C# loop loops the first statement three times before moving to the second statement

I have wrote this do-while loop in a console app in C#:

do 
{
    ThisHelp.ShowMenu();
    userChoice = (char) Console.Read();
    ThisHelp.Helpon(userChoice);
}while(ThisHelp.IsValid(userChoice) == false);

The method ThisHelp.ShowMenu() has just a bunch of Write + WriteLine methods, which are asking the user to type a number from 1 to 8. The method ThisHelp.Helpon() has a switch that depending on the user input passed, shows a different piece of text. The method ThisHelp.IsValid just checks that the user input is a number from 1 to 8.

Here's the problem: After the user writes a number and presses ENTER, the first statement of the loop executes 3 times before the second statement executes at least once. Why is this happening?

edit: Here is the code of the ThisHelp.IsValid method, as requested:

public bool IsValid(char ch)
{
   if (ch < '1' | ch > 8 & ch != 'q') return false;
   else return true;
}