If you implement one for each type, you can use separate classes, a generic base class and derived classes, or an abstract base class and derived classes. The page looks and works the same as it did before you changed the code to use the repository, and the other student pages also work the same. But the sorting and filtering work would then be done in memory on the web server.
In the rest of the class, all references to the database context are replaced by references to the appropriate repository, using var courses unitofwork. An alternative is to create derived classes for specific entity types and add specialized. For queries that return large volumes of data, this can be inefficient.
Save() context. Nstudent this query returns all of the student data because the repository executed the query without knowing about the search criteria. View(student) get studentedit5 public actionresult edit(int id) student student studentrepository.
The following illustration shows one way to conceptualize the relationships between the controller and context classes compared to not using the repository or unit of work pattern at all. The query isnt sent to the database until its converted into a collection using a method such as clause in the sql query that is sent to the database. However, in a complex application, this can result in a large number of such derived classes and specialized methods, which could be more work to maintain.
Try again, and if the problem persists, see your system administrator. Name ascending students students. The contoso university sample web application demonstrates how to create asp.
You have now implemented both the repository and unit of work patterns. You have used lambda expressions as method parameters in the generic repository. . For more information about the repository pattern, see the following resources there are many ways to implement the repository and unit of work patterns. The process of sorting, applying search criteria, and selecting a subset of the data for paging (showing only 3 rows in this case) is done in memory later when the in the previous version of the code (before you implemented the repository), the query is not sent to the database until after you apply the search criteria, when object, the query sent to sql server specifies the search string, and as a result only rows that meet the search criteria are returned, and no filtering needs to be done in memory.
Genericrepository(context) return courserepository public void save() context. You can use repository classes with or without a unit of work class. The query isnt sent to the database until its converted into a collection using a method such as clause in the sql query that is sent to the database. You can also build an abstraction layer into your database context class by using types for your entity sets. Genericrepository departmentrepository get if (this.
Get student public viewresult index(string sortorder, string currentfilter, string searchstring, int? Page) viewbag. That in turn means that only the selected entities are returned by the database. Asc,nplinq0 nvarchar(4000),plinq1 nvarchar(4000),plinq0nalex,plinq1nalex (the following tutorial explains how to examine queries sent to sql server. View(course) httppost validateantiforgerytoken public actionresult edit( bind(include courseid,title,credits,departmentid) course course) try if (modelstate. When the controller runs under a web server, it receives a repository that works with the entity framework.
Tentity getbyid(object id) return dbset. But in this case, the input to the expression is an iqueryable query dbsetif (filter ! Null) query query. The approach to implementing an abstraction layer shown in this tutorial is one option for you to consider, not a recommendation for all scenarios and environments. The controller now declares a class variable for an object that implements the the default (parameterless) constructor creates a new context instance, and an optional constructor allows the caller to pass in a context instance. That way, when a unit of work is complete you can call the method on that instance of the context and be assured that all related changes will be coordinated. Insertstudent(student student) context. The page looks and works the same as it did before your changes, and the other course pages also work the same. For some common errors and how to solve them, see in the previous tutorial you used inheritance to reduce redundant code in the entity classes. Next it applies the eager-loading expressions after parsing the comma-delimited list foreach (var includeproperty in includeproperties. Creating a repository class for each entity type could result in a lot of redundant code, and it could result in partial updates.Create a Generic Repository ... Linq; using System. ... Linq.Expressions; namespace ContosoUniversity. ... and a column to order the results by, and a string parameter ...