What is the best practice to get the context of subsite?

Question

I have created a provider hosted app with adfs. In this app I have the SP clientContext of the site collection. I have a form in this app. When the user submits the form, there will be created a subsite.

// Set the clientcontext for the SPHost
Microsoft.SharePoint.Client.ClientContext clientContext = SharePointContextProvider.Current.GetSharePointContext(HttpContext.Current).CreateUserClientContextForSPHost();

// Create new subsite
Web newWeb = clientContext.Web.CreateWeb(new OfficeDevPnP.Core.Entities.SiteEntity()
            {
                Title = "subsite1",
                Url = "subsite1",
                Description = "subsite1",
                Template = "BLANKINTERNET#0",
                Lcid = (uint)1043
            }, true, true);

After creating "subsite1" I would like to create a second subsite under "subsite1". But I need first to get the client context of "subsite1".

How can I get the client context of an spweb? Maybe by url?

UPDATE

I am trying now to open the subsite1 and create a subsite2 under subsite1. I got the exception:

Ensure that this object or its parent (such as an SPWeb or SPSite) is being properly disposed. This object is holding on to a separate native heap.

And this is the stacktrace:

at Microsoft.SharePoint.Client.ClientRequest.ProcessResponseStream(Stream responseStream)
   at Microsoft.SharePoint.Client.ClientRequest.ProcessResponse()
   at Microsoft.SharePoint.Client.ClientContextExtensions.ExecuteQueryImplementation(ClientRuntimeContext clientContext, Int32 retryCount, Int32 delay)
   at Microsoft.SharePoint.Client.WebExtensions.CreateWeb(Web parentWeb, String title, String leafUrl, String description, String template, Int32 language, Boolean inheritPermissions, Boolean inheritNavigation)
   at Microsoft.SharePoint.Client.WebExtensions.CreateWeb(Web parentWeb, SiteEntity subsite, Boolean inheritPermissions, Boolean inheritNavigation)
   at CompanyName.SharePoint.ProvisioningWeb.Controllers.HomeController.Index() in E:\VSO\CompanyName\Main\CompanyName\CompanyName.SharePoint.ProvisioningWeb\Controllers\HomeController.cs:line 38
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f()

Here is the code:

[SharePointContextFilter]
        public ActionResult Index()
        {
            User spUser = null;

            var spContext = SharePointContextProvider.Current.GetSharePointContext(HttpContext);

            using (var clientContext = spContext.CreateUserClientContextForSPHost())
            {
                if (clientContext != null)
                {
                    spUser = clientContext.Web.CurrentUser;

                    clientContext.Load(spUser, user => user.Title);

                    clientContext.ExecuteQuery();

                    ViewBag.UserName = spUser.Title;

                    /////////////////////

                    var subweb1 = clientContext.Site.OpenWeb("sub1");
                    clientContext.Load(subweb1);
                    clientContext.ExecuteQueryRetry();

                    // Create new subsite
                    Web sub2 = subweb1.CreateWeb(new OfficeDevPnP.Core.Entities.SiteEntity()
                    {
                        Title = "sub2",
                        Url = "sub2",
                        Description = "sub2", // todo, deze beschrijving wordt niet opgeslagen in de site
                        Template = "BLANKINTERNET#0",
                        Lcid = (uint)1043
                    }, true, true);

                    // Load the url property (office dev extension method)
                    sub2.EnsureProperty(w => w.Url);

                    string sub2Title = sub2.Title;
                }
            }

            return View();
        }

Answer 1

The easiest way is to construct web object using OpenWeb method like this:

var subweb = clientContext.Site.OpenWeb("subsite1");
clientContext.Load(subweb);
clientContext.ExecuteQueryRetry();  

Later you can you use subweb in order to create a new site.