IEnumerable In .net

IEnumerable Interface

.NET Framework 1.1

Exposes the enumerator, which supports a simple iteration over a collection.

For a list of all members of this type, see IEnumerable Members.

First it is an interface.  The definition according to MSDN is


Exposes the enumerator, which supports a simple iteration over a non-generic
  collection.



Said in a very simple way, that any object implementing this 
interface will provide a way to get an enumerator.  An enumerator is 
used with the foreach as one example.



A List implements the IEnumerable interface.  



    // This is a collection that eventually we will use an Enumertor to loop through
    // rather than a typical index number if we used a for loop.
    List<string> dinosaurs = new List<string>();

    dinosaurs.Add("Tyrannosaurus");
    dinosaurs.Add("Amargasaurus");
    dinosaurs.Add("Mamenchisaurus");
    dinosaurs.Add("Deinonychus");
    dinosaurs.Add("Compsognathus");

    Console.WriteLine();

    // HERE is where the Enumerator is gotten from the List<string> object
    foreach(string dinosaur in dinosaurs)
    {
        Console.WriteLine(dinosaur);
    }

    // You could do a 
    for(int i = 0; i < dinosaurs.Count; i++)
    {
        string dinosaur = dinosaurs[i];

        Console.WriteLine(dinosaur);
    }

Classes that Implement IEnumerable

Class	Description
Array	Provides methods for creating, manipulating, searching, and sorting arrays, thereby serving as the base class for all arrays in the common language runtime.
ArrayList	Implements the IList interface using an array whose size is dynamically increased as required.
AttributeCollection	Represents a collection of attributes.
BaseChannelObjectWithProperties	Provides a base implementation of a channel object that wants to provide a dictionary interface to its properties.
BaseCollection	Provides the base functionality for creating data-related collections in the System.Windows.Forms namespace.
BindingContext	Manages the collection of BindingManagerBase objects for any object that inherits from the Control class.
BitArray	Manages a compact array of bit values, which are represented as Booleans, where true indicates that the bit is on (1) and false indicates the bit is off (0).
Cache	Implements the cache for a Web application. This class cannot be inherited.
CaptureCollection	Represents a sequence of capture substrings. CaptureCollection returns the set of captures done by a single capturing group.
CheckedListBox.CheckedIndexCollection	Encapsulates the collection of indexes of checked items (including items in an indeterminate state) in a CheckedListBox.
CheckedListBox.CheckedItemCollection	Encapsulates the collection of checked items (including items in an indeterminate state) in a CheckedListBox control.
ClerkMonitor	Contains a snapshot of all Clerks active in the process.
CodeNamespaceImportCollection	Represents a collection of CodeNamespaceImport objects.
CollectionBase	Provides the abstract (MustInherit in Visual Basic) base class for a strongly typed collection.
ComboBox.ObjectCollection	Represents the collection of items in a ComboBox.
Control.ControlCollection	Represents a collection of Control objects
ControlCollection	Provides a collection container that enables ASP.NET server controls to maintain a list of their child controls.
CookieCollection	Provides a collection container for instances of the Cookie class.
CredentialCache	Provides storage for multiple credentials.
DataBindingCollection	Provides a collection of DataBinding objects for an ASP.NET server control. This class cannot be inherited.
DataColumnMappingCollection	Contains a collection of DataColumnMapping objects.
DataGridColumnCollection	A collection of DataGridColumn derived column objects that represent the columns in a DataGrid control. This class cannot be inherited.
DataGridItemCollection	Represents a collection of DataGridItem objects in a DataGrid control.
DataKeyCollection	Represents a collection that contains the key field of each record in a data source. This class cannot be inherited.
DataListItemCollection	Represents the collection of DataListItem objects in the DataList control. This class cannot be inherited.
DataTableMappingCollection	A collection of DataTableMapping objects. This class cannot be inherited.
DataView	Represents a databindable, customized view of a DataTable for sorting, filtering, searching, editing, and navigation.
DataViewManager	Contains a default DataViewSettingCollection for each DataTable in a DataSet.
DataViewSettingCollection	Contains a read-only collection of DataViewSetting objects for each DataTable in a DataSet.
DesignerCollection	Represents a collection of designers.
DictionaryBase	Provides the abstract (MustInherit in Visual Basic) base class for a strongly typed collection of key-and-value pairs.
DirectoryEntries	Contains the children (child entries) of an entry in Active Directory.
EventDescriptorCollection	Represents a collection of EventDescriptor objects.
EventLogEntryCollection	Defines size and enumerators for a collection of EventLogEntry instances.
Evidence	Defines the set of information that constitutes input to security policy decisions. This class cannot be inherited.
GridItemCollection	Contains a collection of GridItem objects.
