When do we use reflection in .net

Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services. Privacy policy. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. Reflection namespace. Security is another consideration when dealing with reflection. Member access keywords like public , protected , and private are merely suggestions at compile time.

When we use reflection, we will almost certainly hit runtime exceptions that we may have caught at compile time. Remember, in most cases, we should consider other approaches before reflection. The runtime uses BindingFlags as a lookup filter to change what we should be searching to find our target members.

The flags will vary based on each use case, so pay attention to which ones we use. The first scenario is invoking a method, only knowing its name. The dynamic invocation of methods is typical across many libraries. We can also invoke private methods and retrieve their value. Notice how this code is very similar to our first example, except now we are passing a BindingFlags. NonPublic value into our GetMethod call. Generics are a powerful feature of C and.

NET in general. Developers can create reusable constructs. Consuming generically-defined code at development time is straightforward. You can parse the corresponding metadata tables to look through these items:. Late bindings can also be achieved through reflection.

To illustrate, you might not know which assembly to load during compile time. In this instance, you can ask the user to enter the assembly name and type during run time so the application can load the appropriate assembly. With the System. Assembly type, you can get three static types which allow you to load an assembly directly:. When you consider that an assembly is a logical DLL or EXE and a manifest is a detailed overview of an assembly, then it makes sense that a PE portable executable file for CTS would have the extension of.

Within the PE file is mainly metadata, which contains a variety of different tables such as a:. Other uses for Reflection include constructing symbol tables, to determine which fields to persist and through serialization. At Stackify, we think C and. NET Core will be big in , so brush up on your C skills by checking out some of our other resources on topics such as.

Daily development should not be modifying this code. Daily development should use the reflective methods to simplify daily development tasks. We want our code to be easy to follow, and Reflective code is not always the most intuitive code to understand at first glance. Without a doubt the hard-coded option is easier to follow than the reflective version.

Anyone can look at the hard-coded version and immediately tell what is going on. The reflective version will probably take a senior developer a second look to figure out. However, the hard-coded version is tedious code. Depending on the number of properties being mapped, more and more errors are likely to be introduced.

In the long run, this results in more code that has to be hand written. While the reflective code may be hard to follow, it does not need to be referenced very often to be useful. With the hard-coded implementation, you have to write a similar method for every type that you want to map. This is a tedious proposition indeed! With the reflective implementation, this one method can handle the process of mapping any object in your system. For the observant reader, this is far from the most optimized implementation for the reflective version.

We will go over the reflective version in more detail later and discuss various ways to optimize. As mentioned earlier, the hard coded version is often tedious, and tedious code is often error-prone. You can well imagine the potential for introducing bugs by having to iterate through, and explicitly set, each property in an object. This can quickly get out of hand. Bugs from assigning the wrong value to the wrong property are easy to introduce and difficult to track down.

It is much easier to write a single line of code to handle the mapping and then move on to more important tasks such as implementing business logic and meeting deadlines. A call like DataMapper. CopyTo data, ui is easy to understand and quick to write. Not everyone will get reflective code right the first time, but this is the beauty of consistency. If the implementation that everyone is using is inefficient or has a logic problem, you have only to correct it in one place.

If there are multiple hard coded implementations, some will, no doubt, be done as efficiently as possible. Some will, to be sure, be free from all logic problems, but at least some implementations will have problems that will need to be addressed. Reflective code is much easier to reuse. If the code is widely reused, then we have fewer places to correct when there is a problem found.

Performance is always a concern. There are some simple steps that we can take to eke the best performance out of our reflective code. Whenever you make a Reflection call, make it count. Cache the output so that it can be reused. If there is any chance that you are going to need a method or a property more than once, store the return value so that you can use it later without having to make the call again.

This is also an example where multi threading can give you the perception of performance improvement. This does not provide any benefit for the web UI, but can be very beneficial for a traditional windows application. CopyTo is the reflective MapData that we saw earlier.

We also want to avoid calling GetProperty altogether when we are truly interested in every property. We start by checking to see if our collection of properties has already been loaded into a hash table. If they have, then we use this previously-loaded list.

If not, we go ahead and load the details into the hash table. This will allow us to avoid the GetProperty calls altogether. If we are copying from one object to another of the same type, we dramatically reduce the number of reflection calls. If we call this method multiple times with the same set of objects, we reduce the reflective even more. Here we first check to see if the Hash table already has a list of properties for our object.

If it does then we have nothing to do. If not, we load the properties into a generic list to be added to the hash table. The biggest change we have here is in the calls to the LoadProperties method. If the properties are already loaded, this will have no effect. If they are not, this method will load the properties for us. Once our properties are loaded into the hash table, we can safely pull them out of the generic list instead of making repeated calls to GetProperties or GetProperty.