unable to drop and create database in sql server

1. Right-click on the database and select "Delete" (or left-click it and press the 'del' key).
2. When the 'Delete Object' dialog appears, make sure to checked "Close existing connections" (see below, it's unchecked by default).
3. Press "OK".

We usually get this error If You've opened any query window with connection to this database, so make sure you close all your opened query windows connected to db which you're trying to drop.

Don't use the database which you're trying to drop. use master to drop any user database that is a good practice.

Make sure No other process is attach to the database you're trying to drop.

EXEC sp_who2
--Run kill spid for each process that is using the database to be dropped.
kill <<processid>> -- Kill 57

Use EXEC sp_who2 and check the DBName column, your database name should not appear in the list, if it appears kill the process using kill <<processid>> then try to drop.

Try this code.

use master
GO

IF EXISTS (SELECT name FROM master.dbo.sysdatabases WHERE name = N'test')
DROP DATABASE [test]
GO

CREATE DATABASE [test]
GO

use [test]
GO