What is Blazor and Why should you Use it!

According to Microsoft Docs, Blazor is a framework for building client-side web UI with .NET. It’s a feature of ASP.NET, the popular web development framework that extends the .NET developer platform with tools and libraries for building web apps.

Blazor lets you build interactive web UIs using C# instead of JavaScript. Blazor apps are composed of reusable web UI components implemented using C#, HTML and CSS. Both client and server code is written in C#, allowing  you to share code and libraries across projects.

If you’ve done any client-side development, I’m assuming you are familiar with Vue, Angular, React or Aurelia. Each one of these technologies is built on top of JavaScript. Blazor is different, in that it allows a developer to build compelling UIs by leveraging your existing C#, HTML and CSS skills without writing a single line of JavaScript code. This sounds pretty amazing, correct?

What Browsers can my Blazor code run on?
All modern browsers have Web Assembly baked in on which your code runs. The browsers range from Chrome, IE, Edge, Safari including browsers on mobile devices.

Flavour of Blazor:
Blazor comes with two architectures:

  • Client-side Blazor (WebAssembly)
  •  Server-side Blazor

As of this writing, Server-side Blazor is the most stable release and can be used in production.

Client-side Blazor (WebAssembly) is still in preview and is likely to RTM mid-2020. The way it works is that when the application runs, it loads all assets such as static files, assemblies including the run-time which is later converted to WebAssembly bytecode without requiring a connection to the server. While it offers some advantages such as the non-dependence on the server for your hosting needs and also be able to work in offline scenarios. However, when it comes to jobs that require compute-intensive operation, then this architecture may not be suitable for your needs.

Server-side Blazor in my opinion does foot the bill easily as it conforms to the lowest common denominator. In another words, you are not restricted to just the latest modern browsers to run your server-side blazor code, but you can also have your code run on some of the older browsers that don’t have web assembly on them.

Furthermore, the server-side Blazor app runs inside ASP.NET runtime. Any changes to the app are copied using a WebSocket connection through SignalR. As a result, all updates are streamed from the server in real-time.

Does Blazor have Plugins?
Unlike Blazor’s predecessor technologies such as Flash and Silverlight that required plugins to be installed on the client’s machine, Blazor on the other hand does not require any plugins due to the fact that it runs in Web Assembly which is baked in every modern browser.

Advantages of Blazor:
Following are some of the advantages of Blazor:

  • Leverage your C# skills to build full-stack Web app
  • Reuse libraries that are .NET Standard compliant
  • Runs on .NET runtime
  • Runs on any browser
  • Doesn’t require any plugins
  • Download razor components from NuGet
  • Highly performant
  •  Runs at near-native speed inside the browser on WebAssembly
  • Allows interoperability between Blazor and JavaScript code

What Tools can I use to create Blazor Apps:
Blazor apps can be developed using Visual Studio 2019 (all versions) with .NET Core 3.1 SDK or alternatively you can use a free online tool called Visual Studio Code (with latest C# extension).
Blazor Code Snippet:

The above is a plain vanilla code that you get out of the box. It illustrates the use of C# and HTML. Although, when building an enterprise app, you would want to decouple your business logic in a separate class and restrict the razor component to HTML and CSS just to keep it clean and maintain a separation of concerns.

If you want to know more about Blazor, please use the following resources from Microsoft.


Posted in UI Framework | Leave a comment

How to Call a UDF using ADO.NET

Let’s face it, most of us typically work with Stored Procedures with modest complexity using JOINS and such. Some of us embed Common Table Expressions (CTE) in the stored procs.

If you are already using Entity Framework 2.2, you would know that stored procedures containing multiple joins is not fully supported unless it’s a SQL View in which case you would have to use DbQuery type in your DbContext class.

But, what if you have a UDF (scalar-valued function) and want to use it with ADO.NET!

Let’s see how it’s done. For the purposes of demonstration, let’s assume you have two tables: Department and Employee. Department has a one-to-many relationship with Employee, i.e. A Department can have one or more employees. This is illustrated in the Entity Relationship Diagram (ERD) below:











Next, let’s write a simple User Defined Function (UDF) which accepts @DepartmentID as an input parameter and returns the Employee Name.


