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Using non-standard UI's with mvvmcross? (databindings for things like gtksharp)

I'm looking into getting started with C# app development. I have experience in web-based technologies but am just starting up with desktop/MVVM.
I've been watching and reading up on various mvvmcross tutorials, and I'm really looking forward to working on an application using the framework, but I just have a quick question which might have more to do with databindings than mvvmcross itself:
If I build my application.core through the mvvmcross library, would it be relatively easy to reuse that core library to develop UI's for non-mvvmcross targets?
I understand that mvvmcross simplifies a LOT of the display logic, so by doing this I would have to write up code to connect with other guis using their methods, but I'm wondering if anybody can comment on
a) Whether it would be possible
and
b) If it would be possible without a lot of workarounds/hacking around my mvvmcross core implementation.
My use-case is that I plan on using mvvmcross to develop for either WPF or WinStore first, then, if there is demand, add a Mac UI. But eventually, if the demand is there, I want to be able to also port my application to Linux (probably through gtksharp,because it sounds like that's furthest ahead in development right now). Would my application.gtk project be able to easily call/work with the classes, methods, and functions that are defined in the mvvmcross core application, or would that logic have to be re-written to handle data in a way that's more suitable to gtksharp?
Thanks.

Sorry for the super-late reply, but I don't really think this is too feasible, at least as stated. The main problem, as I see it, is that MvvmCross would still likely have to be a dependency for most of your core library(ies). You could certainly have a core library with that as a dependency and just not really use it, but that seems like a waste and kind of goes against the question as asked.
Without it as a dependency, you lose quite a lot of stuff, really all the stuff that makes it such a nice framework. What you'd really want to do is just implement INotifyPropertyChanged and work off of that. Some other, simpler libraries you might be able to use include the Bind library from Praeclarum (https://github.com/praeclarum/Bind), Fody.PropertyChanged (https://github.com/Fody/PropertyChanged), Json.NET, and SqLite.NET to achieve a basic but powerful core library that can then be added to with an MvvmCross-based library, but I don't know if there'd even be any reason to do that. Another helpful link would be: http://arteksoftware.com/end-to-end-mvvm-with-xamarin/.

Normally when developing the core with MvvmCross (but actually any Mvvm pattern using style of development) the Core should not depend on any UI logic, and thus should be re-usable on any platform. However currently there is no platform support for gtk in MvvmCross.
I'm not really familiar with gtk, but I suppose it's possible to build the binding layer for linux in a similar way as was done for Android and iOS.
So in theory you should be able to re-use the Core libraries on Linux as well using Mono, given such binding layer for Linux would be developed for MvvmCross. I'd be interested to see anyone start poking around if this is actually possible.

What are the first steps in C#/.NET development?

Okay, I'm biting the bullet and deciding to get into the whole Microsoft/C#/.NET culture and I'm going to do this by putting together a simple (hah!) application.
It will basically be an application in which I want to store images and associate with them other optional things.
It must be able to import images from the filesystem (and hopefully camera/scanner) then allow the user to add text, audio and other information.
I plan to store the images and auxillary information into a database. What the application will do with said data isn't important (yet).
Keep in mind I know absolutely nothing about C# or .NET although, as an old codger, I know a great deal about many other things and will regale/bore you with stories and anecdotes until you quietly slip away :-)
What are the first steps to take in developing such an application? I've already set out UI layouts and likely process flows although it may be that the development environment dictates changes.
Development environment is currently XP SP3 + VS2008 (though I can upgrade if absolutely necessary).
What should I be looking at as the first step? Are there any gotchas I should be looking out for?

Have you decided for win forms or WPF? I've been doing win forms for the past 4 years and WPF was a great discovery for me, with the flexibility it affords. It might be fitted for your application and the different types of content you'll want to add and give you a flexibility that win forms can't give.
As for actually developing, I think loading images from the disk would be the first step, showing them in the UI and getting user input for them - you would get to work with the different objects and see how the framework handles things.
A tutorial about the field validation I mentioned in my comment is here - haven't done it, but something similar. You can also see the xaml code paired with the C# code there.
After looking for the differences between win forms and WPF I found that there are a few win forms controls that are missing from WPF. More on that on MSDN (compariosn chart) and a post from March with a more detailed chart.
It's also worth mentioning that you can include win forms controls in WPF applications and vice versa, but there are some limitations.

Just a couple of pointers, it would be easy to overwhelm you as you are just starting with this tech stack. First step, use SQLServer 2008 Express, it has better ability to deal with image data (images can be saved directly to the filesystem, but they are still in a table).
Apart from that, you can design your screen with the GUI, and then hook the bits up one by one to your retreived data. Create a new Windows Forms app, or a WPF one, and start from there (i'm assuming that you know about the toolbox window and just dragging components on to the designer and setting their properties in the Properties window).

