using c# linq to populate/load a list one time to enhance performance

Question

I'm working on an ASP.NET MVC 4.5 application. I need to populate a list in a dropdown. I t works fine, anyhow, when I click the field there is allways a server request.

I'd like to store the values after the initial load on the client side to speed up the application.

I'm using a ViewModel to populate the list in my Razor View.

Do you know how to achieve an initial load of the this?

Here is my DataSource Controller:

public JsonResult GetBusinessLineList(string id = null, string query = null)
{

    return
        Json(Db.BusinessLine.AsQueryable()
            .Where(x => x.Label.Contains(query))
            .Take(10)
            .Select(x => new { id = x.BusinessLineId, text = x.Label })
            .ToList(), 
            JsonRequestBehavior.AllowGet);
}

The Razor View:

<div class="form-group">
    @Html.LabelFor(model => model.BusinessLineIdList, htmlAttributes: new { @class = "control-label col-md-2" })
    <div class="col-md-10">
        @Html.Select2AjaxFor(model => model.BusinessLineIdList, @Url.Action("GetBusinessLineList", "DataSource"),
               new { @class = "form-control"))

    </div>
</div>

Many thanks and kind regards!

Answer 1

You can try to use output cache:

[OutputCache(Location = OutputCacheLocation.Client, VaryByParam = "id;query", Duration = 3600)]
public JsonResult GetBusinessLineList(string id = null, string query = null)
{
    return Json(Db.BusinessLine.AsQueryable()
        .Where(x => x.Label.Contains(query))
        .Take(10)
        .Select(x => new { id = x.BusinessLineId, text = x.Label })
        .ToList(), 
        JsonRequestBehavior.AllowGet);
}

OutputCacheLocation.Client - Specifies that you want to cache the results on client only. There are other options available.

VaryByParam = "id;query" - Is needed to differ cache results based on method arguments.

Duration - cache duration in seconds.

Answer 2

You need some caching stratergies here is simple cache helper class

using System.Runtime.Caching;  

public class cacheservice: ICacheservice
{
    public T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class
    {
        T item = MemoryCache.Default.Get(cacheKey) as T;
        if (item == null)
        {
            item = getItemCallback();
            MemoryCache.Default.Add(cacheKey, item, DateTime.Now.AddMinutes(10));
        }
        return item;
    }
}

interface ICacheService
{
    T GetOrSet<T>(string cacheKey, Func<T> getItemCallback) where T : class;
}

Usage:

cacheservice.GetOrSet("CACHEKEY", (delegate method if cache is empty));

Cache provider will check if there's anything by the name of "CACHEKEY" in the cache, and if there's not, it will call a delegate method to fetch data and store it in cache.

Example:

var Data=cacheService.GetOrSet("CACHEKEY", ()=>SomeRepository.GetData());

In your case it would be like

var Data=cacheService.GetOrSet("CACHEKEY", Db.BusinessLine.AsQueryable()
            .Where(x => x.Label.Contains(query))
            .Take(10)
            .Select(x => new { id = x.BusinessLineId, text = x.Label })
            .ToList());

You can customize according to your needs as well

Using these caching strategies it will first time load data and store in cache in second time it will get value from cache instead of round trip to database.