Use cookies in ASP.NET Core

  Cookie is often used to save a piece of data related to the user and saved on the client computer. In most browsers, each cookie will exist in the form of a small file, except for Firefox, which saves all cookies in a file. Among them, the cookie is expressed in the form of key-value, which can be used to read, delete, write and other operations

  ASP.NET Core uses the cookie mechanism to maintain the session state. In every request from the client, the server will put the sessionid in the cookie and send it to the client for user tracking.

Read cookie

• To read Cookie ASP.NET Core can be used in the Request.Cookiesproperty, cookie read from the Request object

string cookie = Request.Cookies["Key"];

• If you want to set a cookie expiration time, you can use Cookies.Appendoverloaded methods, as shown in the following code:

CookieOptions option = new CookieOptions(); 
option.Expires = DateTime.Now.AddMilliseconds(10); 
Response.Cookies.Append(key, value, option); 

  As you can see from the code above, CookieOptions can be used to configure some additional parameters during the cookie generation process

parameter	Description
Domain	Used to specify the domain level associated with the cookie
Expiration time	Used to specify the expiration time of the cookie
Path	Used to specify the path of the cookie
Security policy	Used to specify whether the cookie can be accessed through Https
HttpOnly	Used to specify whether the cookie is available on the server side

Write cookie

• To write cookie, you can use Cookies.Appendthe method

Response.Cookies.Append(somekey, somevalue);

Delete cookie

• To delete the cookie, you can use Cookies.Deletethe method

Response.Cookies.Delete(somekey);

Use HttpContext

  How to use the ASP.NET Core cookie, cookie must have in order to get Requestthe object, in order to obtain the Request object must have HttpContext, in order to get HttpContextnecessary to take advantage of IHttpContextAccessorthe interface

 public interface IHttpContextAccessor
{
    
    
	HttpContext HttpContext {
    
     get; set; }
}

• ASP.NET Core on a built-in implements the interface HttpContextAccessorclass

public class HttpContextAccessor : IHttpContextAccessor
{
    
    
	public HttpContextAccessor();

	public HttpContext HttpContext {
    
     get; set; }
}

  Some people may ask, why not just use the parent class here Controller 's Requestand HttpContextthis is because this approach is a strong dependence, then everyone shows how to get dependency injection by the way HttpContext, this is more flexible.

  In order to achieve dependency injection, necessary IHttpContextAccessorand HttpContextAccessorinjected into ServiceCollection, the following cases will be a single injection mode

public void ConfigureServices(IServiceCollection services)
{
    
    
	services.AddSingleton<IHttpContextAccessor,
	HttpContextAccessor>();
	// 逻辑代码
}

  Can then be obtained by injection-dependent manner IHttpContextAccessorinstance of an interface, and then sequentially acquiring HttpContextobjects, the following code fragment shows how to access the Controller IHttpContextAccessorexample

public class HomeController : Controller
{
    
    
    private readonly IHttpContextAccessor _httpContextAccessor;
    public HomeController(IHttpContextAccessor httpContextAccessor)
    {
    
    
        this._httpContextAccessor = httpContextAccessor;
    }   
  // 逻辑代码
}

Write cookie in Controller

• Write the data to the cookie in the Controller by the following method

public IActionResult Write(string key, string value, bool isPersistent)
{
    
    
	CookieOptions options = new CookieOptions();
	if (isPersistent)
		options.Expires = DateTime.Now.AddDays(1);
	else
		options.Expires = DateTime.Now.AddSeconds(10);
	_httpContextAccessor.HttpContext.Response.Cookies.Append(key, value, options);
	return View("WriteCookie");
}

Read cookie in Controller

• Once the cookie is successfully written, you can use the following method to read the cookie

public IActionResult Read(string key)
{
    
    
	ViewBag.Data = _httpContextAccessor.HttpContext.Request.Cookies[key];
	return View("ReadCookie");
}

• You can use the browser's developer tools whether to view Cookie successfully written and read to

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