If you're looking win forms you're going to have drag-and-drop UI pretty easily.
If you want to use a database than you're probably going to find MS-SQL the easiest to cooperate with. Look up LINQ-2-SQL, it lets you access your database through an object layer by simply dragging your tables onto a pane.
Fun things to use: extension methods, partial classes, LINQ (query any collection with inline lambdas) and even class/method attributes.

My $0,02:
a) Get to know the platform a bit, types, collections, events/delegates(/lambdas), etc etc
b) Dive into WPF
c) Learn about database connectivity (LINQ2SQL or NHibernate (or ....)
d) Learn about the MVVM pattern to get to deliver solid wpf applications, doing so forces you to dive deeper into the workings of WPF (routed commands, tunneling/bubbleing etc)
e) Learn more about patterns to get a more solid grasp of OO (this: http://www.amazon.com/Design-Patterns-Explained-Perspective-Object-Oriented/dp/0321247140/ref=sr_1_1?ie=UTF8&s=books&qid=1276066663&sr=8-1 is an absolute pearl for that)
f) etc

If you aren't too desperate to get your hands dirty straight away I'd suggest this book: CLR via C#.
It is written for those with programming experience on platforms other than .Net and provides a clear and comprehensive explanation of C# and how it runs on the .NET CLR.
By reading this initially you might avoid writing some of the poorly constructed applications that many of us wrote before properly understanding the technology.

Buy a book on C# & .NET FW fundamentals!
Read! :-)

Read good books about .NET for example CLR via C#.
Read this:
Hidden Features of C#? https://stackoverflow.com/questions/380819/common-programming-mistakes-for-net-developers-to-avoid

Best Architecture for Reporting Application in ASP.net ( with dynamic Sources)

the Requirement in simple words goes like this.
Its a charting Application ( kinda Dashboard) with multiple views (Charts , PDF and Excel)
DataSources could be primarily from Oracle but there are other data sources like Excel,flat Files....etc.
Charting library would be Component art (I would like to try the new asp.net charting but as its already being used in other apps they would like to continue)
As I told you, We have a already have an application which is like basic 3 layered with some DTOs and mostly DataTables;where I feel any data model is tightly coupled with Views, they would like to continue with the same :)
I would like to propose a new architecture for this and I need your honest comments.
I think
It should be designed using traditional MVC pattern, as there is one model and different Views(chart,excel,pdf)
A Solid Service layer(Enterprise Lib) with 1) Security(Provider model) 2)Data source Abstraction (flat files , oracle , excel) 3) Caching ( each report would have its own refresh time and the data/view can be cached accordingly 4)Error logging 5)Health monitoring
3) using WCF services to expose the views or DTOs
4) Complete AJAX and partial rendering
5) develop a solid wcfservice which would take the datamodel name and view(chart,excel,pdf then returns the view accordingly.
Please guide me, I want to build a loosely coupled and configurable architecture which can be reused.

Honest answer: It sounds like you are either over-engineering this, or you are irresponsibly re-inventing the wheel.
I want to build a loosely coupled and
configurable architecture which can be
reused.
That's a lovely goal, but is it a requirement of this project? I'm guessing it's not a fundamental requirement, at most a nice-to-have. It seems that the business needs a dashboard with some exportable charts and reports, and you're proposing to build a platform. That's classic over-engineering.
If you really need a reusable platform, it will take considerable effort and skills to build an intuitive, robust, secure, testable, configurable, maintainable reporting platform with sophisticated and trainable authoring tools.
And even if you build a perfect platform, you'll have a custom system that nobody else knows. If you use an established BI/reporting platform, you can hire people who already know the technology or point people at reams of already existent training materials.
In other words, it's going to be difficult and more expensive to build, which is bad, but also difficult and more expensive for the organization to use for years to come, which is worse. I routinely choose build over buy, but reporting is a known problem that has been solved well enough by commercial platforms.
So, sure, that architecture sounds reasonable. And without knowing more about the requirements, it's impossible to judge: maybe you really do need to build this from scratch, but from your description "charting Application ( kinda Dashboard)", building a reporting platform sounds unnecessary, though perhaps quite fun.

I recommend the following book:
Microsoft® .NET: Architecting Applications for the Enterprise by Dino Esposito; Andrea Saltarello.
They are discussing architecture in a pragmatic way (Yes there are code examples). Many of the things you have mentioned will be described in the book. You will probably not get all the answers but it will inspire you. (They have made a book about Ajax/ASP.NET arch too but I have not read that one)
You want to use a lot of new cool technology, that’s cool. But most important is why do you want to use it, what business value will it add? Ask yourself what do you want to with your product in the future? To be able to figure out today and tomorrows requirement will be the best thing to help you build “loosely coupled and configurable architecture” it will help you more then any of the techs you have choosen.

