http://www.dotnetperls.com/for

От друго място не съм чел.

В stackoverflow също има много информация, но там въпросите са по конкретен проблем, а не генерални като "цикли".

The c# for keyword indicates a loop in C#. The for loop executes a block of statements repeatedly until the specified condition returns false.

c# for Syntax:

for (variable initialization; condition; steps)
{
    //execute this code block as long as condition is satisfied 
}

As per the syntax on top of, the for loop contains 3 parts: format, conditional expression and steps, that square measure separated by a punctuation.

variable initialization: Declare & initialize a variable here which can be utilized in conditional expression and steps half.
condition: The condition may be a Boolean expression which can come either true or false.
steps: The steps defines the progressive or decremental half
Consider the subsequent example of an easy for loop.

for (int i = 0; i < 10; i++)
{
    Console.WriteLine("Value of i: {0}", i);
}

Основи на програмирането със C#  е точно по материала от Programming Basics като изключим методите.

To learn basics thoroughly is very crucial before learning the advanced concepts. The same apply with C# programming.