({Title})";
        public string ImageFileName => $"Employees/{EmployeeId}.jpg";
    }
}

NorthwindContext

using Microsoft.EntityFrameworkCore;
#nullable disable

namespace Grid.Northwind {
    public partial class NorthwindContext : DbContext {

        public NorthwindContext(DbContextOptions<NorthwindContext> options)
            : base(options) {
        }
        // ...
        public virtual DbSet<Employee> Employees { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) {
            if(!optionsBuilder.IsConfigured) {
                optionsBuilder.UseSqlServer("Server=.\\sqlexpress;Database=Northwind;Integrated Security=true");
            }
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder) {
            modelBuilder.HasAnnotation("Relational:Collation", "SQL_Latin1_General_CP1_CI_AS");
            // ...
            modelBuilder.Entity<Employee>(entity => {
                entity.HasIndex(e => e.EmployeeId, "EmployeeId");
                entity.HasIndex(e => e.LastName, "LastName");
                entity.HasIndex(e => e.FirstName, "FirstName");
                entity.HasIndex(e => e.Title, "Title");
                entity.HasIndex(e => e.BirthDate, "BirthDate");
                entity.HasIndex(e => e.HireDate, "HireDate");
                entity.HasIndex(e => e.Notes, "Notes");
            });
            OnModelCreatingPartial(modelBuilder);
        }

        partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
    }
}

Program.cs

using Microsoft.EntityFrameworkCore;
// ...
builder.Services.AddDbContextFactory<NorthwindContext>((sp, options) => {
    var env = sp.GetRequiredService<IWebHostEnvironment>();
    var dbPath = Path.Combine(env.ContentRootPath, "Northwind-5e44b51f.mdf");
    options.UseSqlServer("Server=(localdb)\\MSSQLLocalDB;Integrated Security=true;AttachDbFileName=" + dbPath);
});

Tip

For additional information on how to enable data editing, refer to the following topic: Editing and Validation in Blazor Grid.