C# Refactoring gigantic switch statement for ordering with LINQ

Question

My problem is repetitive code: a not so DRY switch statement.

So I have a table with 12 columns that can be ordered by descending or ascending on click. My current solution is the use of a switch statement that checks which column was clicked.

The sortable properties:

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This is the page where if a user clicks on a head the table gets ordered:

enter image description here

The SortByColumn property comes in a string. SortAscending boolean comes in from a @Html.CheckBoxFor.

enter image description here

You see where this is going? I have 12 columns that can be ordered, so this switch can get very lengthy and unmaintainable. So my question is, is it possible to refactor this with reflection or in some other way?

your question fit better to http://codereview.stackexchange.com/ — ale, Jun 17 '15 at 10:01
For dynamic ordering, I always recommend to at least look at this : http://stackoverflow.com/questions/41244/dynamic-linq-orderby-on-ienumerablet — Raphaël Althaus, Jun 17 '15 at 10:02
Perhaps use a dictionary that maps strings to Func delegates? — Matthew Watson, Jun 17 '15 at 10:30

score 2 · Accepted Answer · answered Jun 17 '15 at 10:52

The OrderBy function works by letting you return the property it should sort on, it will be called foreach item in the list.

Instead of hardcoding it, we can use reflection instead:

public ActionResult Index(AgentReportViewModel vm)
{
    var b = Agent.GetAgents();
    vm.Agents = vm.SortAscending 
        ? b.OrderBy(x => GetValueByColumn(x, vm.SortByColumn))
        : b.OrderByDescending(x => GetValueByColumn(x, vm.SortByColumn));
    return View(vm);
}

public object GetValueByColumn<T>(T x, string columnStr)
{
    // Consider caching the property info, as this is a heavy call.
    var propertyInfo = x.GetType().GetProperty(columnStr);    
    return propertyInfo.GetValue(x, null);
}

score 1 · Answer 2 · answered Jun 17 '15 at 10:55

You can use expression trees for this scenario.

public static Func<Agent, object> GetOrderBySelector(string propertyName)
{
    var parameter = Expression.Parameter(typeof(Agent), "a");
    var property = Expression.Property(parameter, propertyName);
    // a => a.PropertyName is a unary expression
    var unaryExpression = Expression.Convert(property, typeof(object));
    // Create the lambda for the unary expression with the given property 
    // information and compile to return the actual delegate.
    return Expression.Lambda<Func<Agent, object>>(unaryExpression, parameter).Compile();
}

Usage:

b.OrderBy(vm.SortByColumn)

or

b.OrderByDescending(vm.SortByColumn)

Hope this helps.

score 0 · Answer 3 · edited May 23 '17 at 11:44

0

Try this:

var SortByColumnStr = "Answer"; //Dynamic string
var propertyInfo = typeof(Agent).GetProperty(SortByColumnStr);    
List<Agent> b.OrderBy(x => propertyInfo.GetValue(x, null));

Reference: https://stackoverflow.com/a/7265394/1660178

edited May 23 '17 at 11:44

Community

1
1

answered Jun 17 '15 at 10:05

sangram parmar

8,462
2
23
47

score 0 · Answer 4 · answered Jun 17 '15 at 11:08

0

Take look at System.Linq.Dynamic (NuGet Package Available).

Then you can do just:

string sortingString = string.Format("{0} {1}",vm.OrderByColumn, vm.SortAscending ? "ASC" : "DESC");
vm.Agents = Agent.GetAgents().OrderBy(sortingString).ToList();

answered Jun 17 '15 at 11:08

DonBaton

43
7

C# Refactoring gigantic switch statement for ordering with LINQ

4 Answers4