If you want the list of databases currently being used / active connections

 SELECT 

    DB_NAME(database_id) AS DatabaseName,

    COUNT(*) AS ActiveConnections

FROM sys.dm_exec_sessions

WHERE database_id > 0

GROUP BY database_id

ORDER BY ActiveConnections DESC;

If you want BOTH list of customer DBs + active connections

SELECT 

    d.name AS DatabaseName,

    ISNULL(c.ActiveConnections, 0) AS ActiveConnections

FROM sys.databases d

LEFT JOIN (

    SELECT database_id, COUNT(*) AS ActiveConnections

    FROM sys.dm_exec_sessions

    GROUP BY database_id

) c ON d.database_id = c.database_id

WHERE d.name LIKE 'C%';

Could not copy "obj\Debug\etc" to "obj\Debug\etc". Exceeded retry count of 10. Failed.

 1. Stop the Running Application

• Make sure your app (yourapp(ur application name)) is not running.
• Open Task Manager (Ctrl+Shift+Esc) → go to Details tab.
• Find yourapp(ur application name)) → End Task.
• Rebuild your project.

2. Clean and Rebuild

• In Visual Studio:
  • Go to Build → Clean Solution
  • Then Build → Rebuild Solution
• This clears the obj and bin folders and rebuilds everything fresh.

3. Check for Debugger/Antivirus Locks

Sometimes, even if the EXE isn’t running:

• Antivirus software may be scanning or locking the file — temporarily disable real-time protection or add your project folder to exceptions.

• Visual Studio Debugger might not have released the file — close the solution and reopen it.

4. Manually Delete Locked Files

If the above doesn’t work:

1. Close Visual Studio.
2. Open File Explorer → navigate to your project folder.
3. Delete the folders:

   bin\Debug
   obj\Debug
   

4. Reopen Visual Studio → Rebuild.

If Windows says “file is in use,” use a tool like Process Explorer:

• Download from Microsoft Sysinternals.

• Search for (yourapp(ur application name)) → right-click → Kill Process.

5. Disable Parallel Builds (Optional)

If your solution has multiple projects:

• Go to Tools → Options → Projects and Solutions → Build and Run
• Set “maximum number of parallel project builds” = 1

This avoids concurrent file access issues.

6. Check Post-Build Events

If you have a post-build script that copies or runs the EXE, ensure it’s not launching the app before the next build.

How to download (clone) a Git repository into a specific folder ?

If you want to download (clone) a Git repository into a specific folder, you can do it very easily using the git clone command with a folder path at the end. 

Option 1 – Clone directly into a specific folder Command format: git clone 

Example: git clone https://github.com/username/Notes.git D:\Projects\NotesApp 

This will: Download the Git repository into the folder D:\Projects\NotesApp If the folder doesn’t exist, Git will create it automatically. 

Option 2 – Clone in current folder with custom name. If you’re in a directory (e.g. D:\Projects) and you want to clone the repo into a subfolder with a custom name, do this: 

cd D:\Projects (Enter)

git clone https://github.com/username/Notes.git 

MyNotes It will create a folder called MyNotes inside D:\Projects and put the repo code there.

Get Location

Your Location

Getting location...

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.