This method actually performs an eager load of the category and, if needed, then we can modify the meaning of the eager loading of the category in one place. Suppose we have a site with product categories.
As most of the requests above also need to load the current category, then the query above is very popular on our site. In the method level, we cannot optimize much of how the query is run and how the results are returned, but we can save something by using a compiled query. This is also known as an explicitly compiled query. We define the compiled query as Func , which we can call later. Notice that query compiling happens in static scope, meaning that, once built, the query is used by all instances of the ApplicationDbContext class.
Current version of Entity Framework Core 2. To make the server use processors more effectively, we can run Entity Framework queries asynchronously. Actually, it adds one millimeter of overhead but we will win in better throughput. The first part defines the compiled query while the second bit makes use of the query object by passing the DbContext and the expected query parameter.
EDIT: after posting this, I had a few questions asking whether the performance gains were because SQL Server would cache the queries and hence give false positives. It's important to remember that when working with EF, there are 2 types of caching:.
Compiled queries target the 1st type, hence reducing the time to find the necessary query to execute against SQL. Just for completion, I decided to run the test multiple times and even changing the order that the commands were executed, i. This is one of the many new features introduced with the release of EF Core 2. Look out for follow ups on EF Core around:.
Our first step will be to write the Compile method, with signatures, having 2 input parameters of type context of entities and an integer type variable and returns us the list of the users. So our method will look like the following: By comparing the code above with the overload definitions of the Compile method previous image , we can see that we have TArg0 as our object context of entities, TArg1 is a filter condition and TResult is the output of the query or List of the Users, in our example.
Next, we will store the returned values in a delegate variable with the same signatures, as that of our Compile method, returning the list of users. Make sure that the variable we declare is of static type.
So our code becomes: This is it. Now we just need to create a method in order to call this query multiple times. This will invoke our delegate, that will further execute the Compile method. The point to note here is that for the very first time, this query may also take the same amount of time for execution, as it would have done in the case of a normal LINQ query. But subsequent calls will take much less time than the first call, since it will be already compiled by then and its cache plan will be used.
Another point to be mentioned, as per MSDN, starting with the. NET Framework 4. So this was about the concept of compiled queries in LINQ. Skip to main content.
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