	-- Add the parameters for the function here
	@DepartmentId INT
	-- Declare the return variable here
	DECLARE @EmployeeName NVARCHAR(50)

	-- Add the T-SQL statements to compute the return value here
	SELECT @EmployeeName = TRIM(FirstName) + ',' + TRIM(LastName)  
		DepartmentID = (SELECT DepartmentID 
						FROM Department 
						WHERE DepartmentID = @DepartmentId)

	-- Return the result of the function
	RETURN @EmployeeName


As a quick test, let’s test this function in SQL Management Studio. We can see when the function is invoked, it returns the Employee Name which is precisely what we want.







Now, let’s open Visual Studio and create a console application and write the following method. There are a couple of things that are worth noting.

  • Since this is not a stored procedure, the command type is defined as “CommandType.Text”. If you change it to “CommandType.StoredProcedure”, the program will compile. However, it will return a null value.
  • When newing up a Sql Command object, you must use the SELECT clause when declaring the function name and passing the required parameter to it i.e. “SELECT dbo.udf_GetEmployeeByID(@DepartmentId)”
  • Don’t forget to bring in the System.Data.SqlClient namespace. You can use NuGet for this.
  • Lastly, when invoking the ExecuteScalar() command, be sure to cast it to a string (in our case).
private static string GetEmployeeNameByID(int DepID)
            string retVal = string.Empty;
            using (SqlConnection connection = new SqlConnection(connStr))
                    using (SqlCommand cmd = new SqlCommand("SELECT dbo.udf_GetEmployeeByID(@DepartmentId)", connection))
                        cmd.CommandType = CommandType.Text;
                        cmd.Parameters.AddWithValue("@DepartmentID", DepID);
                        retVal = (string)cmd.ExecuteScalar();
                catch (SqlException ex)
                return retVal;

And now let’s put the code to test, by writing it out to a console.

static void Main(string[] args)

            string name = GetEmployeeNameByID(1);





Hope, you found this segment useful!

Posted in .NET, ADO.NET, SQL Server | Leave a comment

How to Enable .NET Core 3.0 Preview in VS2019

If you are in the process of creating a Blazor app in Visual Studio 2019 that you installed right after its launch (around April 2019 timeframe), chances are you’ll find the checkbox titled “Use previews of the .NET Core SDK” in the following location:

Tools -> Options -> Projects and Solutions -> .NET Core

However, if you’ve installed Visual Studio 2019 recently (as of this writing), the option has moved to the following location:

Tools -> Options -> Environment -> Preview Features.NET Core 3 Preview





Once the above is done, close Visual Studio IDE and open it again.

Now, Create a New Project and select ASP.NET Core Web Application template and hit ‘Next’, give a project name and hit ‘Next’ again and you’ll be presented with dialog with the option to select ASP.NET Core 3.0. Make sure you also select .NET Core on the LHS. This is a requirement for the successful creation of a Blazor app. (see image below).


Hope you found this post useful!


Posted in .NET | Leave a comment

Migrate SQL data to Azure Cosmos DB

Azure Cosmos DB

Azure Cosmos DB is a planet scale, JSON based schema free, No SQL database with multi-API support.

Microsoft defines it as a globally distributed, multi-model database service that supports document, key-value, wide-column and graph databases.

In this column, I’ll attempt to demonstrate what a cinch it is to import SQL data into Cosmos DB. Please note, the two are not the same. The analogy to describe the two is akin to a hammer vs. an axe. Just like you cannot use a hammer to chop down a tree, similarly, you cannot use an axe to drill a nail into the wall.

What do I need:

  • SQL Server Management Studio (SSMS)
  • Azure Cosmos DB Data Migration Tool
  •  Azure Cosmos DB Emulator

Azure Cosmos DB Data Migration Tool (DTUI)

DTUI is a data migration tool that is an open source solution used to import data to Azure Cosmos DB from a variety of sources that include the following:

  1.  JSON files
  2.  Mongo DB
  3.  SQL Server
  4.  CSV files
  5.  Azure Table Storage
  6.  Dynamo DB
  7.  HBase

Azure Cosmos DB Emulator

According to Microsoft docs, the Azure Cosmos Emulator provides a high-fidelity emulation of the Azure Cosmos DB service. It supports identical functionality as Azure Cosmos DB, including support for creating and querying data, provisioning and scaling containers, and executing stored procedures and triggers. You can develop and test applications using the Azure Cosmos Emulator, and deploy them to Azure at global scale by just making a single configuration change to the connection endpoint for Azure Cosmos DB.

