[FIXED] What is this type of C# coding syntax called and what is it doing?

Issue

For the below code, specifically the {} that don't seem connected to anything, what is the syntax called and what is it doing?

And when/why can I omit the () when using this syntax?

var a = new OpenApiSecurityRequirement() // Can I omit () and when/why?
{
    { // What is this doing?
        new OpenApiSecurityScheme
        {
            Reference = new OpenApiReference
            {
                Type = ReferenceType.SecurityScheme,
                Id="Bearer"
            }
        },
        new string[]{}
    } // What is this doing?
};

Solution

The outermost curly bracket is just a collection initialiser.

The inner curly bracket that "don't seem to be connected to anything" exists because the Add method of OpenApiSecurityRequirement takes two parameters.

Surely you have seen this syntax with Dictionarys:

new Dictionary<string, string>() {
    { "key1", "value1" },
    { "key2", "value2" },
    { "key3", "value3" }
};

Assuming this OpenApiSecurityRequirement, which is also an IDictionary, your code is just that, but the inner curly brackets are written on multiple lines. The dictionary has one entry. The key is the OpenApiSecurityScheme, and the value is the empty string array.

And yes, the parentheses can be omitted.

Desugared:

var a = new OpenApiSecurityRequirement();
a.Add(
    new OpenApiSecurityScheme
        {
            Reference = new OpenApiReference
            {
                Type = ReferenceType.SecurityScheme,
                Id="Bearer"
            }
        }, 
    new string[]{}
);

Answered By - Sweeper

Answer Checked By - Senaida (PHPFixing Volunteer)