Check if user input is a number
<p>I want to check if user's input is a number. If yes I want the function to keep running else  want to alert him and run it again. </p>

<pre><code>Console.WriteLine(String.Concat("choose your action" ,Environment.NewLine ,
                                "1.Deposit", Environment.NewLine,
                                "2.Withdraw", Environment.NewLine,
                                "3.CheckAccount"));
string c = Console.ReadLine();
int value = Convert.ToInt32(c);

if (value==char.IsLetterOrDigit(value)) //&lt;----- no good why?
{
    switch (value)
    {
        case 1:
            Deposit();
            return;
        case 2:
            Withdraw();
            return;
        case 3:
            CheckAccount();
            return;
    }
}
</code></pre>
