Added HealthCheck (#188)

Checks home page.

src/Web/HealthChecks/HomePageHealthCheck.cs

@@ -0,0 +1,34 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.eShopWeb.Web.HealthChecks
+{
+    public class HomePageHealthCheck : IHealthCheck
+    {
+        private readonly IHttpContextAccessor _httpContextAccessor;
+
+        public HomePageHealthCheck(IHttpContextAccessor httpContextAccessor)
+        {
+            _httpContextAccessor = httpContextAccessor;
+        }
+
+        public async Task<HealthCheckResult> CheckHealthAsync(
+            HealthCheckContext context,
+            CancellationToken cancellationToken = default(CancellationToken))
+        {
+            string myUrl = _httpContextAccessor.HttpContext.Request.Host.ToString();
+            var client = new HttpClient();
+            var response = await client.GetAsync(myUrl);
+            var pageContents = await response.Content.ReadAsStringAsync();
+            if (pageContents.Contains(".NET Bot Black Sweatshirt"))
+            {
+                return HealthCheckResult.Healthy("The check indicates a healthy result.");
+            }
+
+            return HealthCheckResult.Unhealthy("The check indicates an unhealthy result.");
+        }
+    }
+}