MVC

• Introduction to formatting response data in ASP.NET Core MVC 1
• MVC 6 for ‘Building a Web App with ASP.NET Core, MVC 6, EF Core, and Angular’
• Razor wiki page

Model Binding

The MVC pipeline processes each incoming request through a sequence of stages before executing the action method. Model binding is the stage that populates action method parameters from the request.

flowchart LR
    REQ([Request]) --> CI[Controller\nInitialization]
    CI --> AMS[Action Method\nSelection]
    AMS --> MB[Model\nBinding]
    MB --> AME[Action Method\nExecution]
    AME --> RES([Response])

    FD([Form Data]) --> MB
    RD([Route Data]) --> MB
    QS([Query String]) --> MB
    FILE([File Data]) --> MB

Model binding reads values from Form Data, Route Data, Query String, and File Data and populates the action method parameters automatically.

public IActionResult NewClient(Client newClient)
{
    return View();
}

Form Data Binding

When an HTTP POST is submitted, the Form Value Provider reads each field from the request body and the Model Binder maps those values onto a new instance of the target class.

flowchart LR
    subgraph req["HttpRequest (Simplified)"]
        FD["Form Data\n──────────────\nFirstName: Joe\nLastName: Smith\nCompanyName: Cypher\nPhone: 555-555-1234\nContactDate: 10/10/2016\nClientType: Individual"]
    end

    subgraph target["Client Class"]
        CC["public class Client {\n  public string FirstName{}\n  public string LastName{}\n  public string CompanyName{}\n  public string Phone{}\n}"]
    end

    FD -->|field values| FVP[Form Value\nProvider]
    FVP <-->|binding| MB[Model\nBinder]
    MB -->|reads properties| target
    MB -->|creates| NCI["New Client\nInstance"]

    NCI --> ACTION["public IActionResult NewClient(Client newClient)"]

The Model Binder reflects over the Client class properties and assigns each matching form field value, producing a fully-populated object passed directly into the controller action.

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