CODEWITHSUNDEEP
c#
TyneBridges
TyneBridges

Reputation: 57

What do the terms "context" and "_context" mean in .NET Core?

Can someone explain the meaning of these two terms to me: "_context" and "context"?

Coming from Basic, Pascal, and ASPX (VB) to C# and Razor pages, I constantly misunderstand the recent .NET terminology. I believe that the only essential context (that's referred to as such) in my database application is the context - that is, a class deriving from DbContext that handles database connections. However, this always seems to be handled in an oblique way. I see examples in tutorials like this:

public class CreateModel : DepartmentNamePageModel
    {
        private readonly ContosoUniversity.Data.SchoolContext _context;

        public CreateModel(ContosoUniversity.Data.SchoolContext context)
        {
            _context = context;
        }

If the first line within the function is creating a new instance of the context, why (since I already have this defined and able to list items from my tables) do I get a syntax error

The name '_context' does not exist in the current context"

when I adapt it into my own code? I've added all the references from the top of the example pages. Why do we need a model within a model here, and what does the last statement do?

I've looked in this tutorial for clarification and done searches, but everything I read seems to assume we're already fluent in this way of using objects. I particularly need to grasp this because the only working example of a dropdown I can find uses these cross-references, and what I expected to be a simple task has tied me in knots.

Upvotes: 2

Views: 2748

Answers (1)

Francisco Goldenstein
Francisco Goldenstein

Reputation: 13767

The constructor gets an instance of ContosoUniversity.Data.SchoolContext (injected, for example) and then you set it to a field called _context. Both variables are referencing the same object. If you didn't want to have two different names, you would use "this" like this:

public class CreateModel : DepartmentNamePageModel
{
    private readonly ContosoUniversity.Data.SchoolContext context;

    public CreateModel(ContosoUniversity.Data.SchoolContext context)
    {
        this.context = context; // "this" refers to the field defined in this class and not the parameter of the constructor
    }

Upvotes: 4

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