XML declaration.

<?xml version="1.0" encoding="utf-8"?> 

This is the XML declaration.

version="1.0": Tells the XML parser to use version 1.0 rules.

encoding="utf-8": Says the text is encoded in UTF-8 (supports all languages and symbols).

Authentication and Authorization:

What is Authentication? 

 Authentication is the process of verifying who the user is. 

 - In ASP.NET MVC, authentication means checking if the user is logged in or not. 

 - It ensures that the user is genuine and valid. 

 - Common methods: Forms Authentication, Windows Authentication, OAuth, etc. 

 Example: When a user logs in using a username and password, the application verifies those credentials — this is authentication. 

 ---------------------------------------------------------------------------------------------------------------------------

 What is Authorization? 

 Authorization is the process of checking what the authenticated user is allowed to do. 

 - It decides what resources or actions the user can access. 

 - In MVC, we use [Authorize] attribute to restrict access to certain actions or controllers. 

 Example: After login, if only Admins can access the "Admin Panel", that check is done using authorization. 

 ----------------------------------------------------------------------------------------------------------------------------

 Simple Difference:

 | Feature                       | Authentication                        | Authorization 

-------------------------- --|--------------------------------- --|--------------------------------- 

 Meaning                       | Who are you?                         | What can you do?  

Comes First                   | Yes                                         | After authentication  

Purpose                          |Verify identity                        | Grant access       

ASP.NET MVC Tool     | FormsAuth, Identity, OAuth | [Authorize], Roles, Policies  

 --- Bonus Tip for Interview: > “Authentication checks identity, Authorization checks permissions. You must  authenticate first, then authorize.”

C# differences

#	Concept	Comparison	Example
1	Abstract Class vs Interface	Abstract class can have implementations; interface cannot.	abstract class A {} vs interface I {}
2	Ref vs Out	ref requires initialization, out does not.	void Method(ref int x) vs void Method(out int x)
3	Value Type vs Reference Type	Value types store data directly; reference types store memory addresses.	int x = 5; vs string s = "Hello";
4	== vs Equals()	== checks reference for objects, Equals() checks values.	"abc" == "abc" vs "abc".Equals("abc")
5	Sealed vs Static vs Abstract Class	sealed prevents inheritance, static prevents instantiation, abstract enforces method overriding.	sealed class A {}, static class B {}, abstract class C {}
6	Method Overloading vs Overriding	Overloading is same method with different parameters; Overriding modifies base method.	void Show(int x) vs override void Show()
7	Stack vs Queue	Stack: LIFO, Queue: FIFO.	Stack<int> stack = new Stack<int>();
8	Stack vs Heap	Stack stores value types; Heap stores reference types.	int x = 10; (Stack) vs new Person(); (Heap)
9	IEnumerable vs IQueryable	IEnumerable executes in-memory, IQueryable executes on the database server.	IEnumerable<T> (Linq in-memory) vs IQueryable<T> (Linq-to-SQL)
10	String vs StringBuilder	string is immutable, StringBuilder is mutable.	string s = "Hello"; vs StringBuilder sb = new();
11	Task vs Thread	Task is for async programming, Thread is for parallel execution.	Task.Run(() => {...}) vs new Thread(()=> {...}).Start();
12	ReadOnly vs Const vs Static	const is compile-time, readonly is runtime, static belongs to class.	readonly int a;, const int b = 10;, static int c;
13	Dispose vs Finalize	Dispose() is called explicitly; Finalize() is called by GC.	using(obj) {...} vs ~ClassName()
14	Early Binding vs Late Binding	Early binding is compile-time; Late binding is runtime.	var obj = new Class(); (early) vs dynamic obj = new Class(); (late)
15	XML vs JSON	XML uses tags, JSON uses key-value pairs.	<Person><Name>John</Name></Person> vs {"Name": "John"}
16	Static Constructor vs Instance Constructor	Static runs once per class; instance runs per object.	static Example() {} vs public Example() {}
17	DataSet vs DataReader	DataSet stores data in memory; DataReader reads forward-only.	DataSet ds = new DataSet(); vs SqlDataReader dr = cmd.ExecuteReader();
18	Hashtable vs Dictionary	Dictionary<T, T> is type-safe; Hashtable is not.	Dictionary<int, string> d = new();
19	Struct vs Class	struct is value type; class is reference type.	struct Point {} vs class Point {}
20	Interface vs Delegate	Interface defines behavior; Delegate is a method reference.	interface IRun {} vs delegate void MyDelegate();
21	IS vs AS Operator	is checks type compatibility; as performs safe casting.	if (obj is string) vs string s = obj as string;
22	Singleton vs Static Class	Singleton allows only one instance; Static class cannot be instantiated.	private static Singleton instance; vs static class MyClass {}
23	Lazy Loading vs Eager Loading	Lazy loads data when needed; Eager loads immediately.	Lazy<T> obj = new Lazy<T>();
24	Throw vs Throw ex	throw preserves stack trace, throw ex resets it.	throw; vs throw ex;
25	Partial Class vs Abstract Class	Partial splits a class, Abstract enforces overriding.	partial class MyClass {} vs abstract class MyClass {}
26	Deep Copy vs Shallow Copy	Deep Copy creates a new object, Shallow Copy copies reference.	Clone() for Deep, MemberwiseClone() for Shallow
27	Boxing vs Unboxing	Boxing converts value type to object, Unboxing retrieves value type from object.	object obj = 10; (Boxing) vs int x = (int)obj; (Unboxing)
28	Implicit vs Explicit Conversion	Implicit is automatic; Explicit requires casting.	int x = 10; double d = x; vs double d = 10.5; int x = (int)d;
29	Delegate vs Event	Delegate is a function pointer, Event is a restricted delegate.	delegate void MyDelegate(); vs event MyDelegate MyEvent;
30	Thread vs Process	Thread is lightweight; Process is heavyweight.	Thread t = new Thread(); vs Process p = new Process();