GroupCollection	Represents a collection of captured groups. GroupCollection returns the set of captured groups in a single match.
Hashtable	Represents a collection of key-and-value pairs that are organized based on the hash code of the key.
HtmlTableCellCollection	A collection of HtmlTableCell objects that represent the cells in a single row of an HtmlTable control. This class cannot be inherited.
HtmlTableRowCollection	A collection of HtmlTableRow objects that represent the rows of an HtmlTable control. This class cannot be inherited.
HttpSessionState	Provides access to session-state values as well as session-level settings and lifetime management methods.
HttpStaticObjectsCollection	Provides a static objects collection for the StaticObjects property.
HybridDictionary	Implements IDictionary by using a ListDictionary while the collection is small, and then switching to a Hashtable when the collection gets large.
ImageList.ImageCollection	Encapsulates the collection of Image objects in an ImageList.
InternalDataCollectionBase	Provides the base functionality for creating collections.
KeyInfo	Represents an XMLDSIG <KeyInfo> element.
LinkLabel.LinkCollection	Represents the collection of links within a LinkLabel control.
ListBox.ObjectCollection	Represents the collection of items in a ListBox.
ListBox.SelectedIndexCollection	Represents the collection containing the indexes to the selected items in a ListBox.
ListBox.SelectedObjectCollection	Represents the collection of selected items in the ListBox.
ListDictionary	Implements IDictionary using a singly linked list. Recommended for collections that typically contain 10 items or less.
ListItemCollection	A collection of ListItem objects in a list control. This class cannot be inherited.
ListView.CheckedIndexCollection	Represents the collection containing the indexes to the checked items in a list view control.
ListView.CheckedListViewItemCollection	Represents the collection of checked items in a list view control.
ListView.ColumnHeaderCollection	Represents the collection of column headers in a ListView control.
ListView.ListViewItemCollection	Represents the collection of items in a ListView control.
ListView.SelectedIndexCollection	Represents the collection containing the indexes to the selected items in a list view control.
ListView.SelectedListViewItemCollection	Represents the collection of selected items in a list view control.
ListViewItem.ListViewSubItemCollection	Represents a collection of ListViewItem.ListViewSubItem objects stored in a ListViewItem.
ManagementObjectCollection	Represents different collections of management objects retrieved through WMI. The objects in this collection are of ManagementBaseObject-derived types, including ManagementObject and ManagementClass. The collection can be the result of a WMI query executed through a ManagementObjectSearcher object, or an enumeration of management objects of a specified type retrieved through a ManagementClass representing that type. In addition, this can be a collection of management objects related in a specified way to a specific management object - in this case the collection would be retrieved through a method such as GetRelated. The collection can be walked using the ManagementObjectCollection.ManagementObjectEnumerator and objects in it can be inspected or manipulated for various management tasks.
MatchCollection	Represents the set of successful matches found by iteratively applying a regular expression pattern to the input string.
Menu.MenuItemCollection	Represents a collection of MenuItem objects.
MessageQueue	Provides access to a queue on a Message Queuing server.
MethodDataCollection	Represents the set of methods available in the collection.
NameObjectCollectionBase	Provides the abstract (MustInherit in Visual Basic) base class for a collection of associated String keys and Object values that can be accessed either with the key or with the index.
NameObjectCollectionBase.KeysCollection	Represents a collection of the String keys of a collection.
OdbcDataReader	Provides a way of reading a forward-only stream of data rows from a data source. This class cannot be inherited.
OdbcErrorCollection	Collects all errors generated by the OdbcDataAdapter. This class cannot be inherited.
OdbcParameterCollection	Represents a collection of parameters relevant to an OdbcCommand as well as their respective mappings to columns in a DataSet. This class cannot be inherited.
OleDbDataReader	Provides a way of reading a forward-only stream of data rows from a data source. This class cannot be inherited.
OleDbErrorCollection	Collects all errors generated by the .NET Framework Data Provider for OLE DB. This class cannot be inherited.
OleDbParameterCollection	Represents a collection of parameters relevant to an OleDbCommand as well as their respective mappings to columns in a DataSet.
OracleDataReader	Provides a way of reading a forward-only stream of data rows from a data source. This class cannot be inherited.
OracleParameterCollection	Represents a collection of parameters relevant to an OracleCommand as well as their respective mappings to columns in a DataSet. This class cannot be inherited.
PagedDataSource	Encapsulates the properties of the DataGrid control that allow it to perform paging. This class cannot be inherited.
