MainForm.cs

using Furore.Fhir.ValidationDemo.Properties;
using Hl7.Fhir.Model;
using Hl7.Fhir.Serialization;
using Hl7.Fhir.Specification.Source;
using Hl7.Fhir.Validation;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Furore.Fhir.ValidationDemo
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();

            // Create a resource resolver that searches for the core resources in 'specification.zip', which comes with the .NET FHIR Specification NuGet package
            // We create a source that takes its contents from a ZIP file (in this case the default 'specification.zip'). We decorate that source by encapsulating
            // it in a CachedResolver, which speeds up access by caching conformance resources once we got them from the large files in the ZIP.
            CoreSource = new CachedResolver(ZipSource.CreateValidationSource());
        }

        internal IResourceResolver DirectorySource;
        internal IResourceResolver CoreSource;
        internal IResourceResolver CombinedSource;


        private void refreshProfileSource()
        {
            try
            {
                var profilePath = txtProfileDirectory.Text;

                if (!String.IsNullOrEmpty(profilePath) && Directory.Exists(profilePath))
                {
                    // We not only have a source for core data, we also read data from a user-specified directory. We also cache the contents of this source, like
                    // we did with the CoreSource above.
                    DirectorySource = new CachedResolver(new DirectorySource(profilePath, includeSubdirectories: true));

                    // Finally, we combine both sources, so we will find profiles both from the core zip as well as from the directory.
                    // By mentioning the directory source first, anything in the user directory will override what is in the core zip.
                    CombinedSource = new MultiResolver(DirectorySource, CoreSource);

                }
                else
                    CombinedSource = CoreSource;
            }
            catch(Exception e)
            {
                MessageBox.Show($"Composing the profile source failed: {e.Message}", "Profile source");
            }
        }

        private void txtProfileDirectory_TextChanged(object sender, EventArgs e)
        {
            refreshProfileSource();
        }

        private void btnReload_Click(object sender, EventArgs e)
        {
            refreshProfileSource();
        }

        private void MainForm_Load(object sender, EventArgs e)
        {
            refreshProfileSource();
        }

        private void btnOpenProfileDir_Click(object sender, EventArgs e)
        {
            if (!String.IsNullOrEmpty(txtProfileDirectory.Text))
                folderBrowserDialog.SelectedPath = txtProfileDirectory.Text;

            DialogResult result = folderBrowserDialog.ShowDialog();

            if (result == DialogResult.OK)
                txtProfileDirectory.Text = folderBrowserDialog.SelectedPath;
        }

        private void MainForm_FormClosed(object sender, FormClosedEventArgs e)
        {
            Settings.Default.Save();
        }

        private void btnValidate_Click(object sender, EventArgs e)
        {
            // The validator generates an OperationOutcome as output;
            OperationOutcome result = null;

            if (String.IsNullOrEmpty(txtInstanceXml.Text))
            {
                result = new OperationOutcome();
            }
            else
            {
                // Configure the validator based on the user's settings
                // This includes a reference to the resolver that we have constructed in previous methods
                // and which helps the validator to look for profiles
                ValidationSettings settings = ValidationSettings.Default;
                settings.EnableXsdValidation = chkXsdValidation.Checked;
                settings.Trace = chkShowTraceInfo.Checked;
                settings.ResourceResolver = this.CombinedSource;

                // This is a really cheap operation, so we can 
                var validator = new Validator(settings);
                var reader = SerializationUtil.XmlReaderFromXmlText(txtInstanceXml.Text);
                result = validator.Validate(reader);
            }

            if(result.Success)
            {
                txtOutcome.ForeColor = txtInstanceXml.ForeColor;
                txtOutcome.Text = result.ToString();
            }
            else
            {
                txtOutcome.ForeColor = Color.Red;
                txtOutcome.Text = result.ToString();
            }
        }
    }
}