<\/p>\n
About Web Host and Web Host Extension<\/strong><\/h5>\nFirst, what is the WebHost? This is the class responsible for handling application startup\u00a0 and lifetime management. This includes logging, dependency injection and configuration.<\/p>\n
You can take a look by opening the Startup.cs file<\/p>\n
Now we would like to extend this class, so that when the application starts up, the migration and seeders are run as well.<\/p>\n
<\/p>\n
Create the Web Host Extension<\/strong><\/h5>\nWe would place this inside a folder called extensions. So follow the steps below:<\/p>\n
Step 1<\/strong> – Create a folder called Extensions<\/p>\nStep 2<\/strong> – Inside this folder, create a class called WebHostExtensions. The content of this class is given below<\/p>\npublic<\/span> static<\/span> class<\/span> WebHostExtensions<\/span>\r\n{\r\n public<\/span> static<\/span> IHost Initialize<\/span>( this<\/span> IHost host)\r\n {\r\n using(var<\/span> scope = host.Services.CreateScope())\r\n {\r\n var<\/span> services = scope.ServiceProvider;\r\n var<\/span> context = services.GetRequiredService<HospitalContext>();\r\n context.Database.Migrate();\r\n }\r\n return<\/span> host;\r\n }\r\n}\r\n<\/pre>\nSee the video for explanation.<\/p>\n
Step 3<\/strong> – Open your Program.cs file and adjust your main method like so<\/p>\npublic<\/span> static<\/span> void<\/span> Main<\/span>(string<\/span>[] args)\r\n{\r\n var<\/span> host = CreateHostBuilder(args).Build();\r\n host.Initialize().Run();\r\n}\r\n<\/pre>\n <\/p>\n
Step 4<\/strong> – Now you can run the program everything runs fine as well. Now delete the database and remove the connection. Run the program again, you will notice that the database is created again and all the tables are created as well.<\/p>\nCreate the Seeders<\/strong><\/h5>\nSo basically, we use seeders to add some initial data to the database. So for each of the table, we would have class. All of them would be in a folder. Let’s follow the steps;<\/p>\n
Step 1<\/strong> – Create a folder called Seeders.<\/p>\nStep 2<\/strong> – Inside this folder, create a file called CountrySeeder (we start with this). The content of the CountrySeeder class is given below. So just copy and paste it.<\/p>\npublic<\/span> class<\/span> CountrySeeder<\/span>\r\n{\r\n private<\/span> readonly<\/span> HospitalContext _context;\r\n public<\/span> CountrySeeder<\/span>(HospitalContext context)\r\n {\r\n _context = context;\r\n }\r\n\r\n public<\/span> void<\/span> Seed<\/span>()\r\n {\r\n AddNewCountry(new<\/span> Country { CountryId = 1<\/span>, Name = \"India\"<\/span>, Capital = \"New Delhi\"<\/span> });\r\n AddNewCountry(new<\/span> Country { CountryId = 2<\/span>, Name = \"Nigeria\"<\/span>, Capital = \"Abuja\"<\/span> });\r\n AddNewCountry(new<\/span> Country { CountryId = 3<\/span>, Name = \"Hungary\"<\/span>, Capital = \"Budapest\"<\/span> });\r\n _context.SaveChanges();\r\n }\r\n\r\n \/\/ since we run this seeder when the app starts<\/span>\r\n \/\/ we avoid adding duplicates, so check first, then add<\/span>\r\n private<\/span> void<\/span> AddNewCountry<\/span>(Country country)\r\n {\r\n var<\/span> existingType = _context.Countries.FirstOrDefault(c => c.CountryId == country.CountryId);\r\n if<\/span> (existingType == null<\/span>)\r\n {\r\n _context.Countries.Add(country);\r\n }\r\n }\r\n}\r\n<\/pre>\nWatch the video for an explanation of the codes.<\/p>\n
