Mql4 some qestion about string

[[Deleted]]

string str1; //( is default the str1 is Null or "")

//**********str1 will change during the process

//do something change str1

//end

//check str1

if(str1==NULL) //this will report an ERROR

{

//........

}

please tell me how to know is str1 an null ?

[Alexander]

This is better

if(str1=="")....