---

Process with an Id of '###' is not running" in Visual Studio || process with an id of '123' is not running

If an error occurs, right-click on the project and unload it. Then, right-click again and choose 'Edit'. After

 that, search for 'DevelopmentServerPort'. You will find the following lines

<DevelopmentServerPort>62343</DevelopmentServerPort>

<DevelopmentServerVPath>/</DevelopmentServerVPath>

<IISUrl>http://localhost:62878/</IISUrl>

Remove these lines, then reload the project. After that, run the project, and it will work.

VISA Thumb and Interview Process : This is what I experienced. I failed the interview today. Feeling very sad :(

 VISA Thumb and Interview Process:

Thumb Day:
On the DS-160 form, there is a "Completed On" date. This date must be within one year before the interview date.

For example, if you are attending the interview on January 2, 2024, the "Completed On" date should not be earlier than January 2, 2023. If it's incorrect, log in to the portal, update the date, and print the corrected form. Carry this updated printout with you. Otherwise, they might send you back, asking you to correct the date and return.

Today's required documents: Passport, DS-160 form, and appointment confirmation letter. These two printouts along with the original passport. You must attend with your thumb ready.

Interview Day:
Whatever information you entered in the DS-160 form will be asked during the interview. You must answer accurately and exactly as you filled in the form.

For example, if it’s about your date of birth, ensure you provide the exact details as mentioned in the form. Don’t provide more or less information than what’s in the form.

Today's required documents: Passport, DS-160 form, and appointment confirmation letter. These two printouts along with the original passport. If attending for B1, invitation letters are also needed. Additionally, original certificates, Xerox copies, salary-related payslips, and any other necessary documents would be better to carry.

I attended for B1. If someone else is inviting, they ask for a copy of their visa or passport. I heard them mentioning this there.

If you are going for this process, follow these steps. All the best!

Key SQL Server Instance Information Extracted Using the SERVERPROPERTY Function

The SQL query you've provided retrieves various properties related to the SQL Server instance using the SERVERPROPERTY function. Here's a breakdown of each property:

1. SERVERPROPERTY('ProductVersion') AS Version:

   • This returns the version number of the SQL Server instance (e.g., 15.0.2000.5 for SQL Server 2019). It indicates the specific release version.

2. SERVERPROPERTY('ProductLevel') AS ProductLevel:

   • This property returns the level of the product installed on SQL Server, such as:
     • RTM (Release to Manufacturing)
     • SP1, SP2, etc. (Service Pack versions)
     • CU (Cumulative Update)
     • It tells you whether your SQL Server is using a base version or has been updated to a service pack or cumulative update.

3. SERVERPROPERTY('Edition') AS Edition:

   • This indicates the edition of SQL Server installed, such as:
     • Express (a free, limited version of SQL Server)
     • Standard
     • Enterprise
     • Web
     • Developer
   • It helps in identifying the SQL Server edition that is running (which determines features and licensing).

4. SERVERPROPERTY('EngineEdition') AS EngineEdition:

   • This returns a numeric code representing the engine edition of SQL Server:
     • 1 = SQL Server (standalone)
     • 2 = SQL Azure (Cloud-based SQL)
     • 3 = SQL Server Express
     • 4 = SQL Server Web Edition
     • 5 = SQL Server Standard Edition
     • 6 = SQL Server Enterprise Edition
   • This is useful to know the underlying engine type.

5. SERVERPROPERTY('MachineName') AS MachineName:

   • This property returns the name of the machine (computer) where SQL Server is running. It is the same as the hostname of the server.

6. SERVERPROPERTY('IsClustered') AS IsClustered:

   • This returns a value indicating whether SQL Server is running in a clustered environment:
     • 0 = Not clustered
     • 1 = Clustered
   • This tells you if SQL Server is part of a high-availability cluster (typically used for fault tolerance).

Example of Output:

The result of this query would look something like this:

Version	ProductLevel	Edition	EngineEdition	MachineName	IsClustered
15.0.2000.5	SP1	Enterprise	6	MyServer	0

• Version: The SQL Server version.
• ProductLevel: The service pack or update level.
• Edition: The SQL Server edition (e.g., Enterprise).
• EngineEdition: The engine type (e.g., standalone SQL Server).
• MachineName: The machine hosting the SQL Server instance.
• IsClustered: Whether the SQL Server is clustered (0 = No).

