The methods in this class provide an implementation of the standard query operators for querying data sources that implement ienumerable. Its potentially annoying to have an extension method like that turn up on almost every type. Obtain a linq standard ienumerable sequence from a datatable so standard query oper ators may be. For example, for table productionorder viewable fields are orderno, factory and country. So think about whether this is really something that you want frequently. We can use the different querying capabilities of the linq.
Taking the boredom out of querying joseph albahari. Asenumerable simply returns the source sequence as an object of type ienumerable. Before counting items one by one, it first checks whether the ienumerable can be cast to icollection or icollection. In linq tutorial we covered a topics like linq lambda expressions, aggregate functions, operators. Ienumerable and iqueryable are used for data manipulation in linq from the database and collections. Asenumerable basically changes the compile time type of given type that implements ienumerable to ienumerable itself. With linq to sql, you first create an objectrelational mapping at design time either manually or by using the linq to sql tools in visual studio in visual studio. The ouside part that is the query after asenumerable operator is executed as linq toobjects. Paolo pialorsi marco russo programming microsoft linq in microsoft. There are over 50 standard query operators available in linq that provide different functionalities like filtering, sorting, grouping, aggregation. Linq, the same data query can be written in a readable colorcoded form like the following one mentioned below that too in a very less time. Linq is an acronym which stands for language integrated query. Here x is an input parameter followed by operator and next to the operator there is an expression that adds numeric 10 to the input variable x. In the following example, customers represents a specific table.
Employeeinfo, it initiates to fetch all the records from the database using the automated generated query. An object that implements ienumerable can be enumerated through an object that imple. It has many qualities that make it suitable for development for users at most all levels. Languageintegrated query linq is the name for a set of technologies. Asenumerable the asenumerable ienumerable method has no effect other than to change the compiletime type of source from a type that implements ienumerable to ienumerable itself. Asenumerable ienu merable can be used to choose between query implementations when a sequence implements ienumerable but also has a different set of public query methods available. Icollection is implemented by list, dictionary, hashset, array t and others.
Net collections, and any other format for which a linq. I want to use linq, so i can join some tables runtime. Asenumerable returns its argument typed as ienumerable. The following code example demonstrates how to use select to. Net and java apis for file formats natively work with docx, xlsx, ppt, pdf, images and more. If so, it simply returns value of its count property. An operator is a special word that tells linq what kind of query to perform, such as checking whether two values are equal. To query datatable using linq we call the asenumerable method of the datatable. This part discussed the index and range types, syntax, compilation, and how to apply them with linq for any type that implements ienumerable. Jul 24, 2014 the inside part that is the query before asenumerable operator is executed as linq tosql 2. This must be interpreted or compiled in order to get the result. Language integrated query or linq is the collection of standard query operators which provides query facilities into. Operators can run into the hundreds, but in most cases youll perform the majority of tasks using only a few standard operators. Following is the syntax of using linq asenumerable method to convert give list items to ienumerable type.
Logic was very simple, pass table name to method and method should return list of fields that is marked as viewable. Oftype filters the elements of a sequence based on a type. So the output would increment the numeric 10 to the x variable which was the input parameter on the lefthand side of the expression. The content posted here is free for public and is the content of its poster. In linq, lambda expression is a function without a name. The language integrated part means that linq is part of programming language syntax. For getting the data from the database, i have created a table named employee that has some data and looks like. Linq, datavisualization and asenumerable codeproject. Part 17 asenumerable and asqueryable in linq youtube. Companyname the result of this query is a list of strings. With just a single one, its probably a minor irritation at most, but in the future you may find yourself coming up with more this object or this t extension methods, and either youll start to get a very clogged up intellisense. Cast casts the elements of a sequence to a given type. In addition to these linq to dataset operators, once you have called the asenumerable operator, you can call. Though it is not as readable as a linq query it is equally important as the linq query and gets convert to lambda internally.
Asenumerable ienu merable method has no effect other than to change the compiletime type of source from a type that implements ienumerable to ienumerable itself. Recently i was trying to optimize one of my old code and wanted to use linq for this. Todictionary creates a dictionary from a sequence onetoone. Asenumerable the above diagram clearly demonstrates how linq gets functioned. It is a concept which integrates a query language by offering a consistent model for working with data across various kinds of data sources and formats. Asenumerable ienu merable can be used to choose between query implementations when a sequence implements ienumerable but also has a different set of public. Asenumerable method in linq is used to cast or convert given type into its ienumerable type. I am trying to get a row if it has the desired specific value, otherwise get the first or default. There are over 50 standard query operators available in linq that provide different functionalities like filtering, sorting, grouping, aggregation, concatenation, etc. Advantages of linq linq offers a host of advantages and among them the foremost is its powerful. The example code also shows the implementation of asenumerable in the.
Also learn the differences between ienumerable and. Enumerable class and its main operations, implementing your own extension which generates a stream of data. Standard query operators in linq are actually extension methods for the ienumerable and iqueryable types. Oct 31, 2014 in linq also, we have to follow the same points.
Enumerable class and its main operations, implementing your. The ouside part that is the query after asenumerable operator is executed as linqtoobjects. After calling asenumerable the data source can no longer be queried and it falls back to a simplistic give me. Linq tutorial for beginners and experienced with examples.
Net community by providing forums questionanswer site where people can help each other. Linq is required as it bridges the gap between the world of data and world of objects. For example, given a generic class table that implements ienumerable and has its own methods such as where, select, and selectmany, a call. Asenumerable splits the linq into two parts before query and after query. Net languageintegrated query for relational data krzysztof mossakowski. The standard query operators are general purpose methods that follow the linq pattern and enable you to express traversal, filter, and projection operations over data in any. Linq asenumerable method with what is linq, introduction, syntax, projection. I have made use of the following table customers with the schema as follows. Help with asenumerable, linq solutions experts exchange. This mean the delegate it receives is an expression tree instead of a method to invoke. Jun 07, 2016 linq is an acronym for language integrated query, which is descriptive for where its used and what it does. Tsource the type of the elements of source tresult the type of the value returned by selector source a sequence of values to invoke a transform function on selector a transform function to apply to each source element.
When you have an ienumerable collection, you typically access it through queries or a foreachloop. Ancy black books for professionals by professionals companion. I try to bind my data which is stored in a dataset to a chart. Language integrated query linq uses an amazing array of operators. You write your queries against the objects, and at runtime linq to sql handles the communication with the database.
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