将所有方法调用“合并”成一个吗？

Question

Let's say I have several classes that essentially do the same thing: process a string and then insert values to a respective table. So essentially, it's a SWICH...CASE statement that looks like the following. The only similarity between all the classes is that the all have a "ProcessString" method.

Now I would like to add some error handling to all these method calls. I can try...catch all the calls, but I was wondering if there's a way to somehow consolidate all these calls, so the that I can call one "ProcessString" at the end of the switch, but that applies to its respective class (sort of like setting a variable to the class name?). That way I can add exception handling to just one call and possibly use reflection to get the class and method being invoked.

switch (strKeyword)
{
    case "KPI_teachers":
        Teachers.processString(strLine, strKeyword, strProcessDate, strProcessHour);
        break;
    case "KPI_students":
        Students.processString(strLine, strKeyword, strProcessDate, strProcessHour);
        break;
    case "KPI_classrooms":
        Classrooms.processString(strLine, strKeyword, strProcessDate, strProcessHour);
        break;
}

Any help is appreciated. Thanks.

Answer 1

It's not necessary to consolidate the switch into a single statement just to handle exceptions, but it's a good exercise anyway.

First of all, you need to give the types backing your properties (I assume they are properties, right?) some common ground from the viewpoint of the type system. That means they need to implement the same interface. Extrapolating from your code, that interface could be

interface IStringProcessor   // a bad name, but all of this is rather abstract
{
    // Those parameter names are highly suspicious -- is string really the
    // correct type for something called "processDate"?
    void ProcessString(string line, string keyword, 
                       string processDate, string processHour);
}

so if you have a property Teachers of type TeacherType , you need to make TeacherType implement IStringProcessor . The same goes for the other two.

Then you want to create a mechanism that maps from a string to an IStringProcessor . That could be some kind of IDictionary , but let's keep it simple for now and make it a method.

private IStringProcessor GetProcessor(string name)
{
    switch (name)
    {
        case "KPI_Teachers": return Teachers;
        case "KPI_Students": return Students;
        case "KPI_Classrooms": return Classrooms;
        default: throw new ArgumentException("blah blah");
    }
}

You now have all the machinery in place to go single-statement:

// The bad naming tradition continues here -- lose the "str" prefix.
// If you forget what `keyword` is and try to do something inappropriate with it
// the compiler will be happy to chastise you.
GetProcessor(strKeyword).processString(...);

Answer 2

This may be way off but:

try 
{
    case "KPI_teachers":
        Teachers.processString(strLine, strKeyword, strProcessDate, strProcessHour);
        break;
    case "KPI_students":
        Students.processString(strLine, strKeyword, strProcessDate, strProcessHour);
        break;
    case "KPI_classrooms":
        Classrooms.processString(strLine, strKeyword, strProcessDate, strProcessHour);
        break;
}
catch (Exception Ex) 
{}
Finally {}