To download and install the Azure Cosmos Emulator, you can use this link.

Migrating Data

To migrate SQL data, we would need data. For the purposes of demonstration, I am using Adventure Works database, a Microsoft sample database that you can download here.

The Process

Let’s open SSMS and use one of the Views. A typical View is created by joining multiple related tables together. The View that is being used in this example is Purchasing.vVendorWithAddresses, where Purchasing is the name of the schema.

This View contains information about Vendor with Addresses in each row such that each of these rows can be mapped to a self-contained JSON document once the migration completes. Notice the column names that are defined as aliases. There’s also a “.” which is used as a separator to split address into address type, city, location etc. In other words, this will help shape the JSON document to transform each row into a complex JSON document instead of a flat document containing simple properties.

Although the “.” is irrelevant to SQL, however, it is used to tell the migration tool how to shape the documents that are being imported.

	CAST(BusinessEntityID AS VARCHAR) AS [id], 
	[Name] AS [name],
	AddressType AS [address.addressType], 
	AddressLine1 AS [address.addressLine1], 
	AddressLine2 AS [address.addressLine2], 
	City AS [address.city], 
	StateProvinceName AS [address.location.stateProvinceName], 
	PostalCode AS [address.postalCode], 
	CountryRegionName AS [address.countryRegionName]

The next thing you want to do is to open the Migration Tool utility and start configuring.

Source Info

Here you will specify the API to import from, connection string, query and the nesting separator. See image below:

Target Info

Use the Azure Cosmos DB Emulator to copy the connection string (circled in red above).

One of the things you ought to keep in mind when creating a container is to define its partition key. Typically, this is a property you choose that will help scale your data both in terms of storage and throughput.

In our case, we have chosen “/address/postalCode” as the partition key.

Note: It may be noted that the name of the column defined in SQL query is case-sensitive in order for it to be recognized when transforming the query results into Cosmos DB documents.

When you click Next, you’ll be presented with an Advanced tab. Skip this section by clicking Next. 

Now you will be on the Summary page where you can review all that you have configured in the previous steps. Once you are sure, click the Import button.

The tool will import the records and transform them to documents. In this case 104 of them. See below:


Now, let’s flip over to Azure Cosmos DB Emulator. Refresh the page and you’ll see the newly Created Database, Collection and Documents. See below:


Query the Data:

With the power of SQL API that Cosmos DB supports, you can query your data just as you would if you were in SSMS. See the query below:













Here, we saw the use of SQL API and how it can be used to model data as JSON documents. We made use of a view in SQL database, massaged it and transformed the SQL records into Cosmos DB documents following some easy steps.


  1.  Azure Cosmos DB
  2. Azure Cosmos DB Data Migration Tool



Posted in NoSQL | Leave a comment

Entity Framework Core 3.0 Preview 4

Diego Vega, the Program Manager of the Entity Framework team recently announced on his blog some of the breaking changes in ASP.NET Core 3.0 Preview 4.

Some of these changes include the following:

  • LINQ queries are no longer evaluated on the client
  • EF Core runtime no longer part of the ASP.NET Core shared framework. In other words, they have to be obtained via NuGet package
  • DotNet EF Tool is no longer part of the .NET Core SDK. It has to be downloaded separately
  • Automatic key generation (reset) after in-memory database is deleted
  • Database connection no longer remains open until a TransactionScope is disposed
  • The concept of query types has been renamed to entities without keys
  • New preview of the Cosmos DB provider for EF Core.  Some of the changes include the usage of deterministic appraoch to key generation and allowing developer to specify Azure region to us. Fantastic!!!
  • EF 6.3 to target .NET Standard 2.1, in addition to already supported .NET Framework versions.


Posted in ORM | Leave a comment

Cannot connect to runtime process, timeout after 10000 ms

If you are a web developer, it’s given that you also write JavaScript code.

