I want to show Components in a tabs , so first of all create few components. In this project we have three components, First View Component public class AllViewComponent : ViewComponent { private readonly UserManager<ApplicationUser> _userManager; public AllViewComponent(UserManager<ApplicationUser> userManager) { _userManager = userManager; } public async Task<IViewComponentResult> InvokeAsync() { List<StudentViewModel> allUsers = new List<StudentViewModel>(); var items = await _userManager.Users.ToListAsync(); foreach (var item in items) { allUsers.Add(new StudentViewModel {Id=item.Id, EnrollmentNo = item.EnrollmentNo, FatherName = item.FatherName, Name = item.Name, Age = item.Age, Birthdate = item.Birthdate, Address = item.Address, Gender = item.Gender, Email = item.Email }); }
In Computer Programming, C# Data types are divided into two broad categories such as Value types and Reference type. In Value types, some inbuilt types such as int, float, double, structs, enum etc. These all are non-nullable types, it means these types don't hold null value. In other hand Reference types such as string, Interface, Class, delegates, arrays etc. can hold null value.
By default value types are non nullable. To make them nullable use, programmer have to use ?- int a=0 a is non nullable, so a cannot be set to null, a=null will generate compiler error
- int ?b=0 b is nullable int, so b=null is legal
Operator Need
If programmer want to assign null value to non-nullable data types then there are some operators explained with an example.
Lets take an simple example
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
{
class Program
{
static void Main(string[] args)
{
int a;
int? b = 100;
a = b ?? 0;
System.Console.WriteLine(a);
Console.ReadKey();
int? b = 100;
a = b ?? 0;
System.Console.WriteLine(a);
Console.ReadKey();
}
}
}
}
}
Output show that if b hold some value like 100 then Null coalescing operator assign value to variable (a). If b hold null value then Null coalescing operator assign default value, which is zero to variable a.
Replace the declaration of variable b with the following line:
int? b = Null;
This will outputs zero (default value).
Comments
Post a Comment