Guide to the Language

 Rectangular Arrays
There are two kinds of multi-dimensional arrays in C#: rectangular and 
jagged. A rectangular array has the same length of all sub-arrays and 
separates the dimensions using a comma.
string[,] x = new string[2, 2];
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As with single-dimensional arrays, they can either be filled in one at a 
time or all at once during the allocation.
x[0, 0] = "00"; x[0, 1] = "01";
x[1, 0] = "10"; x[1, 1] = "11";
string[,] y = { { "00", "01" }, { "10", "11" } };
 Jagged Arrays
Jagged arrays are arrays of arrays, and they can have irregular dimensions. 
The dimensions are allocated one at a time and the sub-arrays can 
therefore be allocated to different sizes.
string[][] a = new string[2][];
a[0] = new string[1]; a[0][0] = "00";
a[1] = new string[2]; a[1][0] = "10"; a[1][1] = "11";
It is possible to assign the values during the allocation.
string[][] b = { new string[] { "00" },
new string[] { "10", "11" } };
These are all examples of two-dimensional arrays. If you need more 
than two dimensions, more commas can be added for the rectangular 
array, or more square brackets for the jagged array.
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© Mikael Olsson 2020 
M. Olsson, C# 8 Quick Syntax Reference, 
https://doi.org/10.1007/978-1-4842-5577-3_7
CHAPTER 7
Conditionals
Conditional statements are used to execute different code blocks based on 
different conditions.
 If Statement
The if statement will execute only if the condition inside the parentheses 
is evaluated to true. The condition can include any of the comparison and 
logical operators.
// Get a random integer (0, 1 or 2)
int x = new System.Random().Next(3);
if (x < 1) {
System.Console.Write(x + " < 1");
}
To test for other conditions, the if statement can be extended by any 
number of else if clauses. Each additional condition will be tested only if 
all previous conditions are false.
else if (x > 1) {
System.Console.Write(x + " > 1");
}

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The if statement can have one else clause at the end, which will 
execute if all previous conditions are false.
else {
System.Console.Write(x + " == 1");
}
As for the curly brackets, they can be left out if only a single statement 
needs to be executed conditionally. However, it is considered good 
practice to include them since they improve readability.
if (x < 1)
System.Console.Write(x + " < 1");
else if (x > 1)
System.Console.Write(x + " > 1");
else
System.Console.Write(x + " == 1");