DELPHI数据转换Int64 to String

LPHI数据转换Int64 to String
编程实现
var
  ss,ss1:string;
  ss2:int64;
  tmp:string;
begin
  ss:='AB10000000001';
  tmp:=copy(ss,2,11);
  ss2:=tmp+1;        //如何转换使ss2:=10000000002
  ss1:=ss2;          //结果 ss1:='AB10000000002'
  showmessage(ss1);
end;

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[错误] Unit1.pas(118): Incompatible types: 'Int64' and 'String'
[错误] Unit1.pas(118): Incompatible types: 'String' and 'Int64'
[致命错误] ZCUSERS.dpr(5): Could not compile used unit 'Unit1.pas'

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LPHI数据转换Int64 to String
编程实现
var
  ss,ss1:string;
  ss2:int64;
  tmp:string;
begin
  ss:='AB10000000001';
  tmp:=copy(ss,2,11);
  ss2:=strtoint(tmp)+1;        //如何转换使ss2:=10000000002
  ss1:='AB'+inttostr(ss2);          //结果 ss1:='AB10000000002'
  showmessage(ss1);
end;

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'10000000001' is not a valid integer value

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var
  ss,ss1:string;
begin
  ss:='AB10000000001';
  ss1 := ss;
  ss1[Length(ss1)] := Char(Ord(ss1[Length(ss1)])+1);
  showmessage(ss1);