Difference between array, arraylist, List, Hashtable, Dictionary and SortedList in c#

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Basic difference is that arrays are of fixed size. Whereas an ArrayList implements the list data structure and can dynamically grow. While arrays would be more performance that a list, a list would be far more flexible since you don't need to know the required size initially. Array - represents an old-school memory array - kind of like a alias for a normal type[] array. Can enumerate. Can't grow automatically. I would assume very fast insertion, retrieve and speed. ArrayList - automatically growing array. Adds more overhead. Can enum., probably slower than a normal array but still pretty fast. These are used a lot in .NET List - one of my favorites - can be used with generics, so you can have a strongly typed array, e.g. List . Other than that, acts very much like ArrayList. Hashtable - plain old hashtable. O(1) to O(n) worst case. Can enumerate the value and keys properties, and do key/val pairs. Dictionary - same as above only strongly typed via generics, such a...
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What is a ViewModel in ASP.NET MVC?

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A ViewModel basically acts as a single model object for multiple domain models, facilitating to have only one optimized object for View to render. Below diagram clearly express the idea of ViewModel in ASP.NET MVC:


There are multiple scenarios where using ViewModel becomes obvious choice. For example:

◾Parent-Child View Scenario
◾Reports where often aggregated data required
◾Model object having lookup data
◾Dashboards displaying data from multiple sources

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