方法的返回类型的目的

Question

I am having issues understanding the syntax of C# Methods - specifically the "must return something" error.

I have this method:

public static class Connection
{
    public static List<string> getClients()
    {   
        List<string> clients = new List<string>();
        return clients;
    }
}

The method is incorrect since I get invalid expression term "return" , so I don't exactly know what to do. Can someone explain me how this public void, etc, works?

Also, why I cant do the following?

public getClients()
    {   
        List<string> clients = new List<string>();
        return clients;
    }

I get an error saying method must have a return type

Answer 1

Every method needs to have a return type, or be declared with a void return type.

If you don't want to return anything, you would have a void return type, like below...

public void printSomething(string something)
{
  System.out.println(something);
}

If you want to return something, you have to declare the return type, like below...

public string returnSomething()
{
  string something = "something";
  return something;
}

So for your example, if you are returning " clients " which is of type List<string> , then you need to declare that return type, like below...

public List<string> getClients()
{
  List<string> clients = new List<string>();
  return clients;
}

Answer 2

What you're working with are called return types . When you define a method, you can set a type (such as integer, Bitmap, string, or even a custom class) to be returned as a value. That way, you can do the following:

int number = Average();

For a method that does not return a value, you can set the void keyword to signify that this method performs actions, but does not get a tangible result. Whereas the Average() method above returns an int when it's finished, a void returns nothing.

Additionally, public and static are keywords are adjectives that describe your method, be it void or not. Public refers to its privacy (or what sections of code can use it) and static refers to the lifetime and reference of a method.

Answer 3

The first piece of code should work.

If you don't want to return anything from a function, make it return void:

public void DoWork() {
    int i = 1 + 1;
} // Don't return anything.

Answer 4

You are getting error saying method must have a return type in the second code because you are not returning a list but the return type is not present in the method signature. For a method with no return type you should use void .

public void method()//void or no return type
{
   //do something
}

Your first code is absolutely fine and should work without error