Contents tagged with Entity Framework
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Reverse Engineering EF Core Model and Data Validation Techniques
While working with ASP.NET Core and Entity Framework Core you need to create data model for your application. This calls for creating a DbContext class along with one or more entity classes. Luckily, EF Core allows you to reverse engineer the model from an existing database. To that end this article discusses how that can be accomplished.
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Two Ways of Handling Concurrency Violations in Entity Framework Code First
When you update an entity and call SaveChanges() to save the values back in the database, the existing values for that record are overwritten by the new entity values. This is the default behavior in entity framework code first. In a real world situation it is quite possible that database values might have got changed after you select them for modification. In such cases, your update operation might be overwriting changes made by someone else. This is concurrency violation. And it is important to detect if concurrency violation has occurred. You can then take some corrective action or at least inform the user about such a violation.
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Learn ASP.NET MVC in Thane. Registration started for October 2014 batches !
We will be conducting a 5 day intensive training program on ASP.NET MVC in the month of October 2014. Learn MVC5, EF6, Web API 2, VS2013 and more. Small batches, personal attention and real world examples. Registration has already started. In case you or your friends are interested to join please get in touch with us as soon as possible. The courses are conducted in Thane. You may read more details here.
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Wrapping multiple calls to SaveChanges() in a single transaction
When you make any additions, modifications and deletions to an Entity Framework DbSet and call SaveChanges(), EF starts a new transaction and executes all the INSERT, UPDATE and DELETE operations inside that newly created transaction. If the call to SaveChanges() succeeds the underlying transaction is committed, otherwise the transaction is rolled back. In some cases you may want that multiple calls to SaveChanges() be executed in the same transaction. Luckily, Entity Framework 6 provides an easy way to accomplish the same.
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What to do when SaveChanges() fails?
Beginners often ask this question - "What course of action should I take when a call to SaveChanges() fails?" The answer may vary based on a given situation and requirement. This article discusses one way to deal with the errors and shows how to display descriptive error messages to the end user and then rollback the changes made to the model.
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Cascading DropDownLists using "Eager Loading" on client side
One of my earlier articles shows how to create cascading DropDownLists by making Ajax calls to the MVC action methods. While that approach is quite common and popular recently a reader asked whether something similar can be done without making any Ajax calls. If you want to implement cascading dropdownlists purely on client side then you will need to "eagerly load" all the data needed by them at the time of loading the page. This data can be stored in a hidden field and used as and when needed. Obviously this technique is not suitable for huge amount of data since everything is loaded at once on the client side. However, if the data is small and you understand the implications of loading it in advance here is how you can accomplish the task.
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Creating Asynchronous Actions in ASP.NET MVC
Asynchronous actions allow you to handle more concurrent requests and can be implemented using async / await keywords. Asynchronous actions are useful in situations where you are performing some network operation such as calling a remote service. This article discusses asynchronous actions and also shows how to create them in an ASP.NET MVC.
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Performing Asynchronous Operations Using Entity Framework
Asynchronous programming involves executing operations in the background so that the main thread can continue its own operations. This way the main thread can keep the user interface responsive while the background thread is processing the task at hand. .NET framework introduced the async and await keywords that simplify asynchronous programming. Entity Framework 6.0 also supports asynchronous operations for querying and saving of the data. This article discusses the basics of using asynchronous operations of Entity Framework in desktop as well as web applications.
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Working with Stored Procedures in Entity Framework - Part 2
In Part 1 of this two part series, you learned to map stored procedures for the INSERT, UPDATE and DELETE operations in the entity framework designer. EF also allows you call arbitrary stored procedures from your code. This part of the article discusses how.
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Working with Stored Procedures in Entity Framework - Part 1
By default entity framework generates SELECT, INSERT, UPDATE, DELETE queries to perform the respective operations on the database. At times, however, you may want to deviate from this default behavior and use stored procedures for these operations. Additionally, you may want to call arbitrary stored procedures to perform some task at hand. To that end this two part article explains how stored procedures can be dealt with in Entity Framework.