CODEWITHSUNDEEP
sql-serverdatabaseasp.net-mvc-3entity-frameworkvisual-studio-2012
jpo
jpo

Reputation: 4059

Query specific table in C# Visual Studio database

I am new to Visual Studio MVC3 and trying to connect to a database. I have my connection string in the web.config file:

add name="con" connectionString="Data Source=190.190.200.100,1433;Network Library=DBMSSOCN;Initial Catalog=myDataBase; User ID=myUsername;Password=myPassword;" providerName="System.Data.SqlClient"

However, the server has multiple tables. How/where will I specify which table to use when querying the database?

EDIT:
For example, I am looking at this example. How does the application differentiate between the tables to display data? When you call return View(db.Students.ToList()) as in the example in the link, how does the application know to look in the student table and not in the enrollment table?

Upvotes: 1

Views: 1978

Answers (1)

Christian Specht
Christian Specht

Reputation: 36441

How does the application differentiate between the tables to display data? When you call return View(db.Students.ToList()) as in the example in the link, how does the application know to look in the student table and not in the enrollment table?

The db.Students part comes from Entity Framework.

Read the "Creating the Database Context" section in the link that you posted.
You will find the following code there:

using System;
using System.Collections.Generic;
using System.Data.Entity;
using ContosoUniversity.Models;
using System.Data.Entity.ModelConfiguration.Conventions;

namespace ContosoUniversity.Models
{
    public class SchoolContext : DbContext
    {
        public DbSet<Student> Students { get; set; }
        public DbSet<Enrollment> Enrollments { get; set; }
        public DbSet<Course> Courses { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
        }
    }
}

This sets up the database context, which is basically Entity Framework's "setup", from where it knows which C# class it has to map to database tables.

So db.Students (from your question) is actually a DbSet<Student>.

Entity Framework's default convention looks like this: it tries to map a class to a table with the same name.
Usually, it would map the Student class to a table named Students (pluralized), but you can change/override these conventions...which they also did in this example, in this line:

modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

This is also explained in the tutorial, directly under the above code.
Quote from the tutorial:

This code creates a DbSet property for each entity set. In Entity Framework terminology, an entity set typically corresponds to a database table, and an entity corresponds to a row in the table.

The statement in the OnModelCreating method prevents table names from being pluralized. If you didn't do this, the generated tables would be named Students, Courses, and Enrollments. Instead, the table names will be Student, Course, and Enrollment. Developers disagree about whether table names should be pluralized or not. This tutorial uses the singular form, but the important point is that you can select whichever form you prefer by including or omitting this line of code.

Upvotes: 2

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