How do I test if the first digit of an integer is a 7?

I have had the user enter an integer. I would like to test to see if the first digit is a 7 or not.

string enteredValue;
int number;
Console.WriteLine("Enter integer: ");
enteredValue = Console.ReadLine();

The test (to see if the first digit is a 7) can occur before or after I parse the string to an int. If the number is not a 7 have the following occur

Console.WriteLine("First digit was not 7");
Console.WriteLine(nRe-enter number ");