Skip to main content

Kendo MVC Grid DataSourceRequest with AutoMapper - Advance

The actual process to make DataSourceRequest compatible with AutoMapper was explained in my previous post Kendo MVC Grid DataSourceRequest with AutoMapper, where we had created custom model binder attribute and in that property names were changed as data models.

In this post we will be looking into using AutoMapper's Queryable extension to retrieve the results based on selected columns. When Mapper.Map<RoleViewModel>(data) is called it retrieves all column values from table. The Queryable extension provides a way to retrieve only selected columns from table. In this particular case based on properties of RoleViewModel.

The previous approach that we implemented is perfect as far as this article (3 Tips for Using Telerik Data Access and AutoMapper) is concern about performance where it states:
While this functionality allows you avoid writing explicit projection in to your LINQ query it has the same fatal flaw as doing so - it prevents the query result from being cached.
Since this can have a strong negative impact on the performance even though only minimal amount of data is retrieved, we advise you not to use AutoMapper projection in LINQ queries. Instead we recommend you map the instances of your persistent types after they have been completely retrieved in memory using the Map method of AutoMapper.
I am not against or in favour of any approach it all depends on requirement. If we have tables with large number of columns then it won't be good approach. So, if you plan to go with AutoMapper extension for projection then only follow ahead.

ToDataSourceResult is an extension method from Kendo, which internally takes care of projection with different sorts, filters, groups and aggregates. We need all these features except the projection that need to handled by us using AutoMapper. The ToDataSourceResult uses "Kendo.Mvc.Extensions.CreateDataSourceResult" function to form mentioned features. 

This is a only part of code that we need to implement for having AutoMapper Linq Projection:

