How to implement a dictionary for our C# application?
Implementing a dictionary in the context of a school application may sound complex at first, but I promise you that by the end of this guide it will be much clearer. Let's explore how to create a dictionary in C# that makes sense for representing object types within a school, such as schools, courses, and more.
How do we create the dictionary in C#?
The purpose is to set up a structure where the keys are strings and the values are a series of objects of a generic type known as IEnumerable<ObjectSchoolBase>. To do this, we will start by defining the basis of our method.
public Dictionary<string, IEnumerable<ObjectSchoolBase>> GetDictionaryObject(){ var dictionary = new Dictionary<string, IEnumerable<ObjectSchoolBase>>();
var school = new ObjectSchool(); dictionary .Add("School", new[] { school });
var courses = new List<Course>(); dictionary.Add("Courses", courses.Cast<ObjectSchoolBase>());
return dictionary;}
What is the logic behind the use of dictionaries?
The concept here is simple: associate a key with a value, where the key is a string (e.g., "School") and the value is a list of objects. However, due to compatibilities and inheritances in C#, we cannot map a list of a type directly to a list of a parent type without performing an explicit cast.
Why use IEnumerable and casting?
Choosing IEnumerable as a generic type makes our code more flexible.
- Flexibility: We expose a generic list interface that can accept different types of collections.
- Casting: Converting explicitly, via
Cast<T>, ensures that the types are compatible, since polymorphism is not enough to perform this conversion implicitly.
How do we handle common mistakes with dictionary keys?
One of the classic traps when manipulating dictionaries is the duplication of keys. In C#, each key must be unique. If you try to add a key that already exists, the program will throw an exception.
For example:
dictionary.Add("Courses", courses.Cast<ObjectSchoolBase>());dictionary.Add("Courses", otherCourseGroup.Cast<ObjectSchoolBase>());
Final state of the dictionary?
The final dictionary should have a structure where each object type is grouped under a specific key, making it easier to retrieve and manipulate collections within our school application.
I encourage you to continue exploring the possibilities of manipulating data and structures, as having this initial clarity will allow you to create more robust and efficient programs. Don't stop here and keep learning about C# and collection management!
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