delphi check if there is only numbers code example

Example 1: how to check if something is only numbers in delphi

if TryStrToInt(Edit1.Text, Value) then
  DoSomethingWithTheNumber(Value)
else
  HandleNotANumberError(Edit1.Text);

Example 2: how to validate if the text in edit has numbers in and to show a message if it has in delphi

// Taking OP question obsessively literally, this 
// function doesn't allow negative sign, decimals, or anything
// but digits
function IsValidEntry(s:String):Boolean;
var
  n:Integer;
begin
  result := true;
  for n := 1 to Length(s) do begin
    if (s[n] < '0') or (s[n] > '9') then
    begin
       result := false;
       exit;
    end;
  end;
end;