I am building an ASP.NET Core app in VS 2017 and I needed to install a feature that I chose to write in JavaScript. While everything worked fine initially, however, when I stopped the app and re-ran it, I got a nasty error. See image below:

I decided to shut down Visual Studio, launched it and open my project, but still in vain.

Turned out that in Tools => Option => Debugging => General, there is an item (circled in red) i.e. Enable JavaScript debugging for ASP.NET (Chrome, Edge and IE).

After unchecking this item and running the app, everything appeared just fine.

I certainly don’t recommend this to be a solution, but rather a workaround. Meanwhile, you can use developer tools in your favorite browser and continue debugging. Alternatively, you can also launch Visual Studio 2017 and select “Run as administrator.”

Posted in Uncategorized | Leave a comment

Query Types in EF Core

If you have been using Entity Framework 6.x or EF Core, then you are already familiar with Entities and its usage.

Query Types is a new addition to EF Core 2.1 which you can refer to Entities as its cousin.

What are some of the Use Cases

  • Is used when working with entities with no key propertie(s) defined, may it be a Table, Stored Procedure or a View
  • Is used when mapping to queries specified in the model
  • Is used for ad hoc queries where changes are not tracked in DbContext. In other words, queries that are strictly read-only

So let’s get Started

First let’s define the two POCO classes. Each of these classes below maps to the tables in the database.

public class BaseAggr
        public long BaseAggrId { get; set; }
        [Display(Name = "Portfolio ID")]
        public string PortfolioId { get; set; }

        [Display(Name = "Scenario ID")]
        public long? ScenarioId { get; set; }

        [Display(Name = "Sum Pnl")]
        public double? SumPnl { get; set; }

        [Display(Name = "Business Date")]
        public DateTime? BusinessDate { get; set; }
    public class WhatIfAggr
        public long WhatifAggrId { get; set; }

        [Display(Name="Portfolio ID")]
        public string PortfolioId { get; set; }

        [Display(Name ="Scenario ID")]
        public long? ScenarioId { get; set; }

        [Display(Name ="Sum PnL")]
        public double? SumPnl { get; set; }

        [Display(Name ="Business Date")]
        public DateTime? BusinessDate { get; set; }

Next, let’s create a database view. As you can tell from the query below that it’s using Common Table Expression to form a result set.

CREATE OR ALTER VIEW [dbo].[vwVarByPortfolios] AS
(SELECT portfolio_id, scenario_id as scenario_id, sum_pnl as var_pnl 
	FROM (SELECT portfolio_id,scenario_id, sum_pnl, RANK() OVER (PARTITION BY portfolio_id ORDER BY sum_pnl DESC) AS pnl_rank FROM base_aggr) AS Agg
	WHERE pnl_rank = 98
(SELECT portfolio_id AS wi_portfolio_id, scenario_id AS wi_scenario_id, sum_pnl AS wi_var_pnl 
	FROM (SELECT portfolio_id,scenario_id, sum_pnl, RANK() OVER (PARTITION BY portfolio_id ORDER BY sum_pnl desc) AS pnl_rank from whatif_aggr) AS Agg
	WHERE pnl_rank = 98
 ) AS X
 ON portfolio_id = wi_portfolio_id;

In addition to the classes above, you would also need a class for Query Type to hold results from the database view like so:

public class PortfolioView
public string PortfolioID { get; set; }
public long ScenarioID { get; set; }
public double VarPnl { get; set; }
public string WiPortfolioID { get; set; }
public long WiScenarioID { get; set; }
public double WiVarPnl { get; set; }

Next, we will create a DbQuery property in the DbContext class in order for it to be recognized as a query type.

public DbQuery PortfolioView { get; private set; }

Next, we will write a fluent API in DbConext’s OnModelCreating method to map the view to the Query Type i.e. vwVarByPortfolios. The “ToView” extension method is used to configure the mapping especially when a relational database is being targeted.

