How do I only allow number input into my C# Console Application?

try this code snippet

string _val = "";
Console.Write("Enter your value: ");
ConsoleKeyInfo key;

do
{
    key = Console.ReadKey(true);
    if (key.Key != ConsoleKey.Backspace)
    {
        double val = 0;
        bool _x = double.TryParse(key.KeyChar.ToString(), out val);
        if (_x)
        {
            _val += key.KeyChar;
            Console.Write(key.KeyChar);
        }
    }
    else
    {
        if (key.Key == ConsoleKey.Backspace && _val.Length > 0)
        {
            _val = _val.Substring(0, (_val.Length - 1));
            Console.Write("\b \b");
        }
    }
}
// Stops Receving Keys Once Enter is Pressed
while (key.Key != ConsoleKey.Enter);

Console.WriteLine();
Console.WriteLine("The Value You entered is : " + _val);
Console.ReadKey();

This MSDN article explains how to read characters one at a time in a console window. Test each character as it is input with the Char.IsNumber() method, and reject those characters that fail the test.