Skip to main content

Easy way to parse SQL data reader objects

Many a times, I have seen that people end up writing lot of codes to read from SQL data reader or there is no fail safe mechanism to handle, if parse fails out.

In this article, I will try to cover up above issue and implement uniform way to handle things with fail safe mechanism using TryParse approach. Mainly, I will extend inbuilt try parse mechanism comes with .Net. Int.TryParse and similar type of methods was introduced in 2.0 Framework, so the code should be compatible with 2.0 or higher framework.

Let's directly dive into usage since we have just single function DbTryParse. I will be explaining function on later stage.
We can use with fail safe mechanism where some values are not properly parsed then row will get skipped or in normal way, we define some default value and move ahead with other rows.

 int id;  
 string val;  
 double dbl;  
 reader["id"].DbTryParse(out id, int.TryParse, 89);  
 reader["val"].DbTryParse(out val, "NA");  
 reader["doubleTest"].DbTryParse(out dbl, double.TryParse);  

I have tried with integer, string and double in similar way other types of variable can be used as well.
In this, I am reading integer Id column and sending logic for parsing with int.TryParse. If parse fails then it will set 100 as a default, this is optional parameter. Check out double parsing where we are not setting the default value.

Since we do not have inbuilt function like TryParse for string and it's a reference type. There is no need of handler and it is implemented in different way that we will see it later.

 reader["val"].DbTryParse(out val, "NA");  

If we want to skip rows on failure of any parse, then we could use:

 if (reader["id"].DbTryParse(out id, int.TryParse) &&  
 reader["val"].DbTryParse(out val) &&  
 reader["doubleTest"].DbTryParse(out dbl, double.TryParse))  
 {  
     Console.WriteLine("Parsing successful");  
 }  
 else  
 {  
     Console.WriteLine("Parsing failed.");  
 }  

That is all we need for parsing. The single DbTryParse is taking care of every possible parses.

Let's look into the implementation part. If we see all TryParse from .Net they accept string as first parameter and then the out parameter to parse value. For that a TryParseHandler<T> delegate wrapper is created. The generic parse functions are restricted with struct type which takes care of value type. The same function is overloaded to handle string type.

Here are codes:

   public static class CommonExtensionMethods  
   {  
     /// <summary>  
     /// Try parse handler  
     /// </summary>  
     /// <typeparam name="T">The result type</typeparam>  
     /// <param name="value">The string literal.</param>  
     /// <param name="result">The result of typecasting.</param>  
     /// <returns>True, if typecasting is successful, else false.</returns>  
     public delegate bool TryParseHandler<T>(string value, out T result);  
     /// <summary>  
     /// Generic try parse.  
     /// </summary>  
     /// <typeparam name="T">Type of the value</typeparam>  
     /// <param name="value">The string literal.</param>  
     /// <param name="parsedValue">The parsed value.</param>  
     /// <param name="handler">The type casting handler.</param>  
     /// <param name="defaultValue">The default value. This value will be set in case of failed parsing.</param>  
     /// <returns>Parsed object</returns>  
     /// <exception cref="System.ArgumentNullException">handler</exception>  
     public static bool TryParse<T>(this string value, out T parsedValue, TryParseHandler<T> handler,  
       T defaultValue = default(T))  
       where T : struct  
     {  
       if (handler == null)  
       {  
         throw new ArgumentNullException("handler");  
       }  
       if (String.IsNullOrEmpty(value))  
       {  
         parsedValue = defaultValue;  
         return false;  
       }  
       return handler(value, out parsedValue);  
     }  
     /// <summary>  
     /// Generic try parse for databases object.  
     /// </summary>  
     /// <typeparam name="T">The type of object for parsing value</typeparam>  
     /// <param name="val">The value.</param>  
     /// <param name="parsedValue">The parsed value.</param>  
     /// <param name="handler">The parsing handler.</param>  
     /// <param name="defaultValue">The default value. This value will be set in case of failed parsing.</param>  
     /// <returns>  
     /// Parsed object  
     /// </returns>  
     public static bool DbTryParse<T>(this object val, out T parsedValue, TryParseHandler<T> handler  
       , T defaultValue = default(T))  
       where T : struct  
     {  
       if (val == DBNull.Value)  
       {  
         parsedValue = defaultValue;  
         return false;  
       }  
       return Convert.ToString(val).TryParse(out parsedValue, handler, defaultValue);  
     }  
     /// <summary>  
     /// Databases object parsing to string.  
     /// </summary>  
     /// <param name="val">The value.</param>  
     /// <param name="parsedValue">The parsed value.</param>  
     /// <param name="defaultValue">The default value. This value will be set in case of failed parsing.</param>  
     /// <returns>String representation of parsed object</returns>  
     public static bool DbTryParse(this object val, out string parsedValue  
       , string defaultValue = null)  
     {  
       if (val == DBNull.Value)  
       {  
         parsedValue = defaultValue;  
         return false;  
       }  
       parsedValue = Convert.ToString(val) ?? defaultValue;  
       return parsedValue == defaultValue ? false : true;  
     }  
     /// <summary>  
     /// Databases object parsing to string.  
     /// </summary>  
     /// <param name="val">The value.</param>  
     /// <param name="defaultValue">The default value. This value will be set in case of failed parsing.</param>  
     /// <returns>String representation of given object</returns>  
     public static string DbParse(this object val, string defaultValue = null)  
     {  
       return val == DBNull.Value ? defaultValue : Convert.ToString(val) ?? defaultValue;  
     }  
   }  