     /// <summary>  
     /// Creates the data source result.  
     /// </summary>  
     /// <typeparam name="TModel">The type of the model.</typeparam>  
     /// <typeparam name="TResult">The type of the result.</typeparam>  
     /// <param name="queryable">The queryable.</param>  
     /// <param name="request">The request.</param>  
     /// <returns>Kendo Data source result</returns>  
     /// <remarks>MODIFICATION OF "Kendo.Mvc.Extensions.CreateDataSourceResult" TO IMPLEMENT AUTOMAPPER PROJECTION.</remarks>  
     public static DataSourceResult CreateDataSourceResult<TModel, TResult>(this IQueryable<TModel> queryable, DataSourceRequest request)  
     {  
       Func<AggregateDescriptor, IEnumerable<AggregateFunction>> aggregates = null;  
       var dataSourceResult = new DataSourceResult();  
       IQueryable queryables = queryable;  
       var filterDescriptors = new List<IFilterDescriptor>();  
       if (request.Filters != null)  
       {  
         filterDescriptors.AddRange(request.Filters);  
       }  
       if (filterDescriptors.Any<IFilterDescriptor>())  
       {  
         queryables = queryables.Where(filterDescriptors);  
       }  
       var sortDescriptors = new List<SortDescriptor>();  
       if (request.Sorts != null)  
       {  
         sortDescriptors.AddRange(request.Sorts);  
       }  
       var sortDescriptors1 = new List<SortDescriptor>();  
       var groupDescriptors = new List<GroupDescriptor>();  
       if (request.Groups != null)  
       {  
         groupDescriptors.AddRange<GroupDescriptor>(request.Groups);  
       }  
       var aggregateDescriptors1 = new List<AggregateDescriptor>();  
       if (request.Aggregates != null)  
       {  
         aggregateDescriptors1.AddRange(request.Aggregates);  
       }  
       if (aggregateDescriptors1.Any<AggregateDescriptor>())  
       {  
         IQueryable queryables1 = queryables.AsQueryable();  
         IQueryable queryables2 = queryables1;  
         if (filterDescriptors.Any<IFilterDescriptor>())  
         {  
           queryables2 = queryables1.Where(filterDescriptors);  
         }  
         dataSourceResult.AggregateResults = queryables2.Aggregate(aggregateDescriptors1.SelectMany<AggregateDescriptor, AggregateFunction>((AggregateDescriptor a) => a.Aggregates));  
         if (groupDescriptors.Any<GroupDescriptor>() && aggregateDescriptors1.Any<AggregateDescriptor>())  
         {  
           groupDescriptors.Each<GroupDescriptor>((GroupDescriptor g) =>  
           {  
             AggregateFunctionCollection aggregateFunctions = g.AggregateFunctions;  
             List<AggregateDescriptor> aggregateDescriptors = aggregateDescriptors1;  
             if (aggregates == null)  
             {  
               aggregates = (AggregateDescriptor a) => a.Aggregates;  
             }  
             aggregateFunctions.AddRange<AggregateFunction>(aggregateDescriptors.SelectMany<AggregateDescriptor, AggregateFunction>(aggregates));  
           });  
         }  
       }  
       dataSourceResult.Total = queryables.Count();  
       if (groupDescriptors.Any<GroupDescriptor>())  
       {  
         groupDescriptors.Reverse<GroupDescriptor>().Each<GroupDescriptor>((GroupDescriptor groupDescriptor) =>  
         {  
           SortDescriptor sortDescriptor3 = new SortDescriptor()  
           {  
             Member = groupDescriptor.Member,  
             SortDirection = groupDescriptor.SortDirection  
           };  
           sortDescriptors.Insert(0, sortDescriptor3);  
           sortDescriptors1.Add(sortDescriptor3);  
         });  
       }  
       if (sortDescriptors.Any<SortDescriptor>())  
       {  
         queryables = queryables.Sort(sortDescriptors);  
       }  
       IQueryable queryables3 = queryables;  
       queryables = queryables.Page(request.Page - 1, request.PageSize);  
       if (groupDescriptors.Any<GroupDescriptor>())  
       {  
         queryables = queryables.GroupBy(queryables3, groupDescriptors);  
       }  
       dataSourceResult.Data = (queryables as IQueryable<TModel>).Execute<TModel, TResult>();  
       sortDescriptors1.Each<SortDescriptor>((SortDescriptor sortDescriptor) => sortDescriptors.Remove(sortDescriptor));  
       return dataSourceResult;  
     }  
     /// <summary>  
     /// Executes the specified source.  
     /// </summary>  
     /// <typeparam name="TModel">The type of the model.</typeparam>  
     /// <typeparam name="TResult">The type of the result.</typeparam>  
     /// <param name="source">The source.</param>  
     /// <returns></returns>  
     /// <exception cref="System.ArgumentNullException">source</exception>  
     /// <remarks>MODIFICATION OF "Kendo.Mvc.Extensions.Execute" TO IMPLEMENT AUTOMAPPER PROJECTION.</remarks>  
     private static IEnumerable Execute<TModel, TResult>(this IQueryable<TModel> source)  
     {  
       if (source == null)  
       {  
         throw new ArgumentNullException("source");  
       }  
       Type elementType = source.ElementType;  
       if (elementType != typeof(AggregateFunctionsGroup))  
       {  
         return source.Project().To<TResult>();  
       }  
       // TODO: Need to test with grouping  
       List<AggregateFunctionsGroup> aggregateFunctionsGroups = new List<AggregateFunctionsGroup>();  
       foreach (AggregateFunctionsGroup aggregateFunctionsGroup in source as IQueryable)  
       {  
         var aggregateQuerable = aggregateFunctionsGroup.Items.AsQueryable() as IQueryable<TModel>;  
         if (aggregateQuerable != null)  
         {  
           aggregateFunctionsGroup.Items = aggregateQuerable.Execute<TModel, TResult>();  
           aggregateFunctionsGroups.Add(aggregateFunctionsGroup);  
         }  
       }  
       return aggregateFunctionsGroups;  
     }  

If we see above code we only have two functions but both of them are having same code as whatever Kendo is providing with very few changes. The CreateDataSourceResult function is responsible for different sorts, filters, groups and aggregates but the actual call is happening under Execute function. To implement AutoMapper Linq Projection we only needed to modify Execute function but since it is only through CreateDataSourceResult, we need to modify both.

This is return source.Project().To<TResult>(); only change done under Execute function for mapping.

NOTE: I have not tested it with grouping. Possibly that might be the reason, Kendo did not provided some kind injection for mapping.

