Query String in ASP.NET Core 3 Web API

Create ASP.NET Core 3 Web API Project

On the Visual Studio, create new ASP.NET Core Web Application project

Input Project Name and select Project Location

Select Empty Template and click Create button to Finish

Structure of New Project

Add Configurations

Open Startup.cs file and add new configurations as below:

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace LearnASPNETCore3WebAPIWithRealApps
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

Create Controller

Create new folder named Controllers. In this folder, create new controller named DemoController.cs as below:

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;

namespace DemoASPNETCoreWebAPI.Controllers
{
    [Route("api/demo")]
    public class DemoController : Controller
    {

        [Produces("text/plain")]
        [HttpGet("demo1")]
        public async Task<IActionResult> Demo1()
        {
            try
            {
                string id1 = HttpContext.Request.Query["id1"].ToString();
                int id2 = int.Parse(HttpContext.Request.Query["id2"].ToString());
                return Ok("Id1: " + id1 + ", Id2: " + id2);
            }
            catch
            {
                return BadRequest();
            }
        }

        [Produces("text/plain")]
        [HttpGet("demo2")]
        public async Task<IActionResult> Demo2([FromQuery(Name = "id1")] string id1, [FromQuery(Name = "id2")] int id2)
        {
            try
            {
                return Ok("Id1: " + id1 + ", Id2: " + id2);
            }
            catch
            {
                return BadRequest();
            }
        }

    }
}

Structure of ASP.NET Core 3 Web API Project

Testing Web API

Access restful web services use the following url: http://localhost:64967/api/demo/demo1?id1=p01&id2=456

Output

Id1: p01, Id2: 123

Access restful web services use the following url: http://localhost:64967/api/demo/demo2?id1=p02&id2=789

Output

Id1: p02, Id2: 789

Consume Web API from Console Application

Create Console App (.NET Framework) Project in Visual Studio.

Create DemoRestClientModel

DemoRestClientModel class contain methods call Web API

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

namespace LearnASPNETCore3WebAPIWithRealApps_Client
{
    public class DemoRestClientModel
    {
        private string BASE_URL = "http://localhost:64967/api/demo/";

        public Task<HttpResponseMessage> Demo1(string id1, int id2)
        {
            try
            {
                HttpClient client = new HttpClient();
                client.BaseAddress = new Uri(BASE_URL);
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("text/plain"));
                return client.GetAsync("demo1?id1=" + id1 + "&id2=" + id2);
            }
            catch
            {
                return null;
            }
        }

        public Task<HttpResponseMessage> Demo2(string id1, int id2)
        {
            try
            {
                HttpClient client = new HttpClient();
                client.BaseAddress = new Uri(BASE_URL);
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("text/plain"));
                return client.GetAsync("demo2?id1=" + id1 + "&id2=" + id2);
            }
            catch
            {
                return null;
            }
        }
    }
}

Run Console Application

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

namespace LearnASPNETCore3WebAPIWithRealApps_Client
{
    class Program
    {
        static void Main(string[] args)
        {
            DemoRestClientModel demoRestClientModel = new DemoRestClientModel();

            Console.WriteLine("Test Demo1 Web Method");

            HttpResponseMessage httpResponseMessage = demoRestClientModel.Demo1("p01", 456).Result;

            HttpStatusCode httpStatusCode = httpResponseMessage.StatusCode;
            Console.WriteLine("Status Code: " + httpStatusCode);

            bool isSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
            Console.WriteLine("IsSuccessStatusCode: " + isSuccessStatusCode);

            string result = httpResponseMessage.Content.ReadAsStringAsync().Result;
            Console.WriteLine("Result: " + result);

            Console.WriteLine("\nTest Demo2 Web Method");
            HttpResponseMessage httpResponseMessage2 = demoRestClientModel.Demo2("p02", 789).Result;

            HttpStatusCode httpStatusCode2 = httpResponseMessage2.StatusCode;
            Console.WriteLine("Status Code: " + httpStatusCode2);

            bool isSuccessStatusCode2 = httpResponseMessage2.IsSuccessStatusCode;
            Console.WriteLine("IsSuccessStatusCode: " + isSuccessStatusCode2);

            string result2 = httpResponseMessage2.Content.ReadAsStringAsync().Result;
            Console.WriteLine("Result: " + result2);

            Console.ReadLine();
        }
    }
}

Output

Test Demo1 Web Method
Status Code: OK
IsSuccessStatusCode: True
Result: Id: p01, Id2: 456

Test Demo2 Web Method
Status Code: OK
IsSuccessStatusCode: True
Result: Id1: p02, Id2: 789