Examining class members through Types and Reflection in .NET C#

October 27, 2017 Leave a comment

Here we saw different ways to get hold of a Type. You can use the Type object to extract different ingredients of a class such as methods, properties, events etc. through various methods. The name of the object that these methods return ends with “Info”, like FieldInfo, MethodInfo etc.

These Info classes all derive from the MemberInfo abstract base class. The Type object also derives from MemberInfo.

Say you have the following Customer class:

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Examining a Type in .NET C#

June 1, 2017 Leave a comment

You can get hold of Types in a variety of ways. You can extract the Types available in an Assembly as follows:

Assembly executingAssembly = Assembly.GetExecutingAssembly();
Type[] typesAttachedToAssembly = executingAssembly.GetTypes();

Console.WriteLine("Types attached to executing assembly: ");
foreach (Type type in typesAttachedToAssembly)
{
	Console.WriteLine(type.FullName);
}

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An example of using the dynamic keyword in C# .NET

May 23, 2017 Leave a comment

The dynamic keyword in C# is similar to Reflection. It helps you deal with cases where you’re not sure of the concrete type of an object. However, you may expect the object to have a certain method that you can invoke at runtime. E.g. you have a framework that external users can write plugins for. You may set up a list of rules for the plugin to be valid, e.g. it must have a method called “Execute” and a property called “Visible”.

There are various ways you can solve this problem and one of them is dynamic objects. Using the dynamic keyword will turn off the automatic type checking when C# code is compiled. The validity of the code will only be checked at runtime.

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Dynamically finding the value of a static field with Reflection in .NET C#

May 18, 2017 Leave a comment

Say you do not have access to a .NET assembly at compile time but you want to execute code in it or read programmatic data from it.

One such scenario is when you’d like to extract some important field information from a class. Why would you ever need that?

Imagine that you have an application where people can upload their own plugins in the form of DLL’s. However, users do not programmatically build their own libraries in Visual Studio but rather use a GUI which will dynamically build a class file and compile it into a DLL based on the user’s selections on the GUI. This is possible if your users are not programmers or if the rules for the plugins are so complex that you wouldn’t want people to write their own solutions.

In such a scenario the class builder could write some important metadata in the form of static fields in the class, such as Version. E.g. if your app has multiple versions then the code generator would put the current version into the class so that your app can verify it. Then you can disallow plugins that were created with an older version of the app if the current version is not backward compatible.

Open Visual and create a new C# class library project called Domain. Add the following Customer class to it:

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Convert a dynamic type to a concrete object in .NET C#

May 16, 2017 Leave a comment

Dynamic objects in C# let us work with objects without compile time error checking in .NET. They are instead checked during execution. As a consequence we can’t use IntelliSense while writing the code to see what properties and functions an object has.

Consider the following Dog class:

public class Dog
{
	public string Name { get; }
	public string Type { get;}
	public int Age { get; }

	public Dog(string name, string type, int age)
	{
		Name = name;
		Type = type;
		Age = age;
	}
}

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Dynamically invoking a method with Reflection in .NET C#

May 11, 2017 Leave a comment

Say you do not have access to a .NET assembly at compile time but you want to run code in it. It’s possible to dynamically load an assembly and run code in it without early access.

Here we’ll see how to invoke a method of a type in a referenced assembly.

Open Visual Studio and create a new C# class library project called Domain. Add the following Customer class to it:

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Dynamically invoking a constructor with Reflection in .NET C#

May 9, 2017 1 Comment

Say you do not have access to a .NET assembly at compile time but you want to run code in it. It’s possible to dynamically load an assembly and run code in it without early access.

Here we’ll see how to invoke a constructor of a type in a referenced assembly.

Normally, if you have a direct reference to an assembly then you can simply initialise new objects using the ‘new’ keyword. In the absence of a direct reference this is not possible.

Open Visual Studio 2012/2013 and create a new C# class library project called Domain. Add the following Customer class to it:

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Examining the method body using Reflection in .NET C#

May 4, 2017 Leave a comment

In this short post we saw how to extract the members of a class: constructors, properties, methods etc. Even more exciting is the fact that you can peek into the body of a method. Well, not the plain text C# or VB code, but the Intermediate Language – MSIL version of it.

The MethodBody object represents, as the name suggests, the body of a method including the local variables and the MSIL instructions. MethodBody is available on classes that derive from the MethodBase class, which are methods and constructors – MethodInfo and ConstructorInfo.

Consider the following Customer class:

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Examining the Assembly using Reflection in .NET

May 2, 2017 Leave a comment

The CLR code of a project is packaged into an assembly. We can inspect a range of metadata from an assembly that also the CLR uses to load and execute runnable code: classes, methods, interfaces, enumerations etc.

In order to inspect an Assembly in a .NET project we’ll first need to get a reference to the assembly in question. There are various ways to retrieve an assembly, including:

Assembly callingAssembly = Assembly.GetCallingAssembly();
Assembly entryAssembly = Assembly.GetEntryAssembly();
Assembly executingAssembly = Assembly.GetExecutingAssembly();

…where Assembly is located in the System.Reflection namespace.

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Convert a dynamic type to a concrete object in .NET C#

February 7, 2017 Leave a comment

Dynamic objects in C# let us work with objects without compile time error checking in .NET. They are instead checked during execution. As a consequence we can’t use IntelliSense while writing the code to see what properties and functions an object has.

Consider the following Dog class:

public class Dog
{
	public string Name { get; }
	public string Type { get;}
	public int Age { get; }

	public Dog(string name, string type, int age)
	{
		Name = name;
		Type = type;
		Age = age;
	}
}

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