Projects each element of a sequence to an IEnumerable, and flattens the resulting sequences into one sequence. This is useful if you want to store only a part of the information from each object in a sequence. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. Correlates the elements of two sequences based on equality of keys and groups the results. In the following example, assume that a product object (p) contains many fields and methods, and that you are only interested in creating a sequence of objects that contain the product name and the unit price. Now, I have a problem that I have to assign these data into several TextBoxes. 2023 All Rights Reserved. public string GetCustomerName(IEnumerable<Customer> customers, int id) { return customers.First(c => c.Id == id).Name; } Solution 3. Thanks for the amazing blog post. Ive not verified, but I suspect any Linq method which returns IEnumerable will be lazily evaluated, whereas all others will necessarily evaluate the collection to return a fully initialized object, i.e. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. It's elements do, so you'll need to identify the element in the collection from which you want to read those values. You can iterate as much or as little as you want. By definition, value types have a value, and even uninitialized variables of value types must have a value. More info about Internet Explorer and Microsoft Edge, Covariance and Contravariance in Generics, Microsoft.Extensions.Configuration.Memory.MemoryConfigurationProvider, Microsoft.Extensions.DependencyInjection.IServiceCollection, Microsoft.Extensions.DependencyInjection.ServiceCollection, Microsoft.Extensions.DiagnosticAdapter.Internal.ProxyEnumerable, Microsoft.Extensions.DiagnosticAdapter.Internal.ProxyList, Microsoft.Extensions.FileProviders.Composite.CompositeDirectoryContents, Microsoft.Extensions.FileProviders.IDirectoryContents, Microsoft.Extensions.FileProviders.Internal.PhysicalDirectoryContents, Microsoft.Extensions.FileProviders.NotFoundDirectoryContents, Microsoft.Extensions.Logging.FilterLoggerSettings, Microsoft.Extensions.Logging.Internal.FormattedLogValues, Microsoft.Extensions.Primitives.StringTokenizer, Microsoft.Extensions.Primitives.StringValues, System.Activities.Presentation.ContextItemManager, System.Activities.Presentation.Model.ModelItemCollection, 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System.Collections.Generic.IReadOnlyDictionary, System.Collections.Generic.IReadOnlyList, System.Collections.Generic.IReadOnlySet, System.Collections.Generic.PriorityQueue.UnorderedItemsCollection, System.Collections.Generic.SortedDictionary, System.Collections.Generic.SortedDictionary.KeyCollection, System.Collections.Generic.SortedDictionary.ValueCollection, System.Collections.Generic.SortedList, System.Collections.Generic.SynchronizedCollection, System.Collections.Generic.SynchronizedReadOnlyCollection, System.Collections.Immutable.IImmutableDictionary, System.Collections.Immutable.IImmutableList, System.Collections.Immutable.IImmutableQueue, System.Collections.Immutable.IImmutableSet, System.Collections.Immutable.IImmutableStack, System.Collections.Immutable.ImmutableArray, System.Collections.Immutable.ImmutableArray.Builder, System.Collections.Immutable.ImmutableDictionary, System.Collections.Immutable.ImmutableDictionary.Builder, System.Collections.Immutable.ImmutableHashSet, 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System.Data.Objects.ObjectParameterCollection, System.Data.Services.Client.DataServiceQuery, System.Data.Services.Client.DataServiceResponse, System.Data.Services.Client.QueryOperationResponse, System.Diagnostics.ActivityTagsCollection, System.DirectoryServices.AccountManagement.PrincipalCollection, System.DirectoryServices.AccountManagement.PrincipalSearchResult, System.DirectoryServices.AccountManagement.PrincipalValueCollection, System.IdentityModel.Tokens.SecurityKeyIdentifier, System.IO.Enumeration.FileSystemEnumerable, System.IO.Packaging.PackagePartCollection, System.IO.Packaging.PackageRelationshipCollection, System.Net.Http.Headers.HeaderStringValues, System.Net.Http.Headers.HttpHeadersNonValidated, System.Net.Http.Headers.HttpHeaderValueCollection, System.Net.NetworkInformation.GatewayIPAddressInformationCollection, System.Net.NetworkInformation.IPAddressCollection, System.Net.NetworkInformation.IPAddressInformationCollection, System.Net.NetworkInformation.MulticastIPAddressInformationCollection, System.Net.NetworkInformation.UnicastIPAddressInformationCollection, System.Reflection.Metadata.AssemblyFileHandleCollection, System.Reflection.Metadata.AssemblyReferenceHandleCollection, System.Reflection.Metadata.BlobBuilder.Blobs, System.Reflection.Metadata.CustomAttributeHandleCollection, System.Reflection.Metadata.CustomDebugInformationHandleCollection, System.Reflection.Metadata.DeclarativeSecurityAttributeHandleCollection, System.Reflection.Metadata.DocumentHandleCollection, System.Reflection.Metadata.EventDefinitionHandleCollection, System.Reflection.Metadata.ExportedTypeHandleCollection, System.Reflection.Metadata.FieldDefinitionHandleCollection, System.Reflection.Metadata.GenericParameterConstraintHandleCollection, System.Reflection.Metadata.GenericParameterHandleCollection, System.Reflection.Metadata.ImportDefinitionCollection, System.Reflection.Metadata.ImportScopeCollection, 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System.Security.Cryptography.X509Certificates.X509Certificate2Collection, System.Security.Cryptography.X509Certificates.X509ChainElementCollection, System.Security.Cryptography.X509Certificates.X509ExtensionCollection, System.Security.Principal.IdentityReferenceCollection, System.ServiceModel.Channels.MessageHeaders, System.ServiceModel.Channels.MessageProperties, System.ServiceModel.Channels.UnderstoodHeaders, System.ServiceModel.Configuration.CustomBindingElement, System.ServiceModel.Configuration.ServiceModelExtensionCollectionElement, System.ServiceModel.Dispatcher.IMessageFilterTable, System.ServiceModel.Dispatcher.MessageFilterTable, System.ServiceModel.Dispatcher.MessageQueryTable, System.ServiceModel.Dispatcher.XPathMessageFilterTable, System.ServiceModel.ExtensionCollection, System.ServiceModel.IExtensionCollection, System.Text.Json.JsonElement.ArrayEnumerator, System.Text.Json.JsonElement.ObjectEnumerator, System.Text.RegularExpressions.CaptureCollection, System.Text.RegularExpressions.GroupCollection, System.Text.RegularExpressions.MatchCollection, System.Web.ModelBinding.ModelBinderDictionary, System.Web.ModelBinding.ModelStateDictionary, System.Web.Services.Description.BasicProfileViolationCollection, System.Windows.Controls.ColumnDefinitionCollection, System.Windows.Controls.RowDefinitionCollection, System.Windows.Data.XmlNamespaceMappingCollection, System.Windows.Documents.DocumentReferenceCollection, System.Windows.Documents.DocumentStructures.FigureStructure, System.Windows.Documents.DocumentStructures.ListItemStructure, System.Windows.Documents.DocumentStructures.ListStructure, System.Windows.Documents.DocumentStructures.ParagraphStructure, System.Windows.Documents.DocumentStructures.SectionStructure, System.Windows.Documents.DocumentStructures.StoryFragment, System.Windows.Documents.DocumentStructures.StoryFragments, System.Windows.Documents.DocumentStructures.TableCellStructure, System.Windows.Documents.DocumentStructures.TableRowGroupStructure, System.Windows.Documents.DocumentStructures.TableRowStructure, System.Windows.Documents.DocumentStructures.TableStructure, System.Windows.Documents.PageContentCollection, System.Windows.Documents.TableCellCollection, System.Windows.Documents.TableColumnCollection, System.Windows.Documents.TableRowCollection, System.Windows.Documents.TableRowGroupCollection, System.Windows.Documents.TextElementCollection, System.Windows.Forms.NumericUpDownAccelerationCollection, System.Windows.Markup.INameScopeDictionary, System.Windows.Media.Animation.ClockCollection, System.Windows.Media.Animation.TimelineCollection, System.Windows.Media.CharacterMetricsDictionary, System.Windows.Media.Effects.BitmapEffectCollection, System.Windows.Media.FamilyTypefaceCollection, System.Windows.Media.FontFamilyMapCollection, System.Windows.Media.GeneralTransformCollection, System.Windows.Media.GradientStopCollection, System.Windows.Media.Imaging.BitmapMetadata, System.Windows.Media.LanguageSpecificStringDictionary, System.Windows.Media.Media3D.GeneralTransform3DCollection, System.Windows.Media.Media3D.MaterialCollection, System.Windows.Media.Media3D.Model3DCollection, System.Windows.Media.Media3D.Point3DCollection, System.Windows.Media.Media3D.Transform3DCollection, System.Windows.Media.Media3D.Vector3DCollection, System.Windows.Media.Media3D.Visual3DCollection, System.Windows.Media.PathFigureCollection, System.Windows.Media.PathSegmentCollection, System.Windows.Media.TextEffectCollection, System.Workflow.Activities.OperationParameterInfoCollection, System.Workflow.ComponentModel.ActivityCollection, System.Xml.Xsl.Runtime.XmlQueryNodeSequence, System.Xml.Xsl.Runtime.XmlQuerySequence, ToFrozenDictionary(IEnumerable, Func, IEqualityComparer), ToFrozenDictionary(IEnumerable, Func, Func, IEqualityComparer), ToFrozenSet(IEnumerable, IEqualityComparer), ToFrozenSet(IEnumerable, IEqualityComparer, Boolean), ToImmutableArray(IEnumerable), ToImmutableDictionary(IEnumerable, Func), ToImmutableDictionary(IEnumerable, Func, IEqualityComparer), ToImmutableDictionary(IEnumerable, Func, Func), ToImmutableDictionary(IEnumerable, Func, Func, IEqualityComparer), ToImmutableDictionary(IEnumerable, Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents. For example, to read the values on the first element: Or if you want to get a collection of all the Count values, something like this: You're operating on a collection of elements, not a single element. The default equality comparer is used to compare keys. Thanks for contributing an answer to Stack Overflow! Some of the answers above suggest using IList instead of IEnumerable. Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value. Or you need to iterate over it to get the current value from collection. TResult>, IEqualityComparer), Intersect(IEnumerable, IEnumerable), Intersect(IEnumerable, IEnumerable, IEqualityComparer), IntersectBy(IEnumerable, IEnumerable, Func), IntersectBy(IEnumerable, IEnumerable, Func, IEqualityComparer), Join(IEnumerable, IEnumerable, Func, Func, Func), Join(IEnumerable, IEnumerable, Returns an enumerator that iterates through the collection. Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. It's possible to access the list with Linq using the namespace. Func, Func, IEqualityComparer, AsEnumerable() in C - To cast a specific type to its IEnumerable equivalent, use the AsEnumerable() method. The index arguments form the left side of the assignment, and the value is the right side of the expression. To get a list, call ToList () after casting. Your email address will not be published. Filters a sequence of values based on a predicate. As we saw in the previous section, in order for a data structure to support a foreach loop, it must be a subtype of either IEnumerable or IEnumerable<T>, where T is the type of the elements in the data structure. Sorts the elements of a sequence in ascending order. Nice intro article. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value. IEnumerable contains a single method that you must implement when implementing this interface; GetEnumerator, which returns an IEnumerator object. Looking for job perks? Creates a List from an IEnumerable. The element initializers can be a simple value, an expression, or an object initializer. A question for the readers or the author what if I want to avoid lazy load with yield for the IEnumerable, because of the side effects you mention (external state variables affected) BUT I am worried about memory consumption? Well, thats a bunch of code the computer didnt have to execute. What was the actual cockpit layout and crew of the Mi-24A? Sorts the elements of a sequence in descending order. How can I do this? IEnumerable is the base interface for collections in the System.Collections.Generic namespace such as List, Dictionary, and Stack and other generic collections such as ObservableCollection and ConcurrentStack. Converts a generic IEnumerable to a generic IQueryable. Some Linq methods may be lazily evaluated (Select, Where, OrderBy? Constructs an immutable dictionary from an existing collection of elements, applying a transformation function to the source keys. Proudly powered by WordPress. Returns the maximum value in a generic sequence. Implementing IEnumerator also requires IDisposable to be implemented, which you will see in this example. Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. Returns a specified range of contiguous elements from a sequence. Func, Func, Func, Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, LINQ's Distinct() on a particular property, Returning IEnumerable vs. IQueryable, How to Sort a List by a property in the object. IEnumerable<T> contains a single method that you must implement when implementing this interface; GetEnumerator, which returns an IEnumerator<T> object. How to Enumerate Using Enum.GetValues (Type type) Before we enumerate our DayOfWeek enum we need to get the values into an enumerable type. Returns the last element of a sequence that satisfies a condition, or a specified default value if no such element is found. Note that the individual object initializers are enclosed in braces and separated by commas. This post will discuss how to convert an enum to a list in C#. Casts the elements of an IEnumerable to the specified type. Returns distinct elements from a sequence by using a specified IEqualityComparer to compare values. The . }. For a simple iterator like the one Ive written, thats technically okay to do. Dynamic languages allow for a lot of flexibility in typing sometimes too much. The above is identical to writing: The following example combines the concepts of object and collection initializers. Produces a sequence of tuples with elements from the two specified sequences. Query expressions make frequent use of anonymous types, which can only be initialized by using an object initializer, as shown in the following declaration. (There are multiple ways to approach something like this, depending on the expected size of the collection and what youre trying to track.). The IEnumerable itself doesn't have Count, Start, or End.It's elements do, so you'll need to identify the element in the collection from which you want to read those values. Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty. The following example shows two simple collection initializers: The following collection initializer uses object initializers to initialize objects of the Cat class defined in a previous example. Returns the number of elements in a sequence. Suppose, I have 10 TextBoxes named txtSomething_1,txtSomething_2 and like this txtSomething_10. Hopefully this overview helps you avoid running into issues when you create or consume IEnumerable in your own code (which is extremely likely, as theyre everywhere in C#). Produces the set difference of two sequences according to a specified key selector function. Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence. The next time a value is expected, the function will continue executing statements after the yield return until it hits another yield return (or a yield break, or the end of the function block). See: How to get item from IEnumerable collection using its index in C#? How to combine independent probability distributions? Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function. To prove it, run the following code in LINQPad. What does the power set mean in the construction of Von Neumann universe? Invokes a transform function on each element of a sequence and returns the maximum Int64 value. I have an application containing class which also contains a method that returns IEnumerable<string> Now, I can get the data from IEnumerable<string>. How to get the index of an element in an IEnumerable? IEqualityComparer), Last(IEnumerable, Func), LastOrDefault(IEnumerable), LastOrDefault(IEnumerable, TSource), LastOrDefault(IEnumerable, Func), LastOrDefault(IEnumerable, Func, TSource), LongCount(IEnumerable, Func), Max(IEnumerable, IComparer), Max(IEnumerable, Func), Max(IEnumerable, Func), Max(IEnumerable, Func), Max(IEnumerable, Func), Max(IEnumerable, Func>), Max(IEnumerable, Func>), Max(IEnumerable, Func>), Max(IEnumerable, Func>), Max(IEnumerable, Func>), Max(IEnumerable, Func), Max(IEnumerable, Func), MaxBy(IEnumerable, Func), MaxBy(IEnumerable, Func, IComparer), Min(IEnumerable, IComparer), Min(IEnumerable, Func), Min(IEnumerable, Func), Min(IEnumerable, Func), Min(IEnumerable, Func), Min(IEnumerable, Func>), Min(IEnumerable, Func>), Min(IEnumerable, Func>), Min(IEnumerable, Func>), Min(IEnumerable, Func>), Min(IEnumerable, Func), Min(IEnumerable, Func