what are the most used interfaces in C#? [closed]

Answer 1

IQueryable<T>: lets you execute requests against queriable data sources. For example

        IQueryable<Project> projects = db.Projects;
        var selectedItems = projects
            .Where(x => x.Workers.Count() > 10 && x.Status != 1)
            .ToArray();

In this example filtering would be done on SQL Server (in involves tricky mechanics with translating Expression x => x.Workers.Count() > 10 && x.Status != 1 to SQL statements) So no need to write custom SQL commands to use all might of data source.

Also can be used not only with SQL, you can query objects or anything else, just find implementation of IQueryable<T>

Answer 2

INotifyPropertyChange : For data binding to UI classes in WPF, winforms and silverlight

Answer 3

The top two in my mind have to be ones with language support:

• IEnumerable<T> (and IEnumerable): for use with foreach and LINQ
• IDisposable: for resources requiring cleanup, used with using

Beyond that...

• IComparable<T> and IComparer<T>: for generalized sorting
• IEquatable<T> and IEqualityComparer<T>: for generalized equality
• IList<T> and ICollection<T>: for mutable collections
• IDictionary<T,K>: for lookup collections