Here’s an example of how to Group by multiple columns using LINQ in C#.

Create an Asp.NET Core MVC or Web API Project

Assuming you have Visual Studio 2019 or Visual Studio 2022 installed, follow these steps to create a new ASP.NET Core Project

• Open the visual studio (IDE).
• Click on the “Create new project” option.
• Choose “ASP.NET Core Web Application” from the list of available templates.
• Click the Next button.
• The configure a new project, specify the name and location of your project.
• Click the “Next” button.
• Then select .Net Core as the runtime and choose the version from the dropdown list at the top.
• Make sure to uncheck the checkboxes for “Enable Docker Support” and “Configure for HTTPS” since we won’t be using authentication.
• Click the “Create” button

Consider an example Employee class with properties like FirstName, LastName, City, and State. We’ll group employees based on their City and State.

Create a Model

namespace WEB_API_without_EF.Models
{
    public class Employees
    {
        public int ID { get; set; }
        public string Company { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Email { get; set; }
        public string JobTitle { get; set; }
        public string Address { get; set;}

        public string City { get; set; }

        public string state { get; set; }

    }
}

Create a Controller

namespace WEB_API_without_EF.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class EmployeeController : ControllerBase
    {

        [HttpGet("GetgroupBy")]
        public IActionResult GetgroupBy()
        {
            List<Employees> employees = new List<Employees>
            {
                new Employees{FirstName="Anna", LastName="Bedecs", Company="Company A", City="Seattle",state="WA"},
                new Employees{FirstName="Antonio", LastName="Gratacos Solsona", Company="Company B", City="Boston",state="MA"},
                new Employees{FirstName="Thomas" ,LastName="Axen", Company="Company C", City="Seattle",state="WA"},
                new Employees{FirstName="Christina", LastName="Lee", Company="Company D", City="New York",state="NY"},
                new Employees{FirstName="Martin" ,LastName="O’Donnell", Company="Company E", City="Minneapolis",state="MN"},
                new Employees{FirstName="Francisco", LastName="Pérez-Olaeta", Company="Company F", City="Milwaukee",state="WI"},

            };

            var groupemployee = from emp in employees
                                group emp by new { emp.City, emp.state } into empgroup
                                select new
                                {
                                   Name =$"City : {empgroup.Key.City} State : {empgroup.Key.state}",
                                   employees= empgroup.ToList(),
                                };
            
      

            return Ok(groupemployee);

        }
}
}

Output:

See More :

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