Adding full DI navigation example for testing purposes.

- adding internal private field into FormBase class
- adding Extension methods into DependencyInjection namespace for use
- adding 2 NavigateTo extension methods for DI using ServiceProvider
- adding example project
- adding to readme as example

Examples/DependencyInjection/Database/BotDbContext.cs

@@ -0,0 +1,12 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace DependencyInjection.Database;
+
+public class BotDbContext : DbContext
+{
+    public BotDbContext(DbContextOptions options) : base(options)
+    {
+    }
+
+    public DbSet<User> Users { get; set; }
+}

Examples/DependencyInjection/Database/User.cs

@@ -0,0 +1,7 @@
+namespace DependencyInjection.Database;
+
+public class User
+{
+    public long Id { get; set; }
+    public string LastMessage { get; set; }
+}

Examples/DependencyInjection/Forms/ConfirmationForm.cs

@@ -0,0 +1,67 @@
+using DependencyInjection.Database;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TelegramBotBase.Base;
+using TelegramBotBase.Form;
+using TelegramBotBase.DependencyInjection;
+
+namespace DependencyInjection.Forms
+{
+    public class ConfirmationForm : FormBase
+    {
+        private readonly BotDbContext _dbContext;
+
+        public ConfirmationForm(BotDbContext dbContext)
+        {
+            _dbContext = dbContext;
+        }
+
+        public override async Task Load(MessageResult message)
+        {
+            var user = await _dbContext.Users.FindAsync(Device.DeviceId);
+
+            if (user == null)
+            {
+                await this.NavigateTo<StartForm>();
+                return;
+            }
+        }
+
+        public override async Task Action(MessageResult message)
+        {
+            await message.ConfirmAction("Go back");
+
+            switch (message.RawData)
+            {
+
+                case "back":
+
+                    await this.NavigateTo<StartForm>();
+
+                    break;
+
+            }
+
+
+        }
+
+        public override async Task Render(MessageResult message)
+        {
+            var user = await _dbContext.Users.FindAsync(Device.DeviceId);
+            if (user == null)
+                return;
+
+            var bf = new ButtonForm();
+            bf.AddButtonRow("Back", "back");
+
+            await Device.Send($"ConfirmationForm: Your last message was: {user.LastMessage}. Click \"Back\" to get back.", bf);
+        }
+
+
+
+
+    }
+}

Examples/DependencyInjection/StartForm.cs

@@ -0,0 +1,79 @@
+using DependencyInjection.Database;
+using DependencyInjection.Forms;
+using TelegramBotBase.Base;
+using TelegramBotBase.Form;
+using TelegramBotBase.DependencyInjection;
+
+namespace DependencyInjection;
+
+public class StartForm : FormBase
+{
+    private readonly BotDbContext _dbContext;
+
+    public StartForm(BotDbContext dbContext)
+    {
+        _dbContext = dbContext;
+    }
+
+    public override async Task Load(MessageResult message)
+    {
+        var user = await _dbContext.Users.FindAsync(Device.DeviceId);
+        if (user is null)
+        {
+            user = new User
+            {
+                Id = Device.DeviceId,
+                LastMessage = "<unknown>"
+            };
+
+            _dbContext.Users.Add(user);
+            await _dbContext.SaveChangesAsync();
+        }
+
+        if (message.IsAction)
+            return;
+
+
+        user.LastMessage = string.IsNullOrWhiteSpace(message.MessageText) ? "<unknown>" : message.MessageText;
+        await _dbContext.SaveChangesAsync();
+    }
+
+    public override async Task Action(MessageResult message)
+    {
+        await message.ConfirmAction("Ok");
+
+        switch(message.RawData)
+        {
+
+            case "open":
+
+                await this.NavigateTo(typeof(ConfirmationForm));
+
+                var new_form = await this.NavigateTo<ConfirmationForm>();
+
+                if (new_form == null)
+                {
+                    await Device.Send("Cant open ConfirmationForm");
+                }
+
+                break;
+
+        }
+
+
+    }
+
+    public override async Task Render(MessageResult message)
+    {
+        var user = await _dbContext.Users.FindAsync(Device.DeviceId);
+        if (user == null)
+            return;
+
+        var bf = new ButtonForm();
+
+        bf.AddButtonRow("Open confirmation", "open");
+
+        await Device.Send($"Your last message's text was: `{user.LastMessage}`", bf);
+    }
+
+}

README.md

@@ -1072,3 +1072,8 @@ Having already a web application and want to add a TelegramBot side-by-side with
 Want to use Inline- and ReplyMarkup at the same time ? Here is an example how you can do that:
 
