The do-while statement executes a statement or a block of statements while a specified Boolean expression evaluates to true. Because that expression is evaluated after each execution of the loop, a do-while loop executes one or more times.
This differs from the while loop, which executes zero or more times.

using System;

int i = 0;

do
{
    int j = i;

    do
    {
        Console.Write($" {j} ");

        j++;
    }
    while (j < i + 10);

    Console.WriteLine();

    i += 10;
}
while (i < 100);

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