Query from one to many relation database to datatable-CodePudding

I am just starting with SQL and trying to get my first example working. I have two tables with a one-to-many relation:

public class Customer
{
    public Guid Id { get; set; }
    public string CompanyName { get; set; }
    public string Address { get; set; }
    [JsonIgnore]
    public virtual ICollection<Project> Projects { get; set; }
}

public class Project
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string ProjectType { get; set; }
    public Guid CustomerId { get; set; }
    public Customer Customer { get; set; }
}

Then I am executing following command through API ProjectsController:

[HttpGet]
public async Task<IActionResult> Get()
{
    System.Collections.Generic.List<Project> projects = 
         await _context.Projects.Include(d => d.Customer).ToListAsync();
    return Ok(projects);
}

I am getting my

private IEnumerable<Project> ProjectsList { get; set; } = new List<Project>();

on the razor page, with

this.ProjectsList = await this.HttpClient.GetFromJsonAsync<IEnumerable<Project>>("api/Projects");

I have checked data structure of ProjectsList with debugger and it looks fine.

However: the Razor page table (two columns "Project name" and "Customer name"):

<Table DataSource="ProjectsList" TItem="Project">
  <Column TData="string"
          Title="Name"
          @bind-Field="context.Name"
          SorterCompare="@((a,b)=> string.Compare(a,b))"
          SortDirections="new[] { SortDirection.Descending }"
          Filterable />
    <Column TData="string"
    @bind-Field="context.Customer.CompanyName"
    SorterCompare="@((a,b)=> string.Compare(a,b))"
    SortDirections="new[] { SortDirection.Descending }"
    Filterable />
</Table>

I get an exception of object not set to instance of object. I guess this is because of context.Customer.CompanyName where Customer is not initialized?

First of all I have a question should I redo my Project model and add there additional column of type string CompanyName or there is some other way to get data displayed on razor page?

In case if... I should add additional column into Project.cs how to query data using linq in there?

CodePudding user response：

First off, try the following, and if you get an error, post its text here:

public Customer Customer { get; set; } = new Customer {};