Write the clearest code you can, and then benchmark and profile to discover any performance problems. If you do have performance problems, you can experiment with different code to work out whether it’s faster or not (measuring all the time with as realistic data as possible) and then make a judgement call as to whether … Read more
Like this: if (list.Distinct().Skip(1).Any()) Or if (list.Any(o => o != list[0])) (which is probably faster)
I’ve fixed it myself now. It was a schoolboy error passing too many parameters to the CreateQuery(… ) call. Paste the following code into the Dynamic.cs file within the DynamicQueryable class for a dynamic Join extension method. You can find the source for the DynamicQuery sample project at http://code.msdn.microsoft.com/csharpsamples. Enjoy. public static IQueryable Join(this IQueryable … Read more
Where is the Find method on IEnumerable<T>? (Rhetorical question.) The Where and FirstOrDefault methods are applicable against multiple kinds of sequences, including List<T>, T[], Collection<T>, etc. Any sequence that implements IEnumerable<T> can use these methods. Find is available only for the List<T>. Methods that are generally more applicable, are then more reusable and have a … Read more
LINQ to entities: Video walkthroughs Channel 9 video Entity framework FAQ Entity framework performance I’ve got a lot more I tagged on Delicious.com.
Your status-codes are also a collection, so use Contains: var allowedStatus = new[]{ “A”, “B”, “C” }; var filteredOrders = orders.Order.Where(o => allowedStatus.Contains(o.StatusCode)); or in query syntax: var filteredOrders = from order in orders.Order where allowedStatus.Contains(order.StatusCode) select order;
Using closures and anonymous method: List<Item> myList = FetchDataFromDatabase(); decimal currentTotal = 0; var query = myList .OrderBy(i => i.Date) .Select(i => { currentTotal += i.Amount; return new { Date = i.Date, Amount = i.Amount, RunningTotal = currentTotal }; } ); foreach (var item in query) { //do with item }
This will loop through only once. Item biggest = items.Aggregate((i1,i2) => i1.ID > i2.ID ? i1 : i2); Thanks Nick – Here’s the proof class Program { static void Main(string[] args) { IEnumerable<Item> items1 = new List<Item>() { new Item(){ ClientID = 1, ID = 1}, new Item(){ ClientID = 2, ID = 2}, new … Read more
Take the type/ID checking out of the recursion, so just have a “give me all the controls, recursively” method, e.g. public static IEnumerable<Control> GetAllControls(this Control parent) { foreach (Control control in parent.Controls) { yield return control; foreach(Control descendant in control.GetAllControls()) { yield return descendant; } } } That’s somewhat inefficient (in terms of creating lots … Read more
This can be done as list.Sort( (emp1,emp2)=>emp1.FirstName.CompareTo(emp2.FirstName) ); The .NET framework is casting the lambda (emp1,emp2)=>int as a Comparer<Employee>. This has the advantage of being strongly typed. If you need the descending/reverse order invert the parameters. list.Sort( (emp1,emp2)=>emp2.FirstName.CompareTo(emp1.FirstName) );