c# - Why is the Up() method abstract and the Down() method virtual in the DbMigration class -

-

if @ signature of abstract class dbmigration in system.data.entity.migrations namespace:

public virtual void down(); public abstract void up();

you'll see down() marked virtual , up marked abstract. difference between virtual , abstract abstract function can have functionality in it.

what kind of functionality can up() function have default , why isn't case th down() function.

you need override up() while overriding down() optional. makes sense database migration instructions.

see what difference between abstract function , virtual function?.


Comments

Post a Comment

Popular posts from this blog

node.js - How to mock a third-party api calls in the backend -

-
i'm testing application mocha , supertest, test like var request = require('supertest'), app = require('./bootstrap.js'); describe('...', function() { it('...', function() { request(app) .get('/some/url') // ... }); }); the bootstrap.js real application before listen ports all works perfect have add calls third-party api , testing slow so when do, test example takes 5 seconds request(app) .get('/my/endpoint/that/makes/call/others') // ... how can make fake calls during test real when running application? you can use nock purpose.
Read more

node.js - Why do I get "SOCKS connection failed. Connection not allowed by ruleset" for some .onion sites? -

-
i'm experimenting node , socks5-https-client . reason, tor hidden service ( .onion ) sites return connection error. for example, connecting duckduckgo ( 3g2upl4pq6kufc4m.onion ) works , returns html. however, connecting pirate bay ( uj3wazyk5u4hnvtk.onion ) or torch ( xmh57jrzrnw6insl.onion ) returns... error: socks connection failed. connection not allowed ruleset. what error mean? how can avoid it? here's code reproduce it: var shttps = require('socks5-https-client'); shttps.get({ hostname: '3g2upl4pq6kufc4m.onion', path: '', sockshost: '127.0.0.1', socksport: 9150, rejectunauthorized: false }, function(res) { res.setencoding('utf8'); res.on('readable', function() { console.log(res.read()); // log response console. }); }); the error seems caused 0x02 value in field 2 of server response. in summary the servers you're failing access don't support ...
Read more

Entity Framework - The property cannot be configured as a navigation property -

-
i'm defining 2 entities following, strange behavior occurring: [table("clienttypes", schema="dbo")] public clienttype { [key] public int id { get; set; } public string name { get; set; } } [table("clients", schema="dbo")] public client { [key] public long id { get; set; } [foreignkey("clienttypeid")] public int clienttypeid { get; set; } public virtual clienttype clienttype { get; set; } } i'm getting clienttypeid property filled value, clienttype object filled nothing. can me this? thank all! the foreignkey attribute have on wrong property. the annotation may placed on foreign key property , specify associated navigation property name, or placed on navigation property , specify associated foreign key name. - source [foreignkey("clienttypeid")] should decorate public virtual clienttype clienttype instead, or change [foreignkey("clienttype...
Read more