Month: September 2023

Getting all types that implement an interface

Using reflection, this is how we get all types that implement an interface with C# 3.0/.NET 3.5 with the least code, and minimizing iterations.

var type = typeof(IMyInterface);
var types = AppDomain.CurrentDomain.GetAssemblies()
    .SelectMany(s => s.GetTypes())
    .Where(p => type.IsAssignableFrom(p));

Basically, the least amount of iterations will always be:

loop assemblies  
 loop types  
  see if implemented.

References

https://stackoverflow.com/questions/26733/getting-all-types-that-implement-an-interface

When to use <> instead of ()

When we are suppose to use different parentheses in C#. When I run into a situation where i am trying to tell if i need to put <> or ().

The dumbed down version to explain is this;

() are for variables. <> are for types. If you have both, <> always comes first.

You would never has A(int). It would be A<int>. You’d also never have B<5>. It would always be B(5). And, rule two, you might have C<int>(5), but never C(5)<int>.

<> are used in generics.

Generics in C#

Generic is a type used to define a class, structure, interface, or method with placeholders to indicate that they can store or use one or more of the types. In C#, the compiler will replace placeholders with the specified type at compile time. We use generic frequently with collections.

Generics are useful for improving code reusability, type safety, and performance compared with non-generic types e.g. arraylist.

Here is a code sample;

//Generic example - using single generic type
public class Hospital<T>            //Here <T> is a a placeholder beside Hospital class
{
    private T Cases;                //Declared a variable named "Cases" of type T
    public Hospital(T value)        //Constructor take another variable named value
    {
        this.Cases = value;         //assinged received type to containting type "Cases"
    }

    public void Show()
    {
        Console.WriteLine(this.Cases);
    }
}

Let’s implement this in our .NET6 main class;

Console.WriteLine("Hello, World!");

//use Hospital class
Hospital<int> x = new Hospital<int>(100);       //replacing T with int
Hospital<string> y = new Hospital<string>("Hospital Cases");
x.Show();
y.Show();

We can use two generic types in a class;

//using two generic types
public class EliteHospital<T, U>            //Here <T> is a a placeholder beside Hospital class
{
    // PatientCount of type T
    public T? PatientCount {  get; set; }

    //Docotrs of U
    public U? Doctors { get; set; }  
}

This is how we can use this;

Console.WriteLine("Hello, World!");
//using EliteHospital class
EliteHospital<int, string> xx = new EliteHospital<int, string>();
xx.PatientCount = 100;
xx.Doctors = "Available";
Console.WriteLine(xx.PatientCount);
Console.WriteLine(xx.Doctors);

Console.WriteLine("Press any key to continue..");
Console.ReadKey();

Tree View control with JavaScript and Knockout for large trees

Most of the existing tree views used to crash my browser, they are making the naive mistake to load all the nodes in one shot. The simple solution was to load the nodes on demand, and when you open a node with thousands of children, and then you open another node which again has thousands of children, it is better to close the previous node and let go all their children than crash the browser.

Read more here;