Step-by-Step Guide: Adding Swagger to a .NET Core Web API Latest Version

 Swagger to a .NET Core Web API project is a great way to document your API endpoints and allow developers to easily interact with your API. Here’s how you can add Swagger to your .NET Core Web API project:

1. Install the necessary NuGet packages:

Microsoft.AspNetCore.Mvc.Versioning
Swashbuckle.AspNetCore

2. In the ConfigureServices method of your Startup.cs file, add the following code:

services.AddApiVersioning(options =>
{
options.ReportApiVersions = true;
});

services.AddSwaggerGen(c =>
{
c.SwaggerDoc(“v1”, new OpenApiInfo { Title = “My API”, Version = “v1” });
});

This code enables API versioning and adds Swagger to your project.

3. In the Configure method of your Startup.cs file, add the following code:

app.UseSwagger();
app.UseSwaggerUI(c =>
{
c.SwaggerEndpoint(“/swagger/v1/swagger.json”, “My API V1”);
});

This code adds the Swagger UI to your project, which provides a user interface for interacting with your API.

4. Decorate your controller classes and methods with Swagger annotations to provide additional information about your API. For example:

[ApiController]
[Route(“api/[controller]”)]
[ApiVersion(“1.0”)]
[SwaggerTag(“Operations about Products”)]
public class ProductsController : ControllerBase
{
[HttpGet]
[SwaggerOperation(“GetAllProducts”)]
[SwaggerResponse(StatusCodes.Status200OK, “Success”, typeof(IEnumerable<Product>))]
[SwaggerResponse(StatusCodes.Status404NotFound, “Not Found”)]
public async Task<IActionResult> GetAllProducts()
{
// Code to get all products
}
}

In this example, the [SwaggerOperation] annotation provides a friendly name for the operation, and the [SwaggerResponse] annotations provide information about the possible responses to the operation.

5. Build and run your project, and navigate to /swagger to view the Swagger UI and interact with your API.

now have Swagger integrated into your .NET Core Web API project.

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how to establish a connection between a .NET Core Web API 3.1 application and a SQL Server database using the Dapper ORM?

1.     In your Startup.cs file, add the following code to the ConfigureServices method to register the connection string with the dependency injection container:

 

                Install-Package Dapper /* Run this command on package manager console */

2.     In your appsettings.json file, add a connection string for your SQL Server database. Here's an example:

 

"ConnectionStrings":

{

"MyDb": "Server=myserver;Database=mydatabase;User      Id=myusername;Password=mypassword;"

}

3.     In your Startup.cs file, add the following code to the ConfigureServices method to register the connection string with the dependency injection container:

 

services.AddScoped<IDbConnection>(c =>

    new SqlConnection(Configuration.GetConnectionString("MyDb")));

 

4.     In your controller or service class, inject the IDbConnection using constructor injection:

                private readonly IDbConnection _db;

                public MyController(IDbConnection db)

{

    _db = db;

}

 

5.     To execute a SQL query, you can use the Query or QueryAsync method of the IDbConnection object. Here's an example:

 

var customers = await _db.QueryAsync<Customer>("SELECT * FROM Customers");

 

In this example, we're selecting all the rows from the Customers table and mapping them to a list of Customer objects.

Write a SQL query to find the total revenue generated by each customer in the month of January 2022.

 Suppose you have a table called "orders" with the following columns: "order_id" (integer), "customer_id" (integer), "order_date" (date), and "total_price" (decimal). and we want to find out the total revenue generated by each customer in the month of Jan 2022.

Solution 1:

SELECT customer_id, SUM(total_price) AS total_revenue FROM orders WHERE order_date BETWEEN '2022-01-01' AND '2022-01-31' GROUP BY customer_id;

In this solution, we use the SUM() function to add up the "total_price" column for each customer, and the GROUP BY clause to group the results by customer_id. We also use the BETWEEN operator to filter the results to only include orders made in the month of January 2022. The resulting output will show the customer_id and the total revenue generated by each customer during that time period.

Solution 2:

SELECT customer_id, SUM(CASE WHEN order_date BETWEEN '2022-01-01' AND '2022-01-31' THEN total_price ELSE 0 END) AS total_revenue FROM orders GROUP BY customer_id;

This solution also calculates the total revenue generated by each customer in the month of January 2022. However, instead of using a WHERE clause to filter the data, it uses a CASE expression inside a SUM function to only include orders made within the specific time period. The GROUP BY clause groups the results by customer_id.

what is crawl request

 

A crawl request is a request made by a webmaster or website owner to a search engine's crawler to visit and crawl a specific web page or URL on their website.

Search engine crawlers (also known as spiders, bots or robots) are programs that scan the web, discovering and indexing new pages, and updating the search engine's index with new or updated content. When a website is crawled, the search engine's crawler visits the website and analyses the content of the pages to determine what the website is about and how relevant it is to specific search queries.

A crawl request can be useful for ensuring that a new or updated page on your website is indexed quickly by search engines. If you have made changes to a page that you want search engines to know about, you can submit a crawl request to the search engine so that it will visit the updated page and reindex it. This can help to ensure that the updated content is reflected in search results as quickly as possible.

It's worth noting that submitting a crawl request does not guarantee that the search engine will crawl your page immediately, but it can speed up the process. In general, search engines will crawl pages based on their own algorithms and schedule, so it's important to ensure that your website is optimized for search engines and that you regularly publish new and relevant content.

