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I Don’t Miss ViewState

May 16, 2010 Dave Swersky 3 comments

I’ve been working with ASP.NET MVC for the last year and I don’t miss webforms.  The one thing about webforms I miss the least is ViewState.

It’s a Hack

Hidden HTML fields were never intended to hold so much data.  Persisting data in the page this way is Ugly, Expensive, Confusing, and Hard to Test.

It’s Ugly

ViewState is this ugly blob of Base-64 encoded data:

 <input type=”hidden” name=”__VIEWSTATE”
  value=”aHR0cDovL3d3dy5jb2Rlcm9zZXR0YS5jb20vYmFsbHB1enpsZQ==” />

It’s Expensive

ViewState is processed on every postback. This means it has to be sent, parsed, processed, updated, and re-sent with every request.  Not good for performance!

It’s Confusing

I can’t tell you how many StackOverflow and forums posts I’ve seen about dynamic controls and ViewState.  If you don’t add dynamic controls at just the right point in the page lifecycle, ViewState breaks.

It Uses Magic Strings (So It’s Hard to Test)

ViewState["MyMagicString"] is a typo-prone way to address data.  Strongly-typed Views in ASP.NET MVC are so much easier to work with and much more testable.

The MVC Way

MVC doesn’t even try to match ViewState as a feature.  ViewState is a stateful paradigm layered on top of a fundamentally stateless protocol: HTTP.  Rather than the hybridized hack of packing a huge encoded graph into a hidden field, MVC says:

“If you want to persist state, do it on the server using a Model.”

You can use Session state or TempData on the server and javascript or cookies at the client to store pointers, but actual data should be persisted by one thing- the Model.  The MVC rendering pipeline relies on Models (or ViewModels) to retain and provide the data that populate Views.  If you change the state of a control, the data is updated in and persisted through the Model, preferably by a loosely-coupled persistence implementation.  This is a much cleaner, architecturally sound method for dealing with state over a stateless delivery protocol.

Categories: Uncategorized Tags:

LINQ Aggregate Queries: Multiple Group By Columns

November 12, 2009 Dave Swersky Leave a comment

I recently had the need to SUM a column grouped by two other columns. Here’s the view:

SELECT SolutionID, EventName, EventDuration
FROM Events

I needed this:

SELECT SolutionID, EventName, SUM(EventDuration) EventTotal
FROM Events
GROUP BY SolutionID, EventName

Here’s the LINQ:

var events = from e in summary
   group e by new { e.SolutionID, e.EventDetail } into g
   let TotalMinutes = g.Sum(x => x.EventDuration)
   orderby TotalMinutes descending
   select new EventSummary
     {
          SolutionID = g.Key.SolutionID,
          Name = g.Key.EventDetail,
          Seconds = TotalMinutes,
          Minutes = TotalMinutes / 60.0,
          Hours = (TotalMinutes / 60.0) / 60.0
     };

The magic is in line 2:

   group e by new { e.SolutionID, e.EventDetail } into g

You can group by as many columns as you need with that little nugget. Using the anonymous type feature in C# 3.0 you can group on as many columns as you need. Enjoy!

Categories: LINQ, Uncategorized Tags: , ,