PermissionSet	Represents a collection that can contain many different types of permissions.
PrinterSettings.PaperSizeCollection	Contains a collection of PaperSize objects.
PrinterSettings.PaperSourceCollection	Contains a collection of PaperSource objects.
PrinterSettings.PrinterResolutionCollection	Contains a collection of PrinterResolution objects.
PropertyCollection	Contains the properties of a DirectoryEntry.
PropertyDataCollection	Represents the set of properties of a WMI object.
PropertyDescriptorCollection	Represents a collection of PropertyDescriptor objects.
PropertyGrid.PropertyTabCollection	Contains a collection of PropertyTab objects.
QualifierDataCollection	Represents a collection of QualifierData objects.
Queue	Represents a first-in, first-out collection of objects.
ReadOnlyCollectionBase	Provides the abstract (MustInherit in Visual Basic) base class for a strongly typed read-only collection.
RepeaterItemCollection	Represents a collection of RepeaterItem objects in the Repeater control. This class cannot be inherited.
ResourceReader	Enumerates .resources files and streams, reading sequential resource name and value pairs.
ResourceSet	Stores all the resources localized for one particular culture, ignoring all other cultures, including any fallback rules.
ResXResourceReader	Enumerates XML resource (.resx) files and streams, and reads the sequential resource name and value pairs.
SchemaNameCollection	Contains a list of the schema names that the SchemaFilter property of a DirectoryEntries object can use.
SearchResultCollection	Contains the SearchResult instances that the Active Directory hierarchy returned during a DirectorySearcher query.
SecurityCallers	Provides an ordered collection of identities in the current call chain.
SelectedDatesCollection	Encapsulates a collection of System.DateTime objects that represent the selected dates in a Calendar control. This class cannot be inherited.
SharedPropertyGroupManager	Controls access to shared property groups. This class cannot be inherited.
SignedInfo	Contains information about the canonicalization algorithm and signature algorithm used for the XML signature.
SortedList	Represents a collection of key-and-value pairs that are sorted by the keys and are accessible by key and by index.
SqlCeErrorCollection	Collects all errors generated by the .NET Compact Framework Data Provider for SQL Server CE. This class cannot be inherited.
SqlCeParameterCollection	Collects all parameters relevant to a SqlCeCommand as well as their respective mappings to DataSet columns.
SqlDataReader	Provides a means of reading a forward-only stream of rows from a SQL Server database. This class cannot be inherited.
SqlErrorCollection	Collects all errors generated by the .NET Framework Data Provider for SQL Server. This class cannot be inherited.
SqlParameterCollection	Represents a collection of parameters relevant to a SqlCommand as well as their respective mappings to columns in a DataSet. This class cannot be inherited.
Stack	Represents a simple last-in-first-out collection of objects.
StateBag	Manages the view state of ASP.NET server controls, including pages. This class cannot be inherited.
StatusBar.StatusBarPanelCollection	Represents the collection of panels in a StatusBar control.
String	Represents text; that is, a series of Unicode characters.
StringCollection	Represents a collection of strings.
StringDictionary	Implements a hashtable with the key strongly typed to be a string rather than an object.
TabControl.TabPageCollection	Contains a collection of TabPage objects.
TableCellCollection	Encapsulates a collection of TableHeaderCell and TableCell objects that make up a row in a Table control. This class cannot be inherited.
TableRowCollection	Encapsulates a collection of TableRow objects that represent a single row in a Table control. This class cannot be inherited.
TempFileCollection	Represents a collection of temporary files.
ToolBar.ToolBarButtonCollection	Encapsulates a collection of ToolBarButton controls for use by the ToolBar class.
TraceListenerCollection	Provides a thread-safe list of TraceListener objects.
TreeNodeCollection	Represents a collection of TreeNode objects.
TypeConverter.StandardValuesCollection	Represents a collection of values.
ValidatorCollection	Exposes an array of IValidator references. This class cannot be inherited.
XmlNamedNodeMap	Represents a collection of nodes that can be accessed by name or index.
XmlNamespaceManager	Resolves, adds and removes namespaces to a collection and provides scope management for these namespaces. This class is used by the XsltContext and XmlReader classes.
XmlNode	Represents a single node in the XML document.
XmlNodeList	Represents an ordered collection of nodes.
XmlSchemaCollection	Contains a cache of XML Schema definition language (XSD) and XML-Data Reduced (XDR) schemas. This class cannot be inherited.

Remarks

Notes to Implementers: 
IEnumerable must be implemented to support the ForEach semantics of Microsoft Visual Basic. COM classes that allow enumerators also implement this interface.

Requirements

Namespace: System.Collections
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework
Assembly: Mscorlib (in Mscorlib.dll)