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The semaphore class lets you set a limit on the number of threads that have access to a critical section. The class is used to control access to a pool of resources. System.Threading.Semaphore is the namespace for Semaphore because it has all the methods and properties required to implement Semaphore.For using a semaphore in C#, you just need to instantiate an instance of a Semaphore object. It has minimum of two arguments −Reference−MSDNSr.No.Constructor & Description1Semaphore(Int32, Int32)Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries.2Semaphore(Int32, Int32, String) −Initializes a ... Read More
For a case-insensitive query, use regex in MongoDB. Let us create a collection with documents −> db.demo314.insertOne({"Name":"Chris brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50d742f8647eb59e562056") } > db.demo314.insertOne({"Name":"David Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50d743f8647eb59e562057") } > db.demo314.insertOne({"Name":"CHRIS BROWN"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50d744f8647eb59e562058") } > db.demo314.insertOne({"Name":"DAVID MILLER"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50d747f8647eb59e562059") } > db.demo314.insertOne({"Name":"chris brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50d749f8647eb59e56205a") }Display all documents from a collection with the help of find() method −> db.demo314.find();This will produce the following output −{ "_id" ... Read More
JShell is an interactive tool for learning the Java language and prototyping Java code. It is a REPL (Read-Evaluate-Print-Loop) that evaluates declarations, statements, and expressions once entered and immediately prints the results in JShell. This tool runs from the command-line prompt.The modifiers like public, protected, private, static, and final have not allowed on top-level declarations and can be ignored with a warning. The keywords like synchronized, native, abstract, and default top-level methods have not allowed and can be errors.In the below code snippets, we have created both final and static variables. It prints out a warning message to the user that "Modifier 'final' or 'static' not permitted ... Read More
Let us create a collection with documents −> db.demo313.insertOne({"_id":100, "details":[{"Name":"Chris", "Age":24}]}); { "acknowledged" : true, "insertedId" : 100 } > db.demo313.insertOne({"_id":101, "details":[{"Name":"David", "Age":22}]}); { "acknowledged" : true, "insertedId" : 101 } > db.demo313.insertOne({"_id":102, "details":[{"Name":"Mike", "Age":25}]}); { "acknowledged" : true, "insertedId" : 102 }Display all documents from a collection with the help of find() method −> db.demo313.find();This will produce the following output −{ "_id" : 100, "details" : [ { "Name" : "Chris", "Age" : 24 } ] } { "_id" : 101, "details" : [ { "Name" : "David", "Age" : 22 } ] } { "_id" : 102, "details" ... Read More
To update partial number of documents, set multi to true. Let us create a collection with documents −> db.demo312.insertOne({"FirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce16f8647eb59e56204a") } > db.demo312.insertOne({"FirstName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce19f8647eb59e56204b") } > db.demo312.insertOne({"FirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce1cf8647eb59e56204c") } > db.demo312.insertOne({"FirstName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce20f8647eb59e56204d") } > db.demo312.insertOne({"FirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50ce22f8647eb59e56204e") }Display all documents from a collection with the help of find() method −> db.demo312.find();This will produce the following output −{ "_id" : ObjectId("5e50ce16f8647eb59e56204a"), "FirstName" ... Read More
For faster queries, create an index. To get the count, use count(). Let us create a collection with documents −> db.demo311.ensureIndex({"Name":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo311.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd01f8647eb59e562044") } > db.demo311.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd05f8647eb59e562045") } > db.demo311.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd06f8647eb59e562046") } > db.demo311.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd0af8647eb59e562047") } > db.demo311.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cd0df8647eb59e562048") } > db.demo311.insertOne({"Name":"Chris"}); { ... Read More
To push document into an array, use $push along with update(). Let us create a collection with documents −>db.demo310.insertOne({"Name":"Chris", "details":[{"Id":101, "Subject":"MySQL"}, {"Id":102, "Subject":"MongoDB"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e50cabdf8647eb59e562043") }Display all documents from a collection with the help of find() method −> db.demo310.find();This will produce the following output −{ "_id" : ObjectId("5e50cabdf8647eb59e562043"), "Name" : "Chris", "details" : [ { "Id" : 101, "Subject" : "MySQL" }, { "Id" : 102, "Subject" : "MongoDB" } ] }Following is the query to push document −> db.demo310.update({ _id:ObjectId("5e50cabdf8647eb59e562043")}, ...{ $push: {"details": { ... "Id" ... Read More
To remove, use remove() in MongoDB. Let us create a collection with documents −> db.demo309.insertOne({ "details":[ { "Name":"Chris" }, { "Name":"David" }, { "Name":"Adam" } ] } ); { "acknowledged" : true, "insertedId" : ObjectId("5e4eb71af8647eb59e562040") } > db.demo309.insertOne({ "details":[ { "Name":"David" }, { "Name":"Mike" }, { "Name":"Bob" } ] } ); { "acknowledged" : true, "insertedId" : ObjectId("5e4eb7cbf8647eb59e562041") }Display all documents from a collection with the help of find() method −> db.demo309.find();This will produce the following output −{ "_id" : ObjectId("5e4eb71af8647eb59e562040"), "details" : [ { "Name" : "Chris" }, { "Name" : "David" }, { "Name" ... Read More
To retried a subset of fields, use dot notation in find(). Let us create a collection with documents −> db.demo307.insertOne({ ... "CleintId":101, ... "ClientDetails":{"ClientFirstName":"Chris", "Age":34}, ... "ClientCountryName":"US" ...} ...); { "acknowledged" : true, "insertedId" : ObjectId("5e4eab88f8647eb59e56203c") } > db.demo307.insertOne({ ... "CleintId":102, ... "ClientDetails":{"ClientFirstName":"David", "Age":31}, ... "ClientCountryName":"UK" ...} ...); { "acknowledged" : true, "insertedId" : ObjectId("5e4eab97f8647eb59e56203d") }Display all documents from a collection with the help of find() method −> db.demo307.find();This will produce the following output −{ "_id" : ObjectId("5e4eab88f8647eb59e56203c"), "CleintId" : 101, "ClientDetails" : { "ClientFirstName" : "Chris", "Age" : 34 ... Read More
To fetch documents, use find() in MongoDB. With that, to format the resultant documents, use pretty().Let us create a collection with documents −> db.demo306.insertOne({"Name":"Robert", "Age":21}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7c6f8647eb59e562038") } > db.demo306.insertOne({"Name":"David", "Age":23}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7cdf8647eb59e562039") } > db.demo306.insertOne({"Name":"Mike", "Age":25}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7d4f8647eb59e56203a") } > db.demo306.insertOne({"Name":"Carol", "Age":26}); { "acknowledged" : true, "insertedId" : ObjectId("5e4ea7dcf8647eb59e56203b") }Display all documents from a collection with the help of find() method −> db.demo306.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e4ea7c6f8647eb59e562038"), "Name" : ... Read More