                .Property(p => p.PortfolioID).HasColumnName("portfolio_id");

                .Property(p => p.ScenarioID).HasColumnName("scenario_id");

                .Property(p => p.VarPnl).HasColumnName("var_pnl");

                .Property(p => p.WiPortfolioID).HasColumnName("wi_portfolio_id");

                .Property(p => p.WiScenarioID).HasColumnName("wi_scenario_id");

                .Property(p => p.WiVarPnl).HasColumnName("wi_var_pnl");

Please note, DbQuery does not require a primary key to be defined unlike its DbSet<T> counterpart. The Id’s are being used here just because they are needed.

What you cannot Do:

Couple things worth noting is that in this version i.e. EF Core 2.2, EF Core does not allow Views to be created in the database when migrations are run. Conversely, you cannot reverse engineer views yet. This will most likely be available in the future version of EF Core i.e. 3.0. Here’s the EF Core Roadmap in case you wish you know further.

Lastly, you can query the database view in your console app or a Web App, although in this case, the latter is being used along with Razor Pages.

 public class PortfolioModel : PageModel
        private readonly DataAggr.Models.DataAggrContext _context;

        public PortfolioModel(DataAggrContext context)
            _context = context;

        public IList PortfolioView { get; set; }

        public async Task OnGetAsync()
            PortfolioView = await _context.Query()

A quick snapshot of the output of the View from inside SQL Management Studio.

Output on a Razor Page in ASP.NET Core.

Hope you found the article useful!

Posted in .NET, ORM | Leave a comment

Data Seeding in EF Core

Data seeding is a process where you populate the initial set of data into the database. I’ll explain some of the rudimentary steps needed for creating seed data in your app.

Prior to EF Core 2.1, seeding data was not quite straight-forward. However with this version, you can seed data using the following steps:

  1. Download the necessary packages from NuGet
  2. Create your Context Class
  3. Write Seed Data
  4. Run Migrations
  5. Apply data changes to your database

Let’s begin…

Download Packages: You need the following packages after you create a new .NET Core console app:

  • Microsoft.EntityFrameworkCore
  • Microsoft.EntityFrameworkCore.SqlServer
  • Microsoft.EntityFrameworkCore.Tools

Context Class: Create a new context class which would derive from DbContext. DbContext represents a session with the database and is used to perform CRUD operations against your database. It’s also a combination of Unit of Work and Repository patterns.

public class DataSeedContext : DbContext
        public DbSet Blog { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
                @"server=obi-oberoi; database=demo.DotNetConf; trusted_connection=true;");
        protected override void OnModelCreating(ModelBuilder modelBuilder)
                .Property(u => u.Url)

                new Blog { BlogId = 1, Url = "http://ObiOberoi.com" },
                new Blog { BlogId = 2, Url = "http://microsoft.com" },
                new Blog { BlogId = 3, Url = "http://cnn.com" },
                new Blog {  BlogId = 4, Url = "https://yahoo.com"},
                new Blog { BlogId = 5, Url = "https://tesla.com" },
                new Blog { BlogId = 6, Url = "https://meetup.com/mississauganetug"},
                new Blog { BlogId = 7, Url="https://td.com"},
                new Blog { BlogId = 8, Url="https://meetup.com/TorontoNETUG"}

Create a Blog class like so:

public class Blog
        public int BlogId { get; set; }
        public string Url { get; set; }

Be sure to specify the type of database you wish to use. In the example, SQL Server is being used. This is defined in the Context class’s OnConfiguring method.

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
                @"server=obi-oberoi; database=demo.DotNetConf; trusted_connection=true;");

Run Migration: Just a quick overview of Migrations. Migrations allow you to keep your database in sync with your code. EF Core uses your mapping configurations to produce a snapshot of what your database should look like. Your model may represent tables, its primary keys, foreign keys, indexes, constraints and such.

Whenever you make a change to your POCO class i.e. add or remove a property, you ought to run a PowerShell command like so:

Add-Migration <migration name>

The Add-Migration command computes a database schema from your entity classes and scaffolds a migration with Up and Down methods which consists of the current version of the database to the new version it computes.

Apply Changes to Database: You do this by simply issuing the following command in PowerShell and you are set:


So, this was a quick intro to seeding data into the database.

Posted in .NET, ORM | Leave a comment

Import CSV into SQL Server using VBA

You have heard the famous cliché, “there are many ways to skin a cat”.