This information can be useful for administrators to assess the configuration, version, and environment of the SQL Server instance.

How to send email from SQL Server || Using Database Mail to Send Emails in SQL Server || Configuring Email Notifications in SQL Server

 To send an email in a SQL Server trigger using SMTP2GO, you’ll need to create a stored procedure that sends emails through SMTP and call this procedure from within your trigger. Here’s a step-by-step guide to setting this up.

1. Enable Database Mail in SQL Server

First, ensure Database Mail is enabled on your SQL Server instance. Database Mail is required to send emails from SQL Server.

1. In SQL Server Management Studio (SSMS), go to Management > Database Mail.
2. Right-click and select Configure Database Mail to set up a mail profile if you haven't done so already.

2. Configure SMTP2GO Settings

Set up SMTP2GO as the SMTP server in SQL Server Database Mail:

• SMTP Server: mail.smtp2go.com
• SMTP Port: 2525 (or 587/465 for secure connections)
• Authentication: Use your SMTP2GO username and password for authentication.

In the Database Mail configuration, add these SMTP server details.

3. Create a Stored Procedure to Send Email

Now, create a stored procedure to send emails through Database Mail. This stored procedure will be called from your trigger.

CREATE PROCEDURE SendEmailUsingSMTP2GO

    @recipient NVARCHAR(255),

    @subject NVARCHAR(255),

    @body NVARCHAR(MAX)

AS

BEGIN

    EXEC msdb.dbo.sp_send_dbmail

        @profile_name = 'SMTP2GOProfile', -- Use the profile name you configured

        @recipients = @recipient,

        @subject = @subject,

        @body = @body,

        @body_format = 'HTML';

END

Replace 'SMTP2GOProfile' with the actual profile name created for Database Mail.

4. Create the Trigger to Call the Stored Procedure

Now, create a trigger that calls the SendEmailUsingSMTP2GO stored procedure to send an email when a specific action occurs on the table.

CREATE TRIGGER trgSendEmailOnInsert

ON YourTableName

AFTER INSERT

AS

BEGIN

    DECLARE @recipient NVARCHAR(255);

    DECLARE @subject NVARCHAR(255);

    DECLARE @body NVARCHAR(MAX);

    -- Set the recipient, subject, and body of the email

    SET @recipient = 'recipient@example.com';

    SET @subject = 'New Record Inserted';

    SET @body = 'A new record has been inserted into the table.';

    -- Call the stored procedure to send the email

    EXEC SendEmailUsingSMTP2GO

        @recipient = @recipient,

        @subject = @subject,

        @body = @body;

END

Replace YourTableName with the name of your table, and customize the @recipient, @subject, and @body variables as needed.

5. Test the Trigger

Insert a row into YourTableName to test if the trigger works and if the email is sent via SMTP2GO.

sql

INSERT INTO YourTableName (Column1, Column2) VALUES ('Value1', 'Value2');

If everything is set up correctly, you should receive an email at the specified recipient address.

Important Notes:

• Avoid Heavy Email Load in Triggers: Triggers are synchronous with the transaction, so email sending will block the transaction until it completes. If you expect high frequency, consider logging events and using a separate job to send emails.
• Error Handling: Consider adding error handling in your stored procedure or trigger to handle email sending failures gracefully.

Querystring Issue on C# with special characters

 If you're building a URL string dynamically in C#, you can use Uri.EscapeDataString to ensure proper encoding:

string searchTerm = "rock&roll";

string query = $"https://example.com/search?query={Uri.EscapeDataString(searchTerm)}";

This approach will automatically encode any special characters, including &, resulting in a safe and valid query string.

SQL Script to Terminate All Active Connections to a Specific Database || Kill Database connections

 -- Declare a cursor to iterate through the sessions

DECLARE @sessionId INT;

DECLARE kill_cursor CURSOR FOR

    SELECT session_id

    FROM sys.dm_exec_sessions

    WHERE database_id = DB_ID('DBName');

-- Open the cursor and loop through the sessions

OPEN kill_cursor;

FETCH NEXT FROM kill_cursor INTO @sessionId;

WHILE @@FETCH_STATUS = 0

BEGIN

    -- Print the session ID to be killed (for verification purposes)

    PRINT 'Killing session: ' + CAST(@sessionId AS VARCHAR(10));

    -- Kill the session

    EXEC('KILL ' + @sessionId);

    FETCH NEXT FROM kill_cursor INTO @sessionId;

END

-- Close and deallocate the cursor

CLOSE kill_cursor;

DEALLOCATE kill_cursor;

How do I create a unique constraint on a column in SQL Server?

 You can create a unique constraint using the ALTER TABLE command:

ALTER TABLE YourTableName ADD CONSTRAINT Unique_Constraint_Name UNIQUE (ColumnName);

This enforces a unique constraint on ColumnName.