Give names to Key and Value in C# Dictionary to improve code readability

Question

In C# struct, we can know clearly the purpose of a variable by it's name. For example,

public struct Book
{
    public string title;
    public string author;
}

Then, i know b.title is a type of string and it's referring to title.

However in C# dictionary, we can only specify the type

Dictionary<string,string> d

How can i make the code more readable such that the key of the dictionary is type of string and it is referring to title, and the value is type of string and it is referring to author? That means, other people can easily know that d["J.R.R. Tolkien"] is a wrong use of the dictionary when reading the code.

EDIT @mike z suggested to use a variable name titleToAuthor to help readability. But my real issue is that in the code there are nested dictionary. E.g.

Dictionary<string, Dictionary<string, string>>, 
or even 3 levels   
Dictionary<string, Dictionary<string , Dictionary< string , string[] >>>. 

We want to keep to convenience of using Dictionary without creating our own class but at the same time we need some way to improve the readability

Answer 1

As suggested by @ScottDorman you could define a new Type TitleAuthorDictionary that derives from Dictionary<string, string>, like so:

public class TitleAuthorDictionary : Dictionary<string, string>
{
    public new void Add(string title, string author)
    {
        base.Add(title, author);
    }

    public new string this[string title]
    {
        get { return base[title]; }
        set { base[title] = value; }
    }
}

You could then use the more readable Dictionary Collection, like this:

TitleAuthorDictionary dictionary = new TitleAuthorDictionary();
dictionary.Add("Title1", "Author1");
dictionary.Add(title: "Title2", author: "Author2");
dictionary["Title2"] = "Author3";

Answer 2

With .NET 6 and C# 10, you can now use global using directive to give type aliases in your project.

Give built-in types their aliases in one single place, e.g. GlobalUsings.cs.

global using Title = System.String;
global using Author = System.String;

Then use aliases for better readability in your dictionaries.

Dictionary<string, Dictionary<Title, Author>>