Dynamically invoking a property with Reflection in .NET C#

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 property of a type in a referenced assembly.

In this post we saw how to invoke a constructor and here how to invoke a method of a Type.

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

public class Customer
{
	private string _name;

	public Customer() : this("N/A")
	{}

	public Customer(string name)
	{
		_name = name;
	}

        public int AccountValue { get; set; }
}

Build the solution and locate the compiled Domain.dll library. It should be located in either the Debug or Release folder within the bin folder depending on the compilation configuration in VS. Copy the .dll and put it somewhere else on your main drive where you can easily find it. We’re pretending that you got the library from another source but you for whatever reason cannot reference it at compile time. E.g. the source is loaded into your app as a plugin which follows some naming conventions so that your code can unwrap it and invoke its code.

Let’s see how we can get hold of the AccountValue property. First we’ll invoke the overloaded constructor:

string pathToDomain = @"C:\Studies\Reflection\Domain.dll";
Assembly domainAssembly = Assembly.LoadFrom(pathToDomain);
Type customerType = domainAssembly.GetType("Domain.Customer");
Type[] stringArgumentTypes = new Type[] { typeof(string) };
ConstructorInfo stringConstructor = customerType.GetConstructor(stringArgumentTypes);
object newStringCustomer = stringConstructor.Invoke(new object[] { "Elvis" });

Then we locate the AccountValue method and set its value. We also provide an object to represent the integer argument to the property. Keep in mind that properties are “normal” methods as we saw in this post so we need to supply an argument to the Set method:

PropertyInfo accountProperty = customerType.GetProperty("AccountValue");
accountProperty.SetValue(newStringCustomer, 1200);

Next we read the property value using the Get version:

int accountPropertyValue = Convert.ToInt32(accountProperty.GetValue(newStringCustomer));

‘accountPropertyValue’ will be 1200 as expected.

View all posts on Reflection here.

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About Andras Nemes
I'm a .NET/Java developer living and working in Stockholm, Sweden.

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