To find the average of 10 numbers using a while loop in C#, you can follow these steps:

• Initialize variables to keep track of the sum and count of numbers.
• Use a while loop to read 10 numbers from the user or any other source.
• Add each number to the sum and increment the count.
• After the loop, calculate the average by dividing the sum by the count.

Here's a C# program that demonstrates this:

using System;

class Program
{
    static void Main()
    {
        int count = 0;   // Initialize count to 0
        double sum = 0;  // Initialize sum to 0

        // Use a while loop to read 10 numbers
        while (count < 10)
        {
            Console.Write("Enter a number: ");
            if (double.TryParse(Console.ReadLine(), out double number))
            {
                sum += number; // Add the number to the sum
                count++;      // Increment the count
            }
            else
            {
                Console.WriteLine("Invalid input. Please enter a valid number.");
            }
        }

        // Calculate the average
        double average = sum / 10;

        // Display the average
        Console.WriteLine($"The average of the 10 numbers is: {average}");
    }
}

This program will keep prompting the user to enter a number until 10 valid numbers have been entered. It then calculates the average of these numbers and displays it to the user.