No, C# does not have extension properties. Extension properties are a feature that is present in some other languages, such as F#. However, they are not currently supported in C#.

In C#, you can achieve a similar effect by using extension methods. Extension methods are static methods that are defined on a type, but they can be called as if they were instance methods on the type. This allows you to add new functionality to an existing type without having to modify the type itself.

For example, the following code shows how to use an extension method to add a new property to the string type:

C#

public static class StringExtensions
{
    public static int Length(this string str)
    {
        return str.Length;
    }
}

string myString = "Hello, world!";

int myStringLength = myString.Length(); // This calls the extension method

This code will print the length of the myString variable to the console.

While extension methods cannot achieve the same exact functionality as extension properties, they can be a useful way to add new functionality to existing types.