Control events

It's possible to define interaction behaviors between controls through events.

All events are based on the value of the source control to modify the properties of target controls.

 

There are three types of events:

 

In general, target controls refer to those with a Name or GroupName specified in the TargetNames field of the method.

In fact, events allow creating dependencies between controls and control groups while minimizing the amount of code.

 

ControlBase provides methods to quickly create typed events. These methods add the event to the Events list of the control. The list will be executed during the form rendering phase. Here, for example, is the implementation of AddEventSetIsVisible:

 

public void AddEventSetIsVisible(EventCondition condition, List<string> referenceValues, List<string> targetNames, bool isKeepValueOnHidden = true)
        {
            this.Events.Add(new Event()
            {
                Type = EventType.SetIsVisible,
                Condition = condition,
                ReferenceValues = referenceValues,
                TargetNames = targetNames,
                IsKeepValueOnHidden = isKeepValueOnHidden
            });
        }

With this event, we can modify the data of a target control based on the current value of the source control (and other preceding controls). For example, we can establish a relationship between two DropDownList controls so that selecting a value in the first one (e.g., AreaName) corresponds to loading cascading data in the second one (e.g., CategoryName).

The event can be added using the AddEventSetDataSourceParameter method, which allows specifying source controls (ReferenceNames) and target controls (TargetNames). This way, we can pass multiple source values to the target for more advanced solutions (such as three cascading DropDownList controls).

 

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Extensions.DependencyInjection;
using DataWeb.Data;
using DataWeb.Data.Controls;
using DataWeb.WebApp.Infrastructure;
using Microsoft.Extensions.Localization;

namespace MyApp.DataWeb.Data.Controls
{
    public class Product_AreaName :  DropDownList
    {
        private readonly AreaRepository areaRepository;
        private readonly IStringLocalizer localizer;

        public Product_AreaName(Form form, IServiceProvider serviceProvider) : base(form, serviceProvider)
        {
            areaRepository = serviceProvider.GetService<AreaRepository>();
            localizer = serviceProvider.GetService<IStringLocalizer>();
        }

        public override async Task InitAsync()
        {
            await base.InitAsync();

            AddEventSetDataSourceParameter(new List<string> { "AreaName" }, new List<string> { "CategoryName" });
        }
    }
}

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using DataWeb.Data;
using DataWeb.Data.Controls;

namespace MyApp.DataWeb.Data.Controls
{
    public class News_IsTermTime :  DropDownList
    {
        public News_IsTermTime(Form form, IServiceProvider serviceProvider) : base(form, serviceProvider)
        {
        }

        public override async Task InitAsync()
        {
            await base.InitAsync();

            AddEventSetIsVisible(EventCondition.IsEqual, new List<string> { "True" }, new List<string> { "TermTime" });
        }
    }
}