Step 5<\/strong> – Open the WebhostExtensions class and add the code below. Add it immediately under the context.Database.Migrate() line.<\/p>\n\/\/Lets not seed the database by calling the seeders<\/span>\r\nnew<\/span> CountrySeeder<\/span>(context).Seed();\r\n<\/pre>\n <\/p>\n
We would place this inside a folder called extensions. So follow the steps below:<\/p>\n
Step 1<\/strong> – Create a folder called Extensions<\/p>\n Step 2<\/strong> – Inside this folder, create a class called WebHostExtensions. The content of this class is given below<\/p>\n See the video for explanation.<\/p>\n Step 3<\/strong> – Open your Program.cs file and adjust your main method like so<\/p>\n <\/p>\n Step 4<\/strong> – Now you can run the program everything runs fine as well. Now delete the database and remove the connection. Run the program again, you will notice that the database is created again and all the tables are created as well.<\/p>\n So basically, we use seeders to add some initial data to the database. So for each of the table, we would have class. All of them would be in a folder. Let’s follow the steps;<\/p>\n Step 1<\/strong> – Create a folder called Seeders.<\/p>\n Step 2<\/strong> – Inside this folder, create a file called CountrySeeder (we start with this). The content of the CountrySeeder class is given below. So just copy and paste it.<\/p>\n Watch the video for an explanation of the codes.<\/p>\n Step 5<\/strong> – Open the WebhostExtensions class and add the code below. Add it immediately under the context.Database.Migrate() line.<\/p>\n <\/p>\npublic<\/span> static<\/span> class<\/span> WebHostExtensions<\/span>\r\n{\r\n public<\/span> static<\/span> IHost Initialize<\/span>( this<\/span> IHost host)\r\n {\r\n using(var<\/span> scope = host.Services.CreateScope())\r\n {\r\n var<\/span> services = scope.ServiceProvider;\r\n var<\/span> context = services.GetRequiredService<HospitalContext>();\r\n context.Database.Migrate();\r\n }\r\n return<\/span> host;\r\n }\r\n}\r\n<\/pre>\npublic<\/span> static<\/span> void<\/span> Main<\/span>(string<\/span>[] args)\r\n{\r\n var<\/span> host = CreateHostBuilder(args).Build();\r\n host.Initialize().Run();\r\n}\r\n<\/pre>\nCreate the Seeders<\/strong><\/h5>\n
public<\/span> class<\/span> CountrySeeder<\/span>\r\n{\r\n private<\/span> readonly<\/span> HospitalContext _context;\r\n public<\/span> CountrySeeder<\/span>(HospitalContext context)\r\n {\r\n _context = context;\r\n }\r\n\r\n public<\/span> void<\/span> Seed<\/span>()\r\n {\r\n AddNewCountry(new<\/span> Country { CountryId = 1<\/span>, Name = \"India\"<\/span>, Capital = \"New Delhi\"<\/span> });\r\n AddNewCountry(new<\/span> Country { CountryId = 2<\/span>, Name = \"Nigeria\"<\/span>, Capital = \"Abuja\"<\/span> });\r\n AddNewCountry(new<\/span> Country { CountryId = 3<\/span>, Name = \"Hungary\"<\/span>, Capital = \"Budapest\"<\/span> });\r\n _context.SaveChanges();\r\n }\r\n\r\n \/\/ since we run this seeder when the app starts<\/span>\r\n \/\/ we avoid adding duplicates, so check first, then add<\/span>\r\n private<\/span> void<\/span> AddNewCountry<\/span>(Country country)\r\n {\r\n var<\/span> existingType = _context.Countries.FirstOrDefault(c => c.CountryId == country.CountryId);\r\n if<\/span> (existingType == null<\/span>)\r\n {\r\n _context.Countries.Add(country);\r\n }\r\n }\r\n}\r\n<\/pre>\n\/\/Lets not seed the database by calling the seeders<\/span>\r\nnew<\/span> CountrySeeder<\/span>(context).Seed();\r\n<\/pre>\n
![\"Records](\"https:\/\/www.kindsonthegenius.com\/wp-content\/uploads\/2021\/06\/Records-Seeded-to-the-Countries-Table-300x156.jpg\")
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