By Julia Lerman
The DbContext API captures Entity Framework's (EF) most ordinarily used good points and projects, simplifying improvement with EF. This concise ebook indicates you ways to take advantage of the API to accomplish set operations with the DbSet classification, deal with switch monitoring and unravel concurrency conflicts with the switch Tracker API, and validate alterations for your information with the Validation API. With DbContext, one could question and replace information, even if you are operating with person items or graphs of items and their similar information. you will discover a number of C# code samples that can assist you start. All you would like is event with visible Studio and database administration fundamentals.
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Extra resources for Programming Entity Framework: DbContext: Querying, Changing, and Validating Your Data with Entity Framework
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Eager loading returns all data in a single query There is also a string-based overload of Include that just accepts the name of the property to include data for (Include(“Lodgings”) in our case). Previous versions of Entity Framework only included this string option. The string-based overload is problematic because it’s not strongly typed and therefore there is no compile-time checking of the parameter. This can lead to issues with mistyped property names or failing to update the Include call if the property is renamed in the future.
If you wanted to filter the contents of a navigation property you could do this after you’d brought everything into memory, using LINQ to Objects. However, if you are only interested in a subset of the contents, it may make sense to just bring the bits you are interested in into memory. Or if you just want a count, or some other calculation, it may make sense just to calculate the result in the database and not bring any of the data into memory. Once you’ve used Entry and Collection to drill into a collection navigation property, you can then use the Query method to get a LINQ query representing the contents of that property.
The query is expressed using a syntax that looks a little bit like SQL. You start by telling it what you want to select from (in our case, the Destinations set on our context). You give the set a name so that you can refer to it throughout the rest of the query (in our case that name is d). info use operators such as orderby, groupby, and where to define the query. Finally you specify what you want returned using the select operator. In our case we want the actual Destination objects returned, so we specify the name that we gave the set in the first line.