LabVIEW
to create runtime library on labview front panel
Dropping controls, functions, and connecting them?
So basically you want to create LabVIEW in LabVIEW?
Of course possible, esp. if you limit the options. I'd go for a picture control...
Maybe you should tell a bit about the use case. I assume you want to provide an interface to the users of your application that enables them to "program" something?
Search LabVIEW like a graph! 
Certainly possible, but probably requires a lot of work, especially on the diagram side to generate the actual code. Easiest might be to parse it onto a math expression that can be digested by the formula parsing tools.
Note that Lego Mindstorms software is actually written in LabVIEW. Many (many!) years ago, there was a presentation by Greg McKaskle at NI Week about how it was done.
Can you explain in more details what problem you are trying to solve?
@Anu860 wrote:
but i just need one simple example code so i will implement the same.
That's a problem. A code example will be either trivial and fairly useless, or not simple.
I'd go (if I had to) for a picture control. You can draw anything in it, and probably can get something to drop on it (maybe with a lot of creativity). Then you need to detect clicks in an event structure, do hit detection (either on a list of coordinates, or on a second internal picture control storing ID's in stead of colors). Then animate (redraw) the object(s) accordingly.
Of course I (or my customer probably) would consider alternatives first, as this will be at least a few weeks of fulltime work (for me).
We can post examples, but you need to specify one or more subsets of the problem. On what part do you need help? Note that any non-trivial example will need some sort of architecture, rocketing development time sky high. I'm not ruling it out, but we all have (paid) work to do.
@Anu860 wrote:
I am writing a code to generate different modulation techniques like AM modulation,FM Modulation etc.
Now the theme is, user can develop it on my application by taking sine wave adding dc offset in it and then multiplying it with carrier signal to create actual Amplitude modulated signal. where user can drag and drop these components from library.
So this is just a linear sequence of processing steps. How about a horizontal arrangement of picture rings. For each step, the user can select a specific processing step (or "none", i.e. just a horizontal line). If there are only two possibilities, it could even be a boolean with two different images. On the code side, it would be trivial, just a sequence of case structures, one for each processing step. You could even have multiple such "trains" that get "merged" at certain points using specific graphic elements.
If there are more then two options, I'd consider one or two tree controls. That allows drag and drop, changing order, etc.
For instance, populate one tree control with available modules, the other is empty. Then the user can (almost OOTB) drag and drop the available modules in the empty tree. That's over simplified, but a hole lot easier then an actual graphical user interface like a LabVIEW diagram.
