I have got knowledge about Expression Blend which is used to create graphical user interfaces (Wpf) in a similar way to Visual Studio. Is it free for download? In any case, can anything produced by Blend be implemented with identical code (markup) in Visual Studio?
Could somebody recommend me a detailed and comprehensive "tutorial" of how to build Wpf in VS and how to develop effective use of its controls?
Expression Blend is not free. But there's a 30day Trial version available.
I use both Blend and VS but as I am more a SW-Developer and not a designer 95% of my WPF work is done with VS. Everything that you can accomplish with the Blend editor can also be done with the VS Editor.
In VS a lot of stuff like Storyboards have to be coded manually and are quite tricky, there-as Blend gives you tools for this task which makes it a lot easier.
Have a look at this introductory video: http://expression.microsoft.com/en-us/cc136522
You'll find lots of helpful webcasts on the Expression Website: http://expression.microsoft.com/en-us/cc197141
Expression Blend is not free.
Blend is not a must, for being able to design WPF UI.
It can be compared to Photoshop-like applications + it works on XAML without losing DataBinding information. But its "duty" is only design. As a developer I found myself much more comfortable with XAML manipulation than with Blend. But, it's a matter of test and a matter of abilities you have.
For examples just google. This one was just the first in the list I found:
Wpf Tutorial
Everything that Expression Blend can do you can do in Visual Studio, but you'll have to code some of the extra effects directly in the XAML by hand. Essentially Expression Blend gives you automated XAML generation of the fancier graphics, that Visual Studio doesn't.
You'll also find that it will guide you towards MVVM pattern WPF/Silverlight.
I couldn't recommend any single resource myself, but if you search for MVVM pattern WPF on the internet there's plenty of examples out there. Admittedly many are Silverlight, but the basics still stand.