My motto is always buy before reuse before build. From the requirements, you could be better off buying a COTS BI solution. They have very robust feature sets and provide the capability to do things like charting, pdf/excel export out-of-the-box. There are tons of vendors, Microsoft has their own BI suite. Oracle has theirs, etc...

Consider using a flexible reporting Engine like List&Label which is also used by SAP. Maybe using some kind of ETL Tool + DataWarehouse might be an option for you too (not enough information on your requirements though). Maybe there is some kind of common pattern in the datasource you have not observed so far.
List&Label is pretty powerful, however i have never used it in a web app. Abstracting your DataSources with simple AnnonymousTypes, then translating them to DataSets and doing the rest with List&Label has served me well for a number of small tasks. See modelshredder for a tool that can help you with it.

I think you can make a loosely coupled architecture that is flexible. It is actually pretty simple. Create a table that contains all of your reporting SQL and bind the results to a gridview. The individual SQL is pulled from the tables via a drop-down menu of categories and reports. You can add additional tables with sub-selects to drill down and rebind upon row selection. Use the parameters from the Oracle Data Access to include dates, filters, etc. from any controls that may be present on the front-end.
Once the data is dynamically bound and displayed, give the users the option to email the grid contents, export to PDF, Excel, etc.
I've implemented this # 2 client sites and it saves them a ton of money of buying licenses from Crystal, MS, etc. and is much more flexible.

Developing a new application with .NET?

I have to develop a basic "line of business" application with the usual functionality like orders, stock control, sales, reports, etc.
I will use WPF to develop this application to run on Windows but I want to develop it "open" so I can do a Windows Forms application using the same structure (maybe to run over Mono) or even a Silverlight module. Can someone that did something like that (and survived) give me a sugestion on a guideline or something like that where I can find good practices? I'm a Delphi developer with some intermediate knowledge on C# but there are so many "amazing" libraries, frameworks and patterns that I'm a little lost on what would be good for that project.
Something like: Use EF (maybe wait for ef4?) or nHibernate, or ADO.NET, and expose your data using WCF, or webservices, or forget Mono because of the flexibility loss, etc. Can someone give me a tip on how you would do it? If someone has a bad experience in this type of project, it would be nice to hear from you as well. There is a lot of learning in the wrong decisions too :)

Mono doesn't implement WPF, it's not even on the roadmap. I'm not sure about Entity Framework...
You could probably do it in Silverlight (which has an open source implementation), but it's not ideal for creating desktop (although it is possible since Silverlight 3)

Where do I start?
First, from your description, you're in over your head.
Second, you're trying to pick a technology stack when everything is new to you.
In the best situation, I'd recommend a good training class in a few of the technologies you mentioned so you get a better understanding of them. I'd also recommend a mentor, someone who's done this before.
Reality though, may not allow for training or a mentor. In that case I'd recommend writing several real-life throw away programs. Take one piece of business functionality and try to write it in a few of the technologies you mentioned. If one feels better, and gives you what you want DECISION MADE! Don't stop with the first one that seems to work, try some more.
You should also listen to some good podcasts. I recommend Dot Net Rocks for a good grasp of the technology. The earlier podcasts for this site were also a very good source for some design discussions StackOverflow podcast
Best of luck.

I had to do something very similar recently in WPF. I have an ASP.NET background, but I have never worked with WPF (or WinForms for that matter), and it had me stumped for a while, but the longer I have been working on it (about 3 weeks now), the easier it has gotten. I really just searched Stack Overflow and Google for code snippets similar to what I was doing, and worked through them and changed them as needed. My company bought a book that helped me out as well (It was WPF Unleashed published by Sams), and it was pretty good. I do wish you luck on your first WPF app.

If you separate the business model and business logic from the user interface,
using MVC (Model View Controller) or MVVM (Model View View-Model) or a simular design pattern,
then you can have multiple user interfaces connected to the same business model + business logic and even connect the same user interface to other business models + business logic.

Thank you all for your suport... Brad, I'm already following your advices, doing some test cases to see what looks good... my problem is that altough I can develop an application in WPF and have a intermediate understanding in using the wpf databindings, generics, linq, anonymous objects, all the cool stuff, I always hear about this and that as the solution for all the worlds problems (like mvvm, or parallel programming, or functional languages, etc) and makes me feel "wrong" in my decisions and a bad developer if I do not use any of this nice technologies. I know the concepts but do not dominate it, and seems a lot of things to learn, sadly I do not have that much time.
Thomas, exactly because mono do not support WPF i want to make the application as isolated as i can, so I can do a simple winform layer to manipulate the data.
darthnosaj, thank you, I'm doing that too, searching internet and found much information (and this nice site full of hellpful people :) )
And Danny, thats what i think i need... will take a look on some sample applications using mvvm and see if that works for me. For what i heard is almost a crime not to use in that case in wich I want that kind of isolation.
Again, thanks all :)