SQL Server practical question with a possible solution: Top 3 Highest salary

 

Suppose you have a table named "employees" with the following columns: employee_id (int), first_name (varchar), last_name (varchar), hire_date (datetime), and salary (decimal). Write an SQL query to retrieve the top 3 highest-paid employees in the table.

Solution 1: You can use the "TOP" and "ORDER BY" clauses to retrieve the highest-paid employees. Here's an example query:

 

SELECT TOP 3 first_name, last_name, salary

FROM employees

ORDER BY salary DESC;

 

This query selects the first_name, last_name, and salary columns from the "employees" table, and then sorts the results by the "salary" column in descending order. The "TOP 3" clause limits the results to the top 3 rows.

Note: If there are ties for the fifth highest salary, the query will return all employees with that salary. If you want to limit the results to exactly 3 rows, you can use the "SELECT DISTINCT TOP 3" syntax instead.

there are other ways to write the query to retrieve the top 3 highest-paid employees from the "employees" table in SQL Server. Here are a few alternative solutions:

Solution 2: Using Limit Clause:

 

SELECT first_name, last_name, salary

FROM employees

ORDER BY salary DESC

LIMIT 3;

Note : "LIMIT" clause is not supported in SQL Server, but it is supported in some other database management systems such as MySQL and PostgreSQL.

Solution 3: Using Sub-query:

SELECT first_name, last_name, salary FROM employees WHERE salary IN ( SELECT TOP 3 salary FROM employees ORDER BY salary DESC );

This query uses a subquery to retrieve the top 3 highest salaries, and then selects the first_name, last_name, and salary columns for the employees with those salaries. The "WHERE salary IN" clause filters the results to only include employees whose salary is in the top 3.

Solution No -4 : Using the "RANK" function:

SELECT first_name, last_name, salary FROM ( SELECT first_name, last_name, salary, RANK() OVER (ORDER BY salary DESC) AS salary_rank FROM employees ) AS ranked_employees WHERE salary_rank <= 3;

This query uses the "RANK" function to assign a rank to each employee based on their salary, with the highest salary being assigned a rank of 1. The outer query selects the first_name, last_name, and salary columns for employees whose salary rank is 1-3.

What is the Log Shipping in SQL Server?

Log shipping is a disaster recovery solution for SQL Server that involves copying and restoring transaction log backups from a primary database server to one or more secondary database servers. The purpose of log shipping is to maintain a warm standby database on a secondary server that can be quickly activated in the event of a primary server failure or disaster.

Here's how log shipping works:

1. On the primary server, transaction logs are backed up and copied to a shared location that is accessible by the secondary server.

2. On the secondary server, the transaction logs are restored to a standby database, which is kept in a recovery mode that allows additional transaction logs to be applied as they become available.

3. The secondary database can be configured to stay in a read-only state or in standby mode, which allows users to query the database, but not modify it.

4. In the event of a primary server failure or disaster, the secondary database can be activated, and users can begin using it for read and write operations.

Log shipping provides a relatively low-cost disaster recovery solution for SQL Server, as it requires only standard backup and restore operations, and can be configured with built-in SQL Server functionality. However, log shipping does have some limitations, such as the potential for data loss if the transaction log backups are not frequent enough, and the need for manual failover and failback operations. As such, log shipping is typically used in conjunction with other disaster recovery solutions, such as clustering or Always On Availability Groups.

 

SQL Server Basic problems

 Here are a few common SQL Server problems and their solutions:

1. Slow performance: One of the most common SQL Server problems is slow performance. This can be caused by a number of factors, including insufficient memory or disk space, inefficient queries, or a poorly designed database schema. To address this problem, you can try optimizing your queries, indexing your database, or upgrading your hardware.

2. Database corruption: If your database becomes corrupt, you may be unable to access your data. To address this problem, you can try restoring from a backup, repairing the database using the DBCC CHECKDB command, or using a third-party recovery tool.

3. Connection issues: If you're having trouble connecting to your SQL Server instance, it could be due to a firewall or network issue, an incorrect login or password, or a misconfigured server. To address this problem, you can check your firewall settings, double-check your login credentials, or try restarting the SQL Server service.

4. Deadlocks: Deadlocks occur when two or more processes are blocked, waiting for each other to release a resource. To address this problem, you can try optimizing your queries to reduce contention, or implementing locking hints to control concurrency.

5. Insufficient disk space: If you run out of disk space on your SQL Server instance, you may be unable to insert or update data. To address this problem, you can try deleting unnecessary data, archiving old data to a separate server, or adding more disk space to your server.

Asynchronous programming in javascript with example

 Asynchronous programming in JavaScript is a way to execute non-blocking code, allowing other parts of the program to continue running while waiting for a long-running operation to complete. Here's an example of asynchronous programming in JavaScript using callbacks:

function getData(callback) { // Simulate a long-running operation with setTimeout setTimeout(function() { const data = [1, 2, 3, 4, 5]; callback(data); }, 1000); } function displayData(data) { console.log(data); } // Call getData with displayData as a callback function getData(displayData); console.log("This code is executed before the data is retrieved.");

In this example, the getData function simulates a long-running operation using setTimeout, and takes a callback function as an argument. Once the operation is complete, getData calls the callback function with the resulting data.

The displayData function is defined as a separate function to handle the data once it is retrieved. This function is passed as a callback to getData.

Finally, getData is called with displayData as the callback function, and the program continues running while the data is retrieved. The last console.log statement is executed before the data is retrieved, demonstrating the non-blocking nature of asynchronous programming in JavaScript.