project project1.exe raised exception class evarianttypecasterror with message 'could not convert variant of type(null) into type (string)'.process stopped.use step or run to continue.
你在调用数据源时,所取的值是null值,我估计你是这样写的 var str:string; begin str:=ADO**.fieldvalues['***'] end; 你在赋值前先判断一下ADO值是否为空 if ADO**.fieldvalues['**']<>null then begin **** end;
将其进行转化就行了: var str:string; str := ADOQuery1.FieldByName('name').asstring;
var
str:string;
begin
str:=ADO**.fieldvalues['***']
end;
你在赋值前先判断一下ADO值是否为空
if ADO**.fieldvalues['**']<>null then
begin
****
end;
var str:string;
str := ADOQuery1.FieldByName('name').asstring;