Validation of an ID - loops

Question

Im creating a code that will validate if the user enter all digits as the user is entering an ID. I have a code but I cant figure out how to complete it.
var name:string;
i,c:integer;
ch:char;
begin
name:Edit1.text;
n:length(name);
for i := 0 to n do
begin
ch:=name[i];
//not code//
if ch= any digits then showmessage invalid else showmessage valid;

Answer 1

Your code snippet does not match your question description. You ask about ID validation, but then show code for name validation instead.
In any case, try something like the following:
function IsDigit(c: Char): boolean; inline;
begin
Result := (c >= '0') and (c <= '9');
{
Or Result := CharInSet(c, ['0'..'9']);
Or Result := Character.IsDigit(c);
Or Result := c.IsDigit();
}
end;
Name check:
var
name: String;
i: Integer;
ch: Char;
begin
name := Edit1.Text;
n := Length(name);
for i := 1 to n do
begin
ch := name[i];
if IsDigit(ch) then
begin
ShowMessage('invalid');
Exit;
end;
end;
ShowMessage('valid');
end;
ID check:
var
id: String;
i: Integer;
ch: Char;
begin
id := Edit2.Text;
n := Length(id);
if n = 0 then
begin
ShowMessage('invalid');
Exit;
end;
for i := 1 to n do
begin
ch := id[i];
if not IsDigit(ch) then
begin
ShowMessage('invalid');
Exit;
end;
end;
ShowMessage('valid');
end;
Alternatively:
var
id: Integer; // or Int64
begin
if not TryStrToInt(Edit2.Text, id) then // or TryStrToInt64()
ShowMessage('invalid')
else
ShowMessage('valid');
end;