I would suggest you keep your application N-Tier. Make all the entities, data adapter, and business logic separated from the actual desktop application. This way you can use WPF on the Windows platform and use Mono/GTK# on the Linux/Mac platforms.
You will only need to write duplicate code to support the actual GUI application functionality, while your code from the separate entity/data access/business logic library (e.g. DLL/class library) can be used in both your WPF and Mono/GTK# projects. Just add the DLL as a reference to the WPF and Mono/GTK# projects.
There is a good video from Channel 9 on building N-Tier applications
There is also MSDN documentation and guidelines on building N-Tier applications

Implementing a fully-functional prototype for a web-based application

I am building a prototype for a web-based application and was considering building the front-end in HTML, which can then be reused later for the actual application. I had done a Flash-based prototype earlier, which embedded the .swf into a C# executable. Flash made for rapid turnaround time while the Windows application provided unlimited access to fancy API's for DB access and sound.
I want to consider something similar for this one too. Does this approach make sense? I am particularly concerned about the way the HTML would communicate with the container app. From what I understand out of preliminary research, it would be only through JavaScript, which might quickly get unwieldy. This is especially so because unlike the Flash-based prototype which implemented a lot of its functionality in the .swf, the HTML UI will depend entirely upon the shell to maintain state. Also, I don't need anything more than access to a database. So a desktop application might be overkill.
Another alternative that comes to mind is to build the prototype using PHP and deploy it with a portable server stack such as Server2Go or XAMPP. But I've never done something like this before. Anybody here shed some light on drawbacks of this approach?
The key requirement is rapid iterations of the UI, reusable front-end code and simplified deployment without any installations or configuration.

Some of the best programming advice I've seen came from Code Complete, and was along the lines of, "evolutionary prototypes are fine things, and throwaway prototypes are fine things, but you run into trouble when you try to make one from the other." That is, know which type of prototype you're developing, and respect it. If you're developing a throwaway prototype, don't permit yourself to use any of it, however tempting it may be, in the production system. And if you're developing an evolutionary prototype - one intended to become the production system - don't compromise quality in any way.
It sounds like you're trying to get both, the rapid development of a throwaway and the reusability of an evolutionary prototype - and you can't. Make up your mind, and stand by it. You can't have your cake and eat it, too.

I think you off to the wrong start, here. Why would you want your prototype to be fully functional? A prototype is intended to be throw-away and to help flesh out requirements and UI. If you need full functionality, why not just skip to the final product? If prototyping is really something you want to do, I suggest looking into a specialized prototyping tool.

Are you prototyping the user interface for a customer? If you are, consider something less unwieldy like paper prototypes or presentation software (like PowerPoint) until you get the UI nailed down. If you can establish the UI and are clear about the customer's requirements, you can then develop the application in whatever the actual platform is going to be with a clear model in mind.
In my current project, I prototyped the UI in PowerPoint first. In a subsequent iteration, I used static web pages and some jQuery plugins to simulate actual user interaction. That proved to be very effective in demonstrating the interface, and I didn't have to build the application first.

I would join in on folks suggesting paper prototyping as the "idea", but not necessarily the implementation. The biggest point here is that tools such as HTML or Flash let you get "bogged down" in the details - what does this color look like? What's the text on this thing? Lots of time can pass by that way. Instead, what you should be focusing on is user flows.
One tool that keeps the spirit of paper prototyping without all the "paper" drawbacks is Balsamiq: http://www.balsamiq.com/demos/mockups/Mockups.html. It was covered by Jeff and Joel in one of the Stack Overflow podcasts; I've been using it for my own projects for a while. It's freeware, and it does its job magnificently.

If you know C# then another option you can look at is Silverlight. You can then leverage your knowledge of C# and/or JavaScript and interact with a rich object model.
Would that do what you are looking for? The installation would be minimal on the part of the client - download and install the Silverlight plugin

If prototyping is something you truly wish to accomplish here, paper and pencil will be your best friends. You can draw out as many iterations as necessary. While none of this is ultimately useful later on once you begin coding, it is as quick and rapid is it goes.
As mentioned previously, there are many prototyping tools which have a bit of a learning curve, but an alternative to consider would be using a framework such as CakePHP or Ruby on Rails which make for fast application logic and leave customizing the front end being the primary hard work left. And plus, you're left with a mostly functional application when you're done with your prototyping which can be tweaked as needed.
In either scenario, you're paying with your time either upfront (in the case with learning a new framework), of over time in payments (with the case of prototyping on paper or coding by hand).