 - [Examples/InlineAndReplyCombination](Examples/InlineAndReplyCombination)
+
+
+Alpha: Full Dependency Injection example within this framework.
+
+- [Examples/DependencyInjection](Examples/DependencyInjection)

TelegramBotBase/Base/FormBase.cs

@@ -32,6 +32,8 @@ public class FormBase : IDisposable
 
     public MessageClient Client { get; set; }
 
+    IServiceProvider _serviceProvider = null;
+
     /// <summary>
     ///     has this formular already been disposed ?
     /// </summary>

TelegramBotBase/DependencyInjection/Extensions.cs

@@ -0,0 +1,86 @@
+using Microsoft.Extensions.DependencyInjection;
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+using TelegramBotBase.Form;
+
+namespace TelegramBotBase.DependencyInjection
+{
+    public static class Extensions
+    {
+        internal static FieldInfo _ServiceProviderField = typeof(FormBase).GetField("_serviceProvider", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
+
+        /// <summary>
+        /// Use Dependency Injection to create new form and inject parameters. (Main variant)
+        /// </summary>
+        /// <typeparam name="NewForm"></typeparam>
+        /// <param name="args"></param>
+        /// <returns></returns>
+        public static async Task<NewForm> NavigateTo<NewForm>(this FormBase current_form, params object[] args)
+            where NewForm : FormBase
+        {
+            var _serviceProvider = current_form.GetServiceProvider();
+
+            var instance = ActivatorUtilities.CreateInstance(_serviceProvider, typeof(NewForm)) as NewForm;
+
+            if (instance == null)
+                return null; //throw new Exception("Could not instantiate new form via DI.");
+
+            instance.SetServiceProvider(_serviceProvider);
+
+            await current_form.NavigateTo(instance, args);
+
+            return instance;
+        }
+
+        /// <summary>
+        /// Use Dependency Injection to create new form and inject parameters. (Alternative variant)
+        /// </summary>
+        /// <param name="current_form"></param>
+        /// <param name="formBaseType"></param>
+        /// <param name="args"></param>
+        /// <returns></returns>
+        /// <exception cref="ArgumentException"></exception>
+        public static async Task<FormBase> NavigateTo(this FormBase current_form, Type formBaseType, params object[] args)
+        {
+            if (!typeof(FormBase).IsAssignableFrom(formBaseType))
+                throw new ArgumentException($"{nameof(formBaseType)} argument must be a {nameof(FormBase)} type");
+
+            var _serviceProvider = current_form.GetServiceProvider();
+
+            var instance = ActivatorUtilities.CreateInstance(_serviceProvider, formBaseType) as FormBase;
+
+            if (instance == null)
+                return null; //throw new Exception("Could not instantiate new form via DI.");
+
+            instance.SetServiceProvider(_serviceProvider);
+
+            await current_form.NavigateTo(instance, args);
+
+            return instance;
+        }
+
+        /// <summary>
+        /// Sets the internal service provider field.
+        /// </summary>
+        /// <param name="form"></param>
+        /// <param name="serviceProvider"></param>
+        public static void SetServiceProvider(this FormBase form, IServiceProvider serviceProvider)
+        {
+            _ServiceProviderField?.SetValue(form, serviceProvider);
+        }
+
+        /// <summary>
+        /// Gets the internal service provider field value.
+        /// </summary>
+        /// <param name="form"></param>
+        /// <returns></returns>
+        public static IServiceProvider GetServiceProvider(this FormBase form)
+        {
+            var sp = _ServiceProviderField?.GetValue(form) as IServiceProvider;
+            return sp;
+        }
+    }
+}

TelegramBotBase/Factories/ServiceProviderStartFormFactory.cs

@@ -1,5 +1,6 @@
 using System;
 using Microsoft.Extensions.DependencyInjection;
+using TelegramBotBase.DependencyInjection;
 using TelegramBotBase.Form;
 using TelegramBotBase.Interfaces;
 
@@ -16,14 +17,19 @@ public class ServiceProviderStartFormFactory : IStartFormFactory
         {
             throw new ArgumentException($"{nameof(startFormClass)} argument must be a {nameof(FormBase)} type");
         }
-
+        
         _startFormClass = startFormClass;
         _serviceProvider = serviceProvider;
     }
 
     public FormBase CreateForm()
     {
-        return (FormBase)ActivatorUtilities.CreateInstance(_serviceProvider, _startFormClass);
+        var fb = (FormBase)ActivatorUtilities.CreateInstance(_serviceProvider, _startFormClass);
+
+        //Sets an internal field for future ServiceProvider navigation
+        fb.SetServiceProvider(_serviceProvider);
+
+        return fb;
     }
 }