Weakly Typed SQL Injection

Programming languages come in two categories:
Hard/Strong Typed
Soft/Weak Typed

Hard Typed languages like Java/C++ demand a developer designate the data type of a variable when writing. Hence the use of types when declaring a variable:

int num = 0;
char letter = '';
private string getUserById(int userId){
    string query = "select * from users 
                        where user_id = " + (string)userId;
    DBConnection connection = new DbUtil()…