The for statement executes a statement or a block of statements while a specified Boolean expression evaluates to true.

using System;

for (var i = 0; i < 100; i += 10)
{
    for (var j = i; j < i + 10; j++)
    {
        Console.Write($" {j} ");
    }

    Console.WriteLine();
}

Output:

0  1  2  3  4  5  6  7  8  9 
 10  11  12  13  14  15  16  17  18  19 
 20  21  22  23  24  25  26  27  28  29 
 30  31  32  33  34  35  36  37  38  39 
 40  41  42  43  44  45  46  47  48  49 
 50  51  52  53  54  55  56  57  58  59 
 60  61  62  63  64  65  66  67  68  69 
 70  71  72  73  74  75  76  77  78  79 
 80  81  82  83  84  85  86  87  88  89 
 90  91  92  93  94  95  96  97  98  99