delphi 提取字符中的数字

Function Setstring(cString:string):string; {提取数字}
VAr
i:integer;
str:string;
begin
str:='';
For i:=1 to length(cString) do
begin
if Pos(cString[i],'0123456789.')<=0 then
break
else
Case cString[i] of
'.': str:=Str+'.';

'0': str:=Str+'0'; '1': str:=Str+'1'; '2': str:=Str+'2';
'3': str:=Str+'3'; '4': str:=Str+'4'; '5': str:=Str+'5';
'6': str:=Str+'6'; '7': str:=Str+'7';
'8': str:=Str+'8'; '9': str:=Str+'9';
end;
end;
Setstring:=str;
end;

如121545ADFDF.121 提取之后是 121545 函数中去掉break命令部份，结果便是：121545.121