That said, there are many ways to import a flat file into SQL Server. Some of them include the following:

  • SSMS – Select Database -> Right Click Tasks -> Import Flat File
  • SQL Server Integration Services (SSIS)
  • Programmatically – Using your favourite language of choice (C# or VB.Net)
  • PowerShell
  • VBA

In this post I’m going to show the Power Users how you can leverage your VBA skills to write a simple Macro and then use it to import a flat file into SQL Server.

What You’ll Need

  1.  SQL Server Management Studio (download here for free)
  2.  Microsoft Excel (2010 or greater)

What are we working With

  • CSV file
  •  Database table

CSV File (this file contains about 15,000 records. For brevity, we are showing a dozen records).

drilldown_request_id dim_1 scenario_id dim_1_pnl
102 PROD_013 96 39.43999672
102 PROD_001 23 -63.47999954
102 PROD_011 4 -5.650003552
102 PROD_015 73 -3.210000992
102 PROD_014 21 19.40999985
102 PROD_014 71 -2.779999018
102 PROD_005 27 -123.8400006
102 PROD_010 2 -56.66000366
102 PROD_012 16 -37.25999832
102 PROD_008 58 -112.4700006
102 PROD_007 54 76.349998
102 PROD_007 44 88.24000001

Database Table Schema:

What Won’t Work

If you simply copy and paste records from the .csv file in SQL Management Studio and attempt to insert them, it would fail. That’s because, you need to stage the data by massaging it such that it is syntactically correct. This means wrapping single quotes i.e. (‘PROD_001 ‘) around every value in dim_1 column and separating each of the columns by comma (,). Now, with over 15000 records, this is next to impossible.

Use Macro in VBA

Open the .csv file in Excel like so.

Hit Alt-F11 to open VBA code surface. Here, simply write a Sub() method

Sub ImportData()
    On Error Resume Next
    Dim drillDownRequestId As Integer
    Dim dim1 As String
    Dim scenarioId As Integer
    Dim dim1Pnl As Double
    Dim sTemp As String
    Dim SQLScript As String
    Dim i As Integer
    For i = 2 To 15001
        drillDownRequestId = ThisWorkbook.Worksheets("drilldown_table").Range("A" & i).Value
        dim1 = ThisWorkbook.Worksheets("drilldown_table").Range("B" & i).Value
        scenarioId = ThisWorkbook.Worksheets("drilldown_table").Range("C" & i).Value
        dim1Pnl = ThisWorkbook.Worksheets("drilldown_table").Range("D" & i).Value
        SQLScript = "insert into drilldown values(" & drillDownRequestId & ",'" & dim1 & "'," & scenarioId & "," & dim1Pnl & ")"
        ThisWorkbook.Worksheets("drilldown_table").Range("F" & i).Value = SQLScript
    Next i
End Sub

Now, you can Hit F5 and have the program run all the way. It’ll probably take a second or so to process 15000 records.

Once the program has run successfully, examine the SQL Script in column F of your Excel spreadsheet. As a quick test, copy the script from a single cell and paste it into SSMS and run it. If the operation executes successfully, you know that the script is syntactically correct.

Alternatively, you can set a breakpoint in the For loop by pressing F9 and then hit F8 to step into the code.



Please remember there are different horses for different courses . Sometimes one situation doesn’t fit all. This blog post is intended for VBA power users/developers. Those of you that write code in other languages, but have not used VBA, this might be a good primer.

Hope you found this simple post useful 🙂


Posted in SQL Server | Leave a comment

How to create an .EXE using .NET Core Console App

In the previous exercise, we learnt how to publish and execute a .NET Core Console App! In case you want to review that exercise, you can access it from here.

In this exercise, we’ll look at a quick way to turn a .DLL to an .EXE. Please note, when you build a .NET Core console app, it compiles the app to a DLL.

Here’s I’ll show you how to create an EXE:

  • Go to the command prompt and navigate to the location where the project is stored
  • Issue the following command: dotnet build -r win10-x64

You’ll find the .EXE in the folder i.e. Win10-x64. See image below:

Hope this was helpful.

Posted in .NET | Comments Off on How to create an .EXE using .NET Core Console App