Question

I am currently learning c# and reading a few books. I can do quite a few things, however only from modifying examples – it really frustrates that I do not actually understand how/why some of the more basic items work.

I have just done a console application that takes arguments and displays them all one by one.

The code is:

using System;

class test
{ static int Main(string[] argsin)
{ 

for (
        int i = 0; 
        i < argsin.Length; 
        i++
    )
Console.WriteLine("Argument: {0}", argsin[i]);
Console.ReadLine();
return -1;
}
}

Now, this works perfectly, but coming from a basic (no pun!) understand of Visual Basic, how/why does it know to print the correct argument and then go on to the next without quitting the application after the first Console.WriteLine… I feel I have missed the fundamentals of how this works!

Next, why is it that inside the for loop, each line ends with a semicolon apart from i++?

I keep forgetting to add it from time to time, and then when trying to work out why it wasn’t compiling, I added one where I wasn’t meant to!

Answer 1

By convention c# and all c like languages when presented with a for loop (or and if statement etc) will run the line immediately after. Personally I don’t like writing code like this, i feel it lacks readability.

To clarify we can add curly braces to denote scope

for (
        int i = 0; 
        i < argsin.Length; 
        i++
    )
{
     Console.WriteLine("Argument: {0}", argsin[i]);
}
Console.ReadLine();
return -1;

now what the for loop executes is clearly defined (and if we wanted to do more in our loop we would add the extra instructions in between the curly braces).

edit:
The reason for the semi colons as you define your for loop is that each part of that definition is a separate statement.

int i = 0; //creates an integer i and sets its value to 0
i < argsin.Length; sets our comparison operation to define when the loop ends
i++ //what to do at the end in this case increment i by 1

Each needs to be treated independent of the others and as the semi colon denotes the end of a statement in c# (which is why each line ends in it) we use it to break up the statements so the compiler can read it.

While the 2 semicolons are mandatory the arguments are not we could if we wanted change it to be this.

int i = 0;
for (;;)
{
     if(i>=argsin.Length){
         break;
     }
     Console.WriteLine("Argument: {0}", argsin[i]);
     i++;
}

This is functionally identical to the way you wrote it but I’ve moved all the logic out of the for statement to its equivalent position inside (or outside in the case of defining i) the loop