Source: http://www.mindfiresolutions.com/Database-Reader-Object-Parsing-in-NET-2673.php

Comments

Popular posts from this blog

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 /// <...

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...

Kendo MVC Grid DataSourceRequest with AutoMapper

Kendo Grid does not work directly with AutoMapper but could be managed by simple trick using mapping through ToDataSourceResult. The solution works fine until different filters are applied. The problems occurs because passed filters refer to view model properties where as database model properties are required after AutoMapper is implemented. So, the plan is to intercept DataSourceRequest  and modify names based on database model. To do that we are going to create implementation of  CustomModelBinderAttribute to catch calls and have our own implementation of DataSourceRequestAttribute from Kendo MVC. I will be using same source code from Kendo but will replace column names for different criteria for sort, filters, group etc. Let's first look into how that will be implemented. public ActionResult GetRoles([MyDataSourceRequest(GridId.RolesUserGrid)] DataSourceRequest request) { if (request == null) { throw new Argume...

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...

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...

Custom SPA engine, similar to MVC pattern by using TypeScript

Single Page Application, a fundamental requirement for SPA is to develop the application with XMLHttpRequest (XHR) or AJAX. That is only main requirement, other things come as add-on stuff. Advancements of SPA? In today's world, we do not want to be restricted with basic features or functionalities. We want everything like any new Phone comes in market with some new shiny feature. There are a lot of functionalities available with SPA libraries and could be extended with more extension to have richer and easier implementation. To be specific we shall refer it as frameworks, not libraries. Earlier days one-way, two-way data binding with templates were very minimum things to expect from frameworks. Now they talk about component structure, Virtual Dom, IOC, state management, performance etc. Why building own framework/library? What I believe and experienced is each SPA JS Frameworks has its own set of rules and structure that has to be followed. If we want to have our own dyn...

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 ...

Configuring Ninject, Asp.Net Identity UserManager, DataProtectorTokenProvider with Owin

It can be bit tricky to configure both Ninject and Asp.Net Identity UserManager if some value is expected from DI to configure UserManager. We will look into configuring both and also use OwinContext to get UserManager. As usual, all configuration need to be done on Startup.cs. It is just a convention but can be used with different name, the important thing is to decorate class with following attribute to make it Owin start-up: [assembly: OwinStartup(typeof(MyProject.Web.Startup))] Ninject configuration Configuring Ninject kernel through method which would be used to register under Owin. Startup.cs public IKernel CreateKernel() { var kernel = new StandardKernel(); try { //kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>(); // TODO: Put any other injection which are required. return kernel; } catch { kernel.Dispose(); thro...