SaveChangesAsync : Saves the entity changes asynchronously. FirstAsync ; context. Assume the following: The Room table will hold a list of rooms for a hotel. The RoomProducts table will hold a list of products in Room , and refers to Room. Id as a foreign key. The records in all three tables will definitely have a relational record in them. Let me write a LINQ query that maps all tables with join and pulls the matching records.
Rooms join products in context. RoomProducts on room. Id equals products. RoomParentId join brands in context. Brands on products. Id equals brands. Conclusion In this blog post, we have seen some of the areas where we can concentrate to improve the performance of LINQ to Entities. Please have a look and use them in your application development: ASP.
Share this post:. Selvam M. Comments 10 Diwas Poudel. July 29, at pm. August 5, at am. It motivates us to create more useful blogs. Thanks, Selvam M. August 2, at pm. Jacob Ford. October 2, at am. December 7, at am. Victor Imoru. December 4, at am. April 19, at pm. May 4, at am. Hi Sandeep, Yes we can use.
Popular Now. Be the first to get updates. Subscribe RSS feed. Privacy Policy Terms of Use. All Rights Reserved. You will get all configuration abilities available with attribute configuration. These two approaches are interchangeable in its abilities. This kind of configuration is done through the class MappingSchema. With Fluent approach you can configure only things that require it explicitly. All other properties will be inferred by linq2db:. In this example we configured only three properties and one association.
We let linq2db to infer all other properties which have to match with column names. However, other associations will not get configured automatically.
There is a static property LinqToDB. Default which may be used to define a global configuration. This mapping is used by default if no mapping schema provided explicitly. The other way is to pass instance of MappingSchema into constructor alongside with connection string. This approach involves no attributes at all. In this case linq2db will use POCO's name as table name and property names as column names with exact same casing, which could be important for case-sensitive databases.
This might seem to be convenient, but there are some restrictions: linq2db will not infer primary key even if class has property called "ID"; it will not infer nullability of string properties as there is no way to do so; and associations will not be automatically configured.
And there will be no association with Vendor. All this mapping is done through a DataConnection class:. We call the base constructor with the "Northwind" parameter.
Make sure you always wrap your DataConnection class in our case DbNorthwind in a using statement. This is required for proper resource management, like releasing the database connections back into the pool. More details. However, sometimes getting all the fields is too wasteful so we want only certain fields, but still use our POCOs; something that is challenging for libraries that rely on object tracking, like LINQ to SQL.
Rather than concatenating strings we can 'compose' LINQ expressions. In the example below the final SQL will be different if onlyActive is true or false, or if searchFor is not null. A lot of times we need to write code that returns only a subset of the entire dataset.
We expand on the previous example to show what a product search function could look like. Keep in mind that the code below will query the database twice. Once to find out the total number of records, something that is required by many paging controls, and once to return the actual data.
This assumes we added a Category class, just like we did with the Product class, defined all the fields, and registered it in our DbNorthwind data access class. In the previous example we assign an entire Category object to our product, but what if we want all the fields in our Product class, but we don't want to specify every field by hand?
Unfortunately, we cannot write this:. The query above assumes the Product class has a constructor that takes in a Category object.
The query above won't work, but we can work around that with the following query:. One caveat with this approach is that if you're using it with composed queries see example above the select Build part has to come only in the final select. At some point we will need to add a new Product to the database. One way would be to call the Insert extension method found in the LinqToDB namespace; so make sure you import that. This inserts all the columns from our Product class, but without retrieving the generated identity value.
There is also InsertOrReplace that updates a database record if it was found by primary key or adds it otherwise. If you need to insert only certain fields, or use values generated by the database, you could write:.
Updating records follows similar pattern to Insert. NET Framework version 3. Relational data appears as a collection of two-dimensional tables relations or flat files , where common columns relate tables to each other. In LINQ to SQL, the data model of a relational database is mapped to an object model expressed in the programming language of the developer.
When the database returns the results, LINQ to SQL translates them back to objects that you can work with in your own programming language. You can also search Microsoft Docs for specific issues, and you can participate in the LINQ Forum , where you can discuss more complex topics in detail with experts. Programming Guide Provides steps for mapping, querying, updating, debugging, and similar tasks. Samples Provides links to Visual Basic and C samples.
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