After that being setup we only need to call in this way.

 queryable.CreateDataSourceResult<RoleDomainModel, RoleViewModel>(request)  
 // Another example
 UnitOfWork.RoleRepository.All().CreateDataSourceResult<RoleDomainModel, RoleViewModel>(request);  

If you want, we can have similar implementation like Kendo by creating our own version of extension method ToDataSourceResult which can consume our created functions.


Comments

Popular posts from this blog

Elegantly dealing with TimeZones in MVC Core / WebApi

In any new application handling TimeZone/DateTime is mostly least priority and generally, if someone is concerned then it would be handled by using DateTime.UtcNow on codes while creating current dates and converting incoming Date to UTC to save on servers. Basically, the process is followed by saving DateTime to UTC format in a database and keep converting data to native format based on user region or single region in the application's presentation layer. The above is tedious work and have to be followed religiously. If any developer misses out the manual conversion, then that area of code/view would not work. With newer frameworks, there are flexible ways to deal/intercept incoming or outgoing calls to simplify conversion of TimeZones. These are steps/process to achieve it. 1. Central code for storing user's state about TimeZone. Also, central code for conversion logic based on TimeZones. 2. Dependency injection for the above class to ...

Using Redis distributed cache in dotnet core with helper extension methods

Redis cache is out process cache provider for a distributed environment. It is popular in Azure Cloud solution, but it also has a standalone application to operate upon in case of small enterprises application. How to install Redis Cache on a local machine? Redis can be used as a local cache server too on our local machines. At first install, Chocolatey https://chocolatey.org/ , to make installation of Redis easy. Also, the version under Chocolatey supports more commands and compatible with Official Cache package from Microsoft. After Chocolatey installation hit choco install redis-64 . Once the installation is done, we can start the server by running redis-server . Distributed Cache package and registration dotnet core provides IDistributedCache interface which can be overrided with our own implementation. That is one of the beauties of dotnet core, having DI implementation at heart of framework. There is already nuget package available to override IDistributedCache i...

Handling JSON DateTime format on Asp.Net Core

This is a very simple trick to handle JSON date format on AspNet Core by global settings. This can be applicable for the older version as well. In a newer version by default, .Net depends upon Newtonsoft to process any JSON data. Newtonsoft depends upon Newtonsoft.Json.Converters.IsoDateTimeConverter class for processing date which in turns adds timezone for JSON data format. There is a global setting available for same that can be adjusted according to requirement. So, for example, we want to set default formatting to US format, we just need this code. services.AddMvc() .AddJsonOptions(options => { options.SerializerSettings.DateTimeZoneHandling = "MM/dd/yyyy HH:mm:ss"; });

Trim text in MVC Core through Model Binder

Trimming text can be done on client side codes, but I believe it is most suitable on MVC Model Binder since it would be at one place on infrastructure level which would be free from any manual intervention of developer. This would allow every post request to be processed and converted to a trimmed string. Let us start by creating Model binder using Microsoft.AspNetCore.Mvc.ModelBinding; using System; using System.Threading.Tasks; public class TrimmingModelBinder : IModelBinder { private readonly IModelBinder FallbackBinder; public TrimmingModelBinder(IModelBinder fallbackBinder) { FallbackBinder = fallbackBinder ?? throw new ArgumentNullException(nameof(fallbackBinder)); } public Task BindModelAsync(ModelBindingContext bindingContext) { if (bindingContext == null) { throw new ArgumentNullException(nameof(bindingContext)); } var valueProviderResult = bindingContext.ValueProvider.GetValue(bin...

Architecture solution composting Repository Pattern, Unit Of Work, Dependency Injection, Factory Pattern and others

Project architecture is like garden, we plant the things in certain order and eventually they grow in similar manner. If things are planted well then they will all look(work) great and easier to manage. If they grow as cumbersome it would difficult to maintain and with time more problems would be happening in maintenance. There is no any fixed or known approach to decide project architecture and specially with Agile Methodology. In Agile Methodology, we cannot predict how our end products will look like similarly we cannot say a certain architecture will fit well for entire development lifespan for project. So, the best thing is to modify the architecture as per our application growth. I understand that it sounds good but will be far more problematic with actual development. If it is left as it is then more problems will arise with time. Just think about moving plant vs a full grown tree. Coming to technical side, In this article, I will be explaining about the various techniques ...

Making FluentValidation compatible with Swagger including Enum or fixed List support

FluentValidation is not directly compatible with Swagger API to validate models. But they do provide an interface through which we can compose Swagger validation manually. That means we look under FluentValidation validators and compose Swagger validator properties to make it compatible. More of all mapping by reading information from FluentValidation and setting it to Swagger Model Schema. These can be done on any custom validation from FluentValidation too just that proper schema property has to be available from Swagger. Custom validation from Enum/List values on FluentValidation using FluentValidation.Validators; using System.Collections.Generic; using System.Linq; using static System.String; /// <summary> /// Validator as per list of items. /// </summary> /// <seealso cref="PropertyValidator" /> public class FixedListValidator : PropertyValidator { /// <summary> /// Gets the valid items /// <...

Using LINQ to Entity efficiently with First/FirstOrDefault/Last/LastOrDefault/Single/SingleOrDefault

We generally use these extension methods First/FirstOrDefault/Last/LastOrDefault/Single/SingleOrDefault with predicates like ctx=> ctx.Model.FirstOrDefault(item => item.Id == 1 ) Or ctx=> ctx.Model.Where(item => item.Id == 1 ).FirstOrDefault() What is the problem with these? FirstOrDefault or similar methods immediately loads all data at once. So, let's say we have fifty columns on table then all those columns data would be retrieved from DB and saved into memory. This link gives a fair idea of different function behavior.  https://msdn.microsoft.com/en-us/library/bb882641.aspx .  So, even if we require only one value from selected field it retrieves all values. What is the solution? The solution is pretty simple. Whenever we need selected items better to do projection before calling FirstOrDefault or similar methods. Ex: Selecting single item ctx.Model.Where(itm => itm.Id == 1) .Select(itm => itm.Name).FirstO...

LDAP with ASP.Net Identity Core in MVC with project.json

Lightweight Directory Access Protocol (LDAP), the name itself explain it. An application protocol used over an IP network to access the distributed directory information service. The first and foremost thing is to add references for consuming LDAP. This has to be done by adding reference from Global Assembly Cache (GAC) into project.json "frameworks": { "net461": { "frameworkAssemblies": { "System.DirectoryServices": "4.0.0.0", "System.DirectoryServices.AccountManagement": "4.0.0.0" } } }, These  System.DirectoryServices  and  System.DirectoryServices.AccountManagement  references are used to consume LDAP functionality. It is always better to have an abstraction for irrelevant items in consuming part. For an example, the application does not need to know about PrincipalContext or any other dependent items from those two references to make it extensible. So, we can begin wi...

Channel, ChannelReader and ChannelWriter to manage data streams in multi-threading environment

I came across Channel class while working with SignalR which looks really interesting. By looking into NuGet packages ( https://www.nuget.org/packages/System.Threading.Channels ), it seems just 4 months old. The Channel class provides infrastructure to have multiple reads and write simuletensely through it's Reader and Writer properties. This is where it is handy in case of SignalR where data streaming needs to be done but is not just limited to that but wherever something needs to be read/write/combination of both in a multi-threading environment. In my case with SignalR, I had to stream stock data at a regular interval of time. public ChannelReader<StockData> StreamStock() { var channel = Channel.CreateUnbounded<StockData>(); _stockManager.OnStockData = stockData => { channel.Writer.TryWrite(stockData); }; return channel.Reader; } The SignalR keeps return type of ChannelReader<StockData> open so that whatev...

Blazor 0.5.0 Interop JavaScript from C# and C# to JavaScript call

Blazor provides two-way communication from JS to C# and C# to JS which is called Interop. The version upgrade to Blazor 0.5.0 changed the approach in interactions between cshtml and JS files. The newer version simplifies JS calling by avoiding pre-registration of JS function. In this article, we would see how to call a JS method by passing multiple parameters from cshtml and parameterized call from JS to cshtml. The scenario that is used in this article has a Kendo AutoComplete to search book and populate information based on the selection. An example of a call to JS from cshtml await JSRuntime.Current.InvokeAsync<string>( "searchBook.Init", "#SearchTitle", new DotNetObjectRef(this)); Takeaways from the above example: - JSRuntime.Current give environment to execute out-process JS. - InvokeAsync is a function that would allow executing the JS function. - The searchBook.Init is a JS function